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manual small incision cataract surgery versus phacoemulsification WHO evidence

Feature	SICS / MSICS (Manual Small-Incision Cataract Surgery)	Phacoemulsification
Basic technique	Cataract lens nucleus is removed manually through a self-sealing sclero-corneal tunnel.	Ultrasound energy breaks the lens into fragments, which are aspirated.
Incision size	Usually about 5.5-7 mm, sometimes larger depending on nucleus size and technique.	Usually about 2-3 mm.
Need for sutures	Usually sutureless because the tunnel is self-sealing.	Usually sutureless.
Lens removal	Nucleus is delivered manually, for example by viscoexpression, irrigating vectis, or other manual techniques.	Nucleus is emulsified inside the eye and aspirated through a small probe.
IOL used	Often a rigid PMMA posterior-chamber IOL, though foldable IOLs may also be used.	Usually a foldable acrylic or silicone posterior-chamber IOL.
Equipment	Relatively simple instruments; no phaco machine is required.	Requires a phaco machine, ultrasound handpiece, consumables, and reliable maintenance.
Cost	Lower equipment and consumable costs.	Higher capital and consumable cost.
Suitability for dense or mature cataract	Particularly useful for very hard, mature, brunescent, or hypermature cataracts.	Can be more technically demanding in very dense nuclei because of greater ultrasound energy and endothelial risk.
Operating time	Often fast in experienced hands, especially for high-volume settings.	Fast in experienced hands, but time can increase with dense cataracts or machine-related issues.
Postoperative astigmatism	May be somewhat greater because the incision is larger.	Usually less surgically induced astigmatism due to the smaller incision.
Visual recovery	Good visual outcomes; early uncorrected vision may be slightly slower or less predictable than phaco.	Often faster early visual recovery and better early uncorrected visual acuity.
Final best-corrected visual acuity	Generally comparable to phacoemulsification when surgery is uncomplicated.	Generally comparable to SICS when surgery is uncomplicated.
Corneal effect	Less ultrasound-related endothelial stress, but nucleus delivery and larger incision have their own risks.	Ultrasound energy and fluidics can cause corneal endothelial injury or early corneal edema, especially with hard cataracts.
Common intraoperative concerns	Iris prolapse, Descemet membrane detachment, wound-related issues, posterior capsule rupture during manual maneuvers.	Posterior capsule rupture, corneal burn, endothelial cell loss, zonular stress, fluidic surge, retained lens fragments.
Dependence on infrastructure	Low. Suitable where electricity, machine servicing, or consumables are limited.	High. Needs dependable power supply, machine service, and trained support.
Learning curve	Often considered easier to adopt than phaco for surgeons familiar with extracapsular techniques, but still requires structured training.	Steeper learning curve because of foot-pedal control, ultrasound settings, fluidics, and small-incision maneuvers.
Typical setting	High-volume cataract programs and resource-constrained settings.	Well-equipped surgical centers and routine cataract surgery in many higher-resource settings.
Main advantage	Affordable, fast, technology-independent, and effective for dense cataracts.	Very small incision, less induced astigmatism, and often faster early visual rehabilitation.
Main limitation	Larger incision and potentially more surgically induced astigmatism.	Greater cost, machine dependence, and potential ultrasound-related corneal injury.

Bottom line: Both techniques are safe and effective. Phacoemulsification usually offers a small early visual and astigmatic advantage, while SICS is less costly, less dependent on technology, and especially practical for dense cataracts and high-volume settings. Evidence reviews find broadly similar best-corrected visual outcomes after surgery, while resource availability and surgeon expertise often determine the preferred technique. Cochrane comparison and AAO EyeWiki overview support this comparison.

Kanski describes MSICS as a self-sealing sclero-corneal tunnel technique used particularly for high-volume treatment of dense cataracts in less affluent regions. Kanski's Clinical Ophthalmology, 10th ed.

Principles of achieving emmetropia in modern day cataract surgeries- write in detail

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This topic can be organized as:

Meaning and target of emmetropia - refractive goals and acceptable residual error
Preoperative evaluation - ocular surface, refraction, corneal topography, macula and optic nerve
Biometry - axial length, keratometry, anterior chamber depth, lens thickness and effective lens position
IOL power calculation - modern formulas, constant optimization, unusual eye lengths and post-refractive corneas
Astigmatism management - incision planning, toric IOLs, limbal relaxing incisions and posterior corneal astigmatism
IOL selection and targeting - monofocal, toric, multifocal/EDOF, monovision, and patient expectations
Surgical factors - capsulorhexis, IOL centration, wound construction, lens position and complication avoidance
Postoperative assessment and correction - residual refractive error, enhancement options, and causes of refractive surprise

Modern cataract surgery is refractive surgery: the aim is not only a clear visual axis, but a planned postoperative refractive state. Accuracy relies chiefly on reliable ocular measurements, an appropriate IOL formula, control of corneal astigmatism, stable and centered IOL positioning, and realistic selection of the refractive target for the patient.

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Feature	SICS / MSICS (Manual Small-Incision Cataract Surgery)	Phacoemulsification
Basic technique	Cataract lens nucleus is removed manually through a self-sealing sclero-corneal tunnel.	Ultrasound energy breaks the lens into fragments, which are aspirated.
Incision size	Usually about 5.5-7 mm, sometimes larger depending on nucleus size and technique.	Usually about 2-3 mm.
Need for sutures	Usually sutureless because the tunnel is self-sealing.	Usually sutureless.
Lens removal	Nucleus is delivered manually, for example by viscoexpression, irrigating vectis, or other manual techniques.	Nucleus is emulsified inside the eye and aspirated through a small probe.
IOL used	Often a rigid PMMA posterior-chamber IOL, though foldable IOLs may also be used.	Usually a foldable acrylic or silicone posterior-chamber IOL.
Equipment	Relatively simple instruments; no phaco machine is required.	Requires a phaco machine, ultrasound handpiece, consumables, and reliable maintenance.
Cost	Lower equipment and consumable costs.	Higher capital and consumable cost.
Suitability for dense or mature cataract	Particularly useful for very hard, mature, brunescent, or hypermature cataracts.	Can be more technically demanding in very dense nuclei because of greater ultrasound energy and endothelial risk.
Operating time	Often fast in experienced hands, especially for high-volume settings.	Fast in experienced hands, but time can increase with dense cataracts or machine-related issues.
Postoperative astigmatism	May be somewhat greater because the incision is larger.	Usually less surgically induced astigmatism due to the smaller incision.
Visual recovery	Good visual outcomes; early uncorrected vision may be slightly slower or less predictable than phaco.	Often faster early visual recovery and better early uncorrected visual acuity.
Final best-corrected visual acuity	Generally comparable to phacoemulsification when surgery is uncomplicated.	Generally comparable to SICS when surgery is uncomplicated.
Corneal effect	Less ultrasound-related endothelial stress, but nucleus delivery and larger incision have their own risks.	Ultrasound energy and fluidics can cause corneal endothelial injury or early corneal edema, especially with hard cataracts.
Common intraoperative concerns	Iris prolapse, Descemet membrane detachment, wound-related issues, posterior capsule rupture during manual maneuvers.	Posterior capsule rupture, corneal burn, endothelial cell loss, zonular stress, fluidic surge, retained lens fragments.
Dependence on infrastructure	Low. Suitable where electricity, machine servicing, or consumables are limited.	High. Needs dependable power supply, machine service, and trained support.
Learning curve	Often considered easier to adopt than phaco for surgeons familiar with extracapsular techniques, but still requires structured training.	Steeper learning curve because of foot-pedal control, ultrasound settings, fluidics, and small-incision maneuvers.
Typical setting	High-volume cataract programs and resource-constrained settings.	Well-equipped surgical centers and routine cataract surgery in many higher-resource settings.
Main advantage	Affordable, fast, technology-independent, and effective for dense cataracts.	Very small incision, less induced astigmatism, and often faster early visual rehabilitation.
Main limitation	Larger incision and potentially more surgically induced astigmatism.	Greater cost, machine dependence, and potential ultrasound-related corneal injury.

Meaning and target of emmetropia - refractive goals and acceptable residual error
Preoperative evaluation - ocular surface, refraction, corneal topography, macula and optic nerve
Biometry - axial length, keratometry, anterior chamber depth, lens thickness and effective lens position
IOL power calculation - modern formulas, constant optimization, unusual eye lengths and post-refractive corneas
Astigmatism management - incision planning, toric IOLs, limbal relaxing incisions and posterior corneal astigmatism
IOL selection and targeting - monofocal, toric, multifocal/EDOF, monovision, and patient expectations
Surgical factors - capsulorhexis, IOL centration, wound construction, lens position and complication avoidance
Postoperative assessment and correction - residual refractive error, enhancement options, and causes of refractive surprise

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Principles of Achieving Emmetropia in Modern-Day Cataract Surgery

Introduction

Modern cataract surgery is not simply removal of an opaque crystalline lens. It is a refractive procedure in which the surgeon aims to leave the patient with the planned postoperative refractive status, ideally emmetropia.

Emmetropia means that, with accommodation relaxed, parallel rays of light from infinity focus sharply on the retina without spectacles or contact lenses. In pseudophakic cataract surgery, this is generally achieved by replacing the cataractous lens with an intraocular lens (IOL) of accurately calculated power, while also controlling pre-existing and surgically induced astigmatism.

The desired refractive endpoint is not identical for every person. Although plano refraction is often the aim, some patients may deliberately be targeted for mild myopia, monovision, or a presbyopia-correcting IOL strategy. Thus, the practical objective is:

To achieve the patient-specific intended postoperative refraction through precise preoperative measurement, appropriate IOL power calculation and selection, astigmatism correction, atraumatic surgery, and appropriate postoperative management.

Determinants of Postoperative Refraction

The final refractive result depends primarily on:

Axial length of the eye
Corneal refractive power
Anterior chamber depth and predicted effective lens position
Lens thickness
IOL power and design
Corneal astigmatism, including posterior corneal astigmatism
Surgically induced astigmatism
IOL centration, tilt, and postoperative stability
Integrity of the capsular bag and zonules
Accuracy of the IOL formula and lens constant
Ocular surface and corneal regularity
Underlying retinal, macular, optic nerve, or corneal disease

An error in any one of these variables can lead to a postoperative refractive surprise.

1. Define the Refractive Goal Before Surgery

The first principle is to establish a realistic and individualized refractive target.

Common refractive targets

Clinical situation	Usual target
Standard monofocal IOL for distance	Emmetropia or plano
Patient who reads without glasses because of preoperative myopia	Mild myopia may be preferred
Monovision strategy	One eye for distance and the fellow eye for near or intermediate vision
Bilateral multifocal/EDOF IOLs	Usually emmetropia or minimal residual refractive error
Patient with significant retinal disease	Usually monofocal IOL, with a refractive target based on functional needs
High myope accustomed to near vision without spectacles	Avoid an unwanted plano target without detailed counseling

Importance of patient counseling

The patient must understand that cataract surgery cannot guarantee complete spectacle independence in every case. A discussion should cover:

The desired viewing distance: far, intermediate, near, or mixed
Occupational and lifestyle demands
Night driving requirements
Previous spectacle use and visual habits
Tolerance for halos, glare, reduced contrast, and neuroadaptation
Need for reading glasses after monofocal IOL implantation
Possibility of postoperative residual error and enhancement

The ESCRS recommends that target refraction be selected through shared decision-making, taking account of IOL type and patient expectations. ESCRS cataract recommendations

2. Thorough Preoperative Ocular Assessment

A successful refractive outcome begins with identification and treatment of factors that make measurements inaccurate or limit vision despite an accurate refraction.

A. History

Important points include:

Previous refractive surgery: LASIK, PRK, SMILE, radial keratotomy, keratoplasty
Contact lens use, particularly rigid gas-permeable lenses
Trauma or previous intraocular surgery
Glaucoma, uveitis, diabetic retinopathy, macular degeneration
Use of alpha-1 blockers, because of risk of intraoperative floppy iris syndrome
Dry eye symptoms
Previous spectacle prescription and refractive stability
Whether the patient has previously tolerated monovision

Patients using soft contact lenses should discontinue them before measurements. Rigid gas-permeable lenses require a longer cessation period because they can alter corneal shape. Kanski advises approximately one week for soft lenses and up to six weeks for long-term rigid gas-permeable lens wear before stable biometry is obtained. Kanski's Clinical Ophthalmology, 10th ed., Biometry section.

B. Examination

The evaluation should include:

Uncorrected and best-corrected visual acuity
Manifest refraction
Slit-lamp examination
Corneal assessment
Tear-film assessment
Intraocular pressure
Pupil size and iris status
Lens and zonular stability
Dilated retinal and macular examination
Optic nerve examination
Macular OCT when indicated

Posterior segment assessment

A patient may have poor postoperative vision despite accurate IOL calculation if there is:

Diabetic macular edema
Epiretinal membrane
Macular degeneration
Macular hole
Optic atrophy
Advanced glaucomatous damage
Amblyopia

Careful posterior-pole examination is therefore essential before surgery. Kanski's Clinical Ophthalmology, 10th ed., Ophthalmic preoperative assessment.

3. Optimization of the Ocular Surface

The ocular surface is often the most overlooked source of refractive inaccuracy.

Dry eye disease, meibomian gland dysfunction, blepharitis, epithelial basement membrane dystrophy, Salzmann nodular degeneration, and allergic eye disease can produce unstable keratometry readings. This leads to inaccurate spherical IOL power and inaccurate toric IOL calculations.

Principles

Detect ocular surface disease before biometry.
Treat inflammation and tear-film instability.
Repeat keratometry and topography only after stabilization.
Do not select a premium or toric IOL based on inconsistent corneal measurements.

Measures for optimization

Lid hygiene and treatment of blepharitis
Lubricants for dry eye
Treatment of meibomian gland dysfunction
Anti-inflammatory therapy when indicated
Management of allergy
Treatment or removal of significant corneal pathology before final measurements

A stable, regular corneal surface is essential because keratometry is a major determinant of calculated IOL power.

4. Accurate Biometry

Definition

Biometry is the measurement of ocular dimensions required to calculate the IOL power. Modern optical biometers can measure axial length, corneal curvature, anterior chamber depth, white-to-white corneal diameter, and sometimes lens thickness and posterior corneal data.

Kanski notes that modern optical biometry devices perform keratometry, anterior chamber depth, and white-to-white measurements, and calculate IOL power using multiple formulae. Kanski's Clinical Ophthalmology, 10th ed., Biometry section.

A. Axial length

Axial length is the distance from the anterior corneal surface to the retina, generally the fovea. It is one of the most influential variables in IOL power calculation.

Significance of axial length error

Even a small axial-length error can cause clinically meaningful postoperative refractive error. Therefore:

Verify good fixation.
Ensure repeatability of readings.
Compare both eyes for biologically plausible symmetry.
Investigate major inter-eye disparity.
Use immersion ultrasound when optical biometry is not possible.

Optical biometry

Optical biometry is preferred in most eyes because it is:

Non-contact
Highly reproducible
Rapid
Less dependent on operator technique
Able to use fixation information
Able in some instruments to identify macular pathology or poor fixation

Swept-source optical coherence tomography biometers have improved measurement through denser cataracts compared with older partial-coherence interferometry devices. ESCRS discussion of OCT biometry

Ultrasound biometry

Ultrasound biometry is useful when optical biometry fails, such as with:

Dense mature cataract
Dense posterior subcapsular opacity
Vitreous hemorrhage
Severe corneal opacity
Poor fixation

Immersion A-scan is preferred over contact A-scan because corneal indentation during contact measurement can falsely shorten the axial length and cause a postoperative hyperopic outcome.

B. Keratometry

Keratometry measures anterior corneal curvature and estimates corneal power.

Accuracy requires:

A smooth tear film
Regular astigmatism
Stable fixation
Reproducible readings
Correlation between keratometry, corneal topography, tomography, and manifest refraction where appropriate

When keratometry differs substantially among devices, the surgeon should not blindly accept one value. The cause should be identified, such as dry eye, irregular cornea, contact lens warpage, keratoconus, or previous corneal surgery.

C. Anterior chamber depth and lens thickness

Anterior chamber depth and lens thickness help predict the final location of the IOL within the eye. This is called the effective lens position.

The actual postoperative position of an IOL cannot be known perfectly before surgery. Modern formulas estimate it using multiple ocular parameters. Error in prediction of effective lens position is a major source of residual refractive error, especially in short or long eyes.

5. Appropriate IOL Power Calculation Formula

A. The aim of the formula

IOL formulas combine biometric data to estimate the IOL power needed to achieve a chosen postoperative refraction.

Traditional formulas chiefly use:

Axial length
Keratometry
An estimated effective lens position

Modern formulas may also incorporate:

Anterior chamber depth
Lens thickness
White-to-white diameter
Corneal diameter
Posterior corneal power
Artificial intelligence or ray-tracing principles
Total keratometry measurements

B. Evolution of formulas

Third-generation formulas

Examples include:

SRK/T
Hoffer Q
Holladay 1

These largely predict effective lens position from axial length and keratometry.

Fourth-generation formulas

Examples include:

Haigis
Holladay 2
Barrett Universal II
Olsen

These incorporate additional variables, such as anterior chamber depth, lens thickness, or white-to-white diameter.

New-generation formulas

Examples include:

Barrett Universal II
Kane formula
EVO formula
Hill-RBF formula
PEARL-DGS formula
Olsen formula

These show less systematic error across a range of axial lengths than older formulas. ESCRS guidance recognizes a tendency toward better consistency with newer-generation formulas, although conventional formulas may remain acceptable when modern formulas are unavailable. ESCRS guidance on IOL calculations

C. Use more than one formula

For routine cases, it is prudent to compare predictions from more than one validated modern formula. If one formula differs substantially from the others, possible causes should be reviewed:

Incorrect biometry
Unstable keratometry
An unusual axial length
Prior corneal refractive surgery
Abnormal anterior chamber depth
Incorrect IOL constant
Use of an unsuitable formula

The final selected power should be clinically sensible and not based solely on a software output.

6. IOL Constants and Their Optimization

An IOL constant is a lens-specific value used by an IOL formula to estimate its postoperative position and refractive behavior.

Different formulas use different constants, for example:

A-constant
Surgeon factor
Lens factor
ACD constant

Principles of constant optimization

Use the correct constant for the exact IOL model.
Use constants appropriate to the biometer and formula.
Prefer optimized constants from reliable databases or personal surgical outcomes.
Audit postoperative refractive results regularly.
Adjust the surgeon-specific constant when a consistent myopic or hyperopic trend is demonstrated.

Constant optimization transforms a generic calculation into a surgeon- and technique-specific calculation. It accounts for subtle but consistent differences in incision, capsulorhexis, lens placement, biometry device, and IOL behavior.

7. Management of Corneal Astigmatism

Achieving spherical emmetropia alone is inadequate if significant corneal astigmatism remains. Residual astigmatism reduces uncorrected distance vision, causes blur or ghosting, and decreases satisfaction with premium IOLs.

A. Determine whether astigmatism is regular

Regular astigmatism

Regular corneal astigmatism may be managed with:

Incision placement
Opposite clear corneal incisions
Limbal relaxing incisions or arcuate keratotomy
Toric IOL implantation

Irregular astigmatism

Irregular astigmatism may arise from:

Keratoconus
Pellucid marginal degeneration
Corneal scars
Previous corneal surgery
Ocular surface disease
Corneal dystrophy

A toric IOL may not reliably correct irregular astigmatism. The underlying corneal condition should first be evaluated and treated where possible.

B. Consider posterior corneal astigmatism

Anterior keratometry alone does not represent total corneal astigmatism. The posterior corneal surface can influence total magnitude and axis.

Ignoring posterior corneal astigmatism may lead to toric overcorrection or undercorrection, particularly in against-the-rule astigmatism. Modern toric calculators attempt to account for posterior corneal astigmatism, effective lens position, and surgically induced astigmatism.

For toric IOL planning, ESCRS recommends corneal topography and/or tomography, and prefers methods that incorporate posterior corneal astigmatism and effective lens position. ESCRS toric IOL recommendations

C. Incision planning

A corneal incision can flatten the meridian on which it is placed. Therefore:

Place the main incision on the steep meridian when mild astigmatism correction is intended.
Use a small, reproducible incision.
Use a consistent incision location and architecture.
Incorporate the surgeon's personal surgically induced astigmatism into toric calculations.

Large, poorly constructed, or sutured wounds can induce substantial astigmatism and undermine an otherwise accurate IOL calculation.

D. Toric IOLs

Toric IOLs are the most predictable method of correcting regular corneal astigmatism during cataract surgery.

Requirements for a good toric outcome

Stable and repeatable keratometry
Regular astigmatism
Accurate corneal axis determination
Accurate marking or image-guided alignment
Correct toric power calculation
Appropriate adjustment for posterior corneal astigmatism
Precise IOL alignment
Adequate capsular support

Rotation of a toric IOL reduces its astigmatic correction. Approximately every 1 degree of IOL rotation from its intended axis reduces the effective cylinder correction by about 3.3%; rotation of 30 degrees essentially nullifies the intended correction.

ESCRS states that toric IOLs should be considered with regular corneal astigmatism of 1.0 D or more, with stronger evidence at higher levels of astigmatism. ESCRS cataract guideline

8. Choice of IOL Type

A. Monofocal IOL

A monofocal IOL provides one principal focal point, usually set for distance.

Advantages:

Good distance quality of vision
Better contrast sensitivity than many multifocal designs
Fewer halos and glare phenomena
Suitable for patients with macular or optic nerve disease

Limitations:

Reading glasses are usually needed for near tasks.
Intermediate glasses may also be needed.

A monofocal IOL is often the safest option when visual potential is limited or the patient is intolerant of optical phenomena.

B. Toric monofocal IOL

This corrects regular corneal astigmatism while maintaining monofocal optics. It is particularly useful in patients who desire good unaided distance vision and have significant regular astigmatism.

C. Multifocal and trifocal IOLs

These provide multiple focal points and can reduce dependence on spectacles for distance and near vision.

However, they may cause:

Halos
Glare
Starbursts
Reduced contrast sensitivity
Night-driving difficulty
Dissatisfaction if there is residual refractive error or ocular pathology

Careful selection is essential. Significant dry eye, irregular astigmatism, macular pathology, glaucoma with central field loss, corneal opacity, or unrealistic expectations may make these lenses unsuitable.

D. Extended-depth-of-focus IOLs

EDOF lenses aim to provide a continuous range of vision, particularly distance and intermediate vision, with fewer dysphotopsias than some multifocal IOLs. Near spectacle independence may still be incomplete.

E. Monovision and mini-monovision

In monovision, the dominant eye is targeted for distance and the non-dominant eye for near vision. Mini-monovision generally uses a smaller anisometropic difference, providing distance in one eye and intermediate vision in the other.

Success depends on:

Previous tolerance of monovision, ideally with a contact lens trial in uncertain cases
Ocular dominance
Binocular function
Occupation and driving needs
Patient understanding of compromises in stereoacuity and night vision

9. Precision in Surgical Technique

An accurate preoperative plan can fail if surgery changes corneal shape or IOL position.

A. Wound construction

The incision should be:

Small
Self-sealing
Reproducible
Properly positioned
Free from excessive thermal injury
Free from wound leak

Poor wound architecture may cause induced astigmatism, instability, hypotony, infection risk, or a changing early postoperative refraction.

B. Capsulorhexis

A well-centered, appropriately sized continuous curvilinear capsulorhexis is central to long-term refractive stability.

It should:

Overlap the IOL optic circumferentially where possible
Maintain IOL centration
Reduce anterior capsular fibrosis effects
Help prevent lens tilt and decentration
Promote stable effective lens position

An excessively large, eccentric, or incomplete capsulorhexis can result in IOL decentration, tilt, capsular contraction-related displacement, and refractive error.

C. In-the-bag IOL fixation

The preferred location for most posterior chamber IOLs is the capsular bag. This provides the most predictable effective lens position and stability.

Sulcus fixation, optic capture, anterior chamber IOLs, and scleral-fixated IOLs may be necessary in complicated cases, but they have less predictable effective lens positions. The IOL power often needs adjustment when a lens is not placed in the intended location.

D. IOL centration and tilt

IOL decentration or tilt can produce:

Refractive error
Induced astigmatism
Higher-order aberrations
Glare and dysphotopsia
Poor multifocal IOL performance

This is especially important in multifocal, EDOF, and toric IOLs.

E. Avoid intraoperative complications

Posterior capsular rupture, zonular dialysis, vitreous loss, dropped nucleus, wound burn, and retained lens material can all compromise the planned IOL position and the postoperative refractive result.

Careful case selection, adequate pupil dilation, capsular support devices when required, and sound phacoemulsification technique are refractive as well as safety measures.

10. Special Situations

A. Very short eyes and nanophthalmos

Short eyes have:

High-power IOL requirements
Greater effect of small errors in effective lens position
Shallow anterior chamber
Higher likelihood of refractive surprise

Use reliable modern formulas and consider comparing multiple formula outputs. ESCRS supports use of new-generation formulas in extreme short and long eyes. ESCRS IOL calculation guidance

B. Long eyes and high myopia

Long eyes may have:

Posterior staphyloma
Fixation difficulty
Greater risk of axial-length measurement error
A tendency toward hyperopic surprise with some older methods

Confirm foveal fixation, compare formulas, and use a modern formula suitable for long eyes.

C. Previous corneal refractive surgery

Post-LASIK, PRK, SMILE, and radial keratotomy eyes are difficult because corneal refractive surgery alters the relationship between anterior corneal curvature and total corneal power. Standard keratometry and standard IOL formulas can therefore be inaccurate.

Principles include:

Obtain prior refractive data if available.
Use topography and tomography.
Use total keratometry where available.
Use dedicated post-refractive IOL calculation methods.
Compare several post-refractive formulae.
Counsel the patient about increased uncertainty and possible enhancement.

ESCRS recommends designated post-refractive calculation methods, such as the ASCRS post-refractive calculator. ESCRS guidance

D. Keratoconus and irregular cornea

In keratoconus:

Determine whether the cornea is stable.
Identify the true central corneal power.
Use tomography rather than relying only on conventional keratometry.
Avoid multifocal IOLs in most cases.
Consider toric IOLs only in selected eyes with stable, sufficiently regular astigmatism.

E. Macular and optic nerve disease

The presence of macular disease does not necessarily prevent accurate refraction, but it limits visual benefit and may contraindicate multifocal IOLs. A monofocal lens with a realistic refractive aim is often preferable.

11. Prevention, Evaluation, and Management of Refractive Surprise

A refractive surprise is a clinically significant difference between the intended and actual postoperative refraction.

Kanski identifies inaccurate biometry as the commonest cause. Kanski's Clinical Ophthalmology, 10th ed., Refractive surprise section.

A. Causes

Preoperative causes

Incorrect axial length
Incorrect keratometry
Tear-film instability
Contact lens-induced corneal warpage
Incorrect IOL constant
Inappropriate formula
Failure to account for previous refractive surgery
Wrong target entered into the calculator
Incorrect toric axis or cylinder planning

Intraoperative causes

Wrong IOL implanted
Wrong IOL placement, such as sulcus rather than bag
Posterior capsular rupture
IOL tilt or decentration
Excessive surgically induced astigmatism
Toric IOL misalignment
Capsular bag instability

Postoperative causes

Toric IOL rotation
IOL displacement
Capsular contraction
Cystoid macular edema causing refractive change
Corneal edema or remodeling
Posterior capsular opacification
Ocular surface disease

B. Evaluation

The evaluation includes:

Manifest and subjective refraction
Slit-lamp assessment of IOL centration and capsular bag
Assessment of toric IOL axis
Corneal topography or tomography
Repeat biometry and keratometry
Verification of implanted IOL model and power
Assessment of retinal and macular pathology, including OCT when needed

Kanski advises identifying the cause, obtaining a subjective refraction, examining for conditions such as capsular-bag distension and cystoid macular edema, checking the implanted IOL power, and repeating biometry and keratometry when required. Kanski's Clinical Ophthalmology, 10th ed., Management of refractive surprise.

C. Management options

The choice depends on the magnitude and cause of residual error, corneal status, IOL position, patient expectations, and time since surgery.

Method	Typical role
Spectacles	Safest option for small errors or low-demand patients
Contact lenses	Useful for irregular astigmatism or larger errors
Toric IOL rotation	For early significant toric IOL misalignment
Corneal laser enhancement	Suitable for stable cornea and suitable residual sphere/cylinder
Limbal relaxing incision/arcuate keratotomy	Selected residual astigmatism
IOL exchange	Large early error, wrong IOL, or unsuitable IOL
Piggyback IOL	Selected large residual refractive error when exchange is risky

12. Practical Stepwise Approach to Achieving Emmetropia

Preoperative stage

Establish the patient's visual priorities and refractive goal.
Document refraction, ocular dominance, and spectacle history.
Perform detailed ocular examination.
Treat dry eye and ocular-surface disease before final measurements.
Discontinue contact lenses for an appropriate period.
Obtain repeatable optical biometry.
Verify axial length and keratometry.
Perform corneal topography or tomography if astigmatism is significant, irregular, or a toric IOL is planned.
Assess the macula and optic nerve.
Use appropriate modern IOL formulas.
Optimize the IOL constant.
Plan astigmatism treatment, including posterior corneal astigmatism and surgically induced astigmatism.
Counsel about likely spectacle dependence, dysphotopsias, limitations, and possible enhancements.

Intraoperative stage

Confirm correct patient, eye, IOL model, IOL power, and toric axis.
Create a small, reproducible incision.
Perform a well-centered capsulorhexis of appropriate size.
Preserve capsular and zonular integrity.
Implant the IOL securely in the capsular bag whenever possible.
Remove viscoelastic from behind the IOL to reduce postoperative rotation.
Precisely align the toric IOL.
Ensure wound integrity and minimize induced astigmatism.

Postoperative stage

Assess visual acuity and refraction after stabilization.
Examine IOL centration, tilt, and toric axis.
Treat ocular surface disease or inflammation.
Investigate any discrepancy between intended and achieved refraction.
Consider conservative correction first.
Offer a surgical enhancement only after the refraction and cornea are stable and the cause has been identified.

Conclusion

Achievement of emmetropia after cataract surgery is the result of a chain of accurate steps rather than a single calculation. The key principles are:

Individualize the target refraction
Optimize the ocular surface
Obtain reliable biometry
Use suitable modern IOL formulas and optimized lens constants
Correct clinically significant corneal astigmatism
Select the IOL according to ocular health and patient expectations
Perform precise, low-astigmatism surgery with stable in-the-bag IOL fixation
Recognize, investigate, and manage residual refractive error systematically

The aim should be not merely an anatomically successful cataract operation, but a predictable, stable, patient-satisfactory refractive outcome.

Long note on types, clinical features and management of metabolic cataract

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Metabolic Cataract: Types, Clinical Features and Management

Definition

A metabolic cataract is lens opacity produced by a systemic metabolic or endocrine abnormality. It may occur in infancy, childhood, adolescence, or adulthood, and is often bilateral. In some disorders, especially galactosemia, cataract may be an early clue to a serious systemic disease and requires urgent treatment.

The lens is avascular and depends on tightly controlled hydration, electrolyte balance, glucose metabolism, and protein stability to remain transparent. Metabolic disturbances can cause:

Accumulation of osmotically active substances, such as sorbitol or galactitol
Water influx and swelling of lens fibers
Formation of vacuoles and cortical opacities
Oxidative injury and protein denaturation
Deposition of substances such as copper or glycosphingolipids
Disturbance of calcium and electrolyte homeostasis

Classification

A. Carbohydrate metabolism disorders

Diabetes mellitus
Galactosemia
- Classic galactosemia: galactose-1-phosphate uridyltransferase (GALT) deficiency
- Galactokinase (GALK) deficiency
- UDP-galactose-4-epimerase (GALE) deficiency
Hereditary fructose intolerance and other rare carbohydrate disorders

B. Calcium and endocrine disorders

Hypocalcemia
Hypoparathyroidism
Pseudohypoparathyroidism
Occasionally, severe and prolonged metabolic imbalance in other endocrine disorders

C. Disorders of lipid and storage metabolism

Fabry disease
Cerebrotendinous xanthomatosis
Some lysosomal storage disorders and mucopolysaccharidoses

D. Disorders of metal metabolism

Wilson disease

E. Metabolic disorders associated with characteristic cataracts but often classified separately

Myotonic dystrophy
Atopic disease
Neurofibromatosis type 2
Down syndrome

The core exam-relevant metabolic cataracts are usually diabetic cataract, galactosemic cataract, hypocalcemic cataract, Wilson sunflower cataract, and Fabry cataract.

Pathogenesis of Metabolic Cataract

General mechanisms

1. Osmotic lens damage

The most important mechanism in diabetes and galactosemia is accumulation of an osmotically active sugar alcohol within lens fibers.

In diabetes, glucose is converted to sorbitol.
In galactosemia, galactose is converted to galactitol.

These substances do not diffuse readily out of the lens. Their accumulation increases intracellular osmotic pressure, causing:

Entry of water into lens fibers
Hydropic swelling
Vacuole formation
Disruption of lens-fiber architecture
Opacification of the lens

2. Oxidative stress and protein alteration

Chronic hyperglycemia and some systemic metabolic disorders promote oxidative stress, glycation of lens proteins, and damage to antioxidant defense systems. Lens crystallins lose their normal arrangement and transparency.

3. Disturbance of calcium homeostasis

Chronic hypocalcemia affects lens metabolism and cell membrane function. It leads to characteristic cortical opacities and, with prolonged disease, established cataract.

4. Deposition of abnormal metabolites

Copper deposition occurs in Wilson disease.
Glycosphingolipid accumulation occurs in Fabry disease.
These may produce characteristic appearances, sometimes with little visual impairment.

1. Diabetic Cataract

Definition

Diabetic cataract refers to cataract formation associated with diabetes mellitus. Diabetes can cause:

Transient refractive changes due to fluctuating lens hydration and refractive index
Earlier onset and faster progression of age-related cataract
The rare, classical snowflake cataract

Kanski notes that classical diabetic cataract consists of snowflake cortical opacities in young people and may mature over a few days or sometimes resolve spontaneously. Diabetes also predisposes to earlier age-related cataract, especially rapidly progressive nuclear sclerosis. Kanski's Clinical Ophthalmology, 10th ed.

Pathogenesis

In hyperglycemia:

[ \text{Glucose} \xrightarrow[\text{aldose reductase}]{ } \text{Sorbitol} ]

Sorbitol accumulates in the lens because its metabolism is limited. This produces osmotic overhydration of lens fibers.

Consequences include:

Altered lens refractive index
Fluctuation in refractive error
Cortical fluid vacuoles
Swelling and disruption of lens fibers
Cortical opacification
Oxidative stress and protein glycation in chronic diabetes

Increased lens sorbitol and fructose concentrations have been associated with diabetic cataract. Harper's Illustrated Biochemistry, 32nd ed.

Clinical features

A. Refractive fluctuation

Rapid changes in plasma glucose can alter the lens refractive index.

Hyperglycemia may produce a myopic shift
Falling blood glucose may produce relative hyperopia
The patient may complain that glasses “suddenly no longer work”

A stable refraction should be deferred until glycemic control has stabilized.

B. Typical diabetic cataract

The classical diabetic or metabolic cataract is:

Rare
Usually bilateral
More common in children, adolescents, and young adults with poorly controlled type 1 diabetes
Sometimes the presenting sign of diabetes
Rapidly progressive

C. Slit-lamp appearance

The classical appearance is:

Multiple superficial cortical vacuoles
White punctate or flaky cortical opacities
Snowflake cataract
Rapid coalescence of opacities into diffuse cortical cataract

D. Other ocular features of diabetes

The patient should also be evaluated for:

Nonproliferative or proliferative diabetic retinopathy
Diabetic macular edema
Neovascular glaucoma
Ocular surface disease
Cranial nerve palsy
Refractive instability

Management

1. Systemic control

Refer for diabetes assessment and optimization.
Check for diabetic ketoacidosis or hyperosmolar state if newly diagnosed or systemically ill.
Improve glycemic control gradually and safely.
Control hypertension, dyslipidemia, and renal disease.

Correction of hyperglycemia may stabilize refraction and, in rare early cases, may allow partial clearing of osmotic lens changes. However, established cataract generally does not reverse.

2. Ophthalmic management

Record best-corrected visual acuity and refraction.
Perform dilated retinal examination.
Obtain macular OCT if diabetic macular edema is suspected.
Treat sight-threatening retinopathy or macular edema appropriately before or around cataract surgery.
Delay final IOL power calculation until refraction and corneal measurements are stable.

3. Cataract surgery

Indications are the same as for other cataracts:

Visual impairment affecting daily activity
Inability to examine or treat diabetic retinopathy adequately
Lens-induced complications, rarely
A visually significant dense cataract

Phacoemulsification with posterior chamber IOL implantation is usual. Important considerations are:

Optimize glycemic control where feasible.
Assess and document retinopathy and macular status.
Counsel that visual outcome depends greatly on retinal status.
Monitor for postoperative macular edema and retinopathy progression.

2. Galactosemic Cataract

Definition

Galactosemia comprises inherited defects in galactose metabolism. The clinically important enzyme defects include:

Disorder	Enzyme deficiency	Usual systemic severity
Classic galactosemia	GALT deficiency	Severe neonatal systemic disease
Galactokinase deficiency	GALK deficiency	Cataract may be the principal or only manifestation
Epimerase deficiency	GALE deficiency	Variable, from mild to severe disease

Pathogenesis

Lactose in milk is broken down into glucose and galactose. In galactose metabolism disorders, galactose cannot be properly metabolized.

Excess galactose is reduced by aldose reductase to galactitol:

[ \text{Galactose} \xrightarrow[\text{aldose reductase}]{ } \text{Galactitol} ]

Galactitol is osmotically active and poorly diffusible. It accumulates in lens fibers, causing water entry, swelling, vacuolization, and cataract.

GeneReviews describes galactitol as an impermeant alcohol that increases intracellular osmolality and causes water imbibition by lens fibers. GeneReviews on galactosemia

Clinical features

A. Time of presentation

Usually in neonates or early infancy after exposure to breast milk or lactose-containing formula
May occasionally present later, particularly in partial enzyme defects
Usually bilateral

B. Classical lens appearance

The characteristic cataract is:

Oil-droplet cataract
Central, rounded, yellowish or brownish opacity
Often associated initially with cortical vacuoles
May progress rapidly to total cataract if untreated

The oil-droplet appearance may not always be present. The Wills Eye Manual notes that galactosemic cataract morphology and age of onset vary, and the typical oil-droplet opacity may or may not be seen.

C. Systemic features of classic galactosemia

A newborn may have:

Poor feeding
Vomiting
Failure to thrive
Jaundice
Hepatomegaly
Liver dysfunction or cirrhosis
Hypoglycemia
Coagulopathy
Lethargy
Increased risk of Escherichia coli sepsis
Developmental delay if untreated

D. Galactokinase deficiency

In GALK deficiency:

Cataract can be the main or only clinical feature.
Severe liver disease is usually absent.
Cataract may present in infancy or childhood.

This distinction is important because a child with bilateral cataracts may appear otherwise well but still require urgent metabolic evaluation.

Diagnosis

Investigations include:

Newborn screening results
Erythrocyte GALT enzyme activity
Erythrocyte galactose-1-phosphate
Blood or urine galactose and galactitol where available
Molecular genetic testing
Liver function tests
Blood glucose
Sepsis evaluation in an ill newborn

Recent blood transfusion can affect erythrocyte enzyme assay results. Genetic testing and parental enzyme assays may be useful in selected circumstances. Inherited metabolic eye disease review

Management

1. Immediate dietary treatment

If galactosemia is suspected, treatment should begin without waiting for confirmatory testing.

Stop breast milk and lactose-containing feeds.
Use lactose-free, galactose-restricted formula.
Institute long-term dietary galactose restriction after diagnostic confirmation.
Involve a pediatrician, metabolic physician, dietitian, and genetic counselor.

Early dietary restriction may prevent progression and can permit regression of early cataract. The literature notes that early oil-drop cataracts may resolve if a galactose-free diet is introduced promptly. Inherited metabolic eye disease review

2. Ophthalmic observation

Small peripheral or early opacities may be observed if:

The red reflex is present
The visual axis is clear
Fixation is central and maintained
There is no developing amblyopia

Frequent follow-up is necessary.

3. Cataract surgery

Surgery is indicated if:

The opacity blocks the visual axis
The red reflex is absent or significantly reduced
There is a risk of deprivation amblyopia
The cataract progresses despite dietary treatment

In infants, visual rehabilitation after surgery is as important as surgery itself:

Aphakic correction with contact lens or spectacles
Primary IOL only in carefully selected cases
Amblyopia therapy, including occlusion when needed
Close follow-up for visual development, glaucoma, and posterior capsular opacification

Goldman-Cecil notes that galactosemic cataract can be reversible with dietary restriction, whereas dense vision-obstructing cataracts require early removal to prevent amblyopia.

3. Hypocalcemic Cataract

Causes

Hypocalcemic cataract occurs in prolonged hypocalcemia, most commonly due to:

Hypoparathyroidism
Pseudohypoparathyroidism
Post-thyroidectomy hypoparathyroidism
Vitamin D deficiency or resistance, in selected cases
Chronic renal disease with mineral imbalance
Other chronic disorders of calcium-phosphate metabolism

Pathogenesis

Persistent low calcium disrupts normal lens epithelial and fiber-cell metabolism, membrane function, and protein stability. The exact mechanism is multifactorial. Lens changes may progress slowly with chronic untreated hypocalcemia.

Clinical features

Ocular appearance

Typical slit-lamp findings are:

Small, white, punctate cortical opacities
Iridescent or shimmering cortical deposits
Usually bilateral
Initially peripheral, later may become confluent and visually significant

The Wills Eye Manual describes hypocalcemic cataract as small, white, iridescent cortical changes, often in the setting of tetany.

Systemic features

Search specifically for symptoms and signs of hypocalcemia:

Perioral tingling
Paresthesias of hands and feet
Muscle cramps
Carpopedal spasm
Tetany
Seizures
Fatigue
Psychiatric symptoms
Prolonged QT interval
History of neck surgery

Clinical signs may include:

Chvostek sign
Trousseau sign

Features of chronic hypoparathyroidism may include dental abnormalities, basal ganglia calcification, and neuropsychiatric manifestations.

Investigations

Serum total calcium corrected for albumin
Ionized calcium
Serum phosphate
Magnesium
Parathyroid hormone
25-hydroxyvitamin D
Renal function tests
ECG if symptomatic or severe hypocalcemia
CT brain when clinically indicated for basal ganglia calcification

Management

1. Treat the underlying calcium disorder

Management requires coordination with endocrinology or internal medicine.

Acute symptomatic hypocalcemia may require intravenous calcium.
Chronic hypoparathyroidism is generally treated with oral calcium and active vitamin D analogues, according to endocrinology guidance.
Correct associated magnesium deficiency.
Treat renal or vitamin D-related causes where relevant.

2. Ophthalmic management

Small non-central opacities can be observed.
Correct any associated refractive error.
Cataract surgery is indicated for visually significant cataract.

Correction of hypocalcemia may prevent further progression, but established opacities often do not completely clear.

4. Wilson Disease: Sunflower Cataract

Definition

Wilson disease is an inherited disorder of copper transport resulting in toxic copper accumulation, principally in the liver, brain, cornea, and other tissues.

Lens appearance

The classic lens finding is the sunflower cataract:

Central disc-like anterior capsular opacity
Fine radiating petal-like spokes
Brown, greenish, or red-brown coloration
Copper deposition beneath the anterior lens capsule and in the anterior cortex

The Wills Eye Manual describes red-brown pigment deposition in the anterior cortical lens beneath the anterior capsule, called a sunflower cataract.

Clinical relevance

Sunflower cataract:

Is often detected on slit-lamp examination
May be bilateral
Usually causes little or no visual impairment
Should not be confused with a visually significant senile cataract
Is usually accompanied by, or may occur with, Kayser-Fleischer rings

Other systemic findings include:

Hepatitis, cirrhosis, or liver failure
Tremor
Dysarthria
Dystonia
Psychiatric manifestations
Hemolytic anemia

Management

Refer urgently for evaluation and treatment of Wilson disease.
Systemic therapy includes copper chelation or zinc-based therapy under specialist supervision.
Sunflower cataract often regresses with successful chelation treatment.
Cataract extraction is rarely needed solely for sunflower cataract because vision is usually unaffected.

A gastroenterology reference notes that sunflower cataract does not usually interfere with vision and may disappear with chelation therapy. Sleisenger and Fordtran's Gastrointestinal and Liver Disease, Ocular Signs section.

5. Fabry Cataract

Definition

Fabry disease is an X-linked lysosomal storage disorder caused by deficient alpha-galactosidase A activity. It leads to accumulation of globotriaosylceramide and related glycosphingolipids in multiple organs.

Lens appearance

The characteristic lens opacity is:

Fabry cataract
Posterior subcapsular, wedge-shaped, or spoke-like opacity
Often described as a propeller-like or radial pattern
Usually bilateral

Kanski describes Fabry cataract as a wedge- or spoke-shaped posterior cataract.

Associated ocular findings

Cornea verticillata
Conjunctival vessel tortuosity
Retinal vessel tortuosity
Aneurysmal conjunctival vessel changes

Systemic features

Episodic burning pain in hands and feet, acroparesthesias
Angiokeratomas
Hypohidrosis
Gastrointestinal symptoms
Renal impairment
Cardiomyopathy
Arrhythmias
Stroke risk

Management

Refer for metabolic/genetic evaluation.
Enzyme replacement therapy or pharmacological chaperone therapy may be appropriate in selected patients under specialist care.
The lens opacity is often mild and does not usually require cataract surgery.
Treat cataract surgically only if visual impairment is attributable to a significant lens opacity.

6. Other Metabolic and Systemic Conditions

A. Myotonic dystrophy

Although often grouped under systemic rather than purely metabolic cataract, it is an important examination entity.

Appearance

Christmas-tree cataract
Fine multicolored, iridescent, needle-like crystalline opacities
Usually located beneath the anterior capsule
May later develop typical cortical or posterior subcapsular opacity

Associated features

Myotonia
Distal muscle weakness
Frontal balding
Cardiac conduction defects
Endocrine abnormalities

Management

Neurologic and cardiac assessment
Cataract surgery for visual impairment
Careful anesthetic planning due to systemic disease

B. Cerebrotendinous xanthomatosis

This rare lipid-storage disorder may present with juvenile cataracts.

Associated features may include:

Chronic diarrhea in infancy
Tendon xanthomas
Progressive neurologic decline
Ataxia
Cognitive impairment

Management requires metabolic specialist involvement. Early disease-specific therapy may prevent neurologic progression.

C. Mucopolysaccharidoses and other storage disorders

These more commonly produce corneal clouding but can be associated with lens changes. Look for:

Coarse facial features
Skeletal abnormalities
Developmental delay
Hepatosplenomegaly
Corneal clouding

D. Atopic dermatitis

Atopic cataract is not strictly metabolic but is classically associated with systemic disease.

Anterior subcapsular shield-like opacity may occur.
Posterior subcapsular cataract may also be seen.
It can occur in young people with severe atopic dermatitis.

E. Neurofibromatosis type 2

Posterior subcapsular cataract can occur in young patients.
Search for vestibular schwannoma, hearing loss, and other neurologic signs.

Clinical Approach to a Patient With Suspected Metabolic Cataract

History

Ask about:

Age at onset of visual symptoms
Bilaterality and rapidity of progression
Diabetes symptoms: polyuria, polydipsia, weight loss
Neonatal feeding difficulty, jaundice, vomiting, failure to thrive
History of seizures, tetany, muscle cramps, neck surgery
Liver disease or neurologic symptoms
Family history of childhood cataract, metabolic disease, consanguinity, unexplained neonatal deaths
Drug history, particularly corticosteroids
Previous ocular trauma, uveitis, or radiation exposure

Ocular examination

Perform:

Visual acuity assessment
Cycloplegic refraction in children
Red reflex assessment in infants
Slit-lamp examination to determine morphology
Intraocular pressure measurement
Dilated fundus examination
Macular OCT when needed
B-scan ultrasonography if the fundus cannot be seen

Systemic evaluation

The systemic work-up depends on age and morphology.

Cataract morphology or setting	Important investigations
Snowflake cortical cataract in young person	Blood glucose, HbA1c, ketones if symptomatic
Oil-droplet cataract in infant	Galactosemia screen, GALT activity, galactose-1-phosphate, liver function tests
Iridescent cortical opacities with tetany	Calcium, phosphate, PTH, vitamin D, magnesium
Sunflower cataract	Liver function tests, ceruloplasmin, urinary copper, slit-lamp search for Kayser-Fleischer ring
Spoke-like posterior opacity with cornea verticillata	Fabry enzyme assay and genetic assessment
Bilateral childhood cataract with systemic features	Pediatric and metabolic evaluation, genetic testing where appropriate

In a child with bilateral cataract and systemic symptoms, a metabolic pediatric consultation is important. StatPearls pediatric cataract review

Principles of Management

1. Treat the systemic disease promptly

The first priority is correction of the underlying metabolic disturbance. This may:

Prevent cataract progression
Reverse early osmotic lens changes in selected conditions
Prevent severe systemic morbidity
Improve perioperative safety
Reduce recurrence or progression in the fellow eye

Examples:

Glycemic control in diabetes
Immediate galactose restriction in suspected galactosemia
Calcium and vitamin D therapy in hypocalcemia or hypoparathyroidism
Chelation or zinc treatment in Wilson disease
Enzyme-targeted treatment in Fabry disease where indicated

2. Assess whether the cataract is reversible or progressive

Potentially reversible or partially reversible early cataracts include:

Early galactosemic cataract after prompt dietary treatment
Early diabetic osmotic changes after correction of hyperglycemia
Wilson sunflower cataract after copper-lowering therapy

Established dense cataracts usually need surgery if visually significant.

3. Prevent amblyopia in infants and children

This is particularly important in galactosemia and other pediatric metabolic cataracts.

A visually obstructing cataract in early childhood is an ophthalmic urgency because it can cause irreversible deprivation amblyopia.

Management involves:

Timely surgery when the visual axis is blocked
Accurate aphakic or pseudophakic optical correction
Occlusion therapy for amblyopia where indicated
Frequent assessment of fixation and visual development

4. Plan cataract surgery carefully

Before surgery:

Stabilize systemic disease as far as practical.
Evaluate cornea, retina, optic nerve, and macula.
Counsel regarding visual prognosis.
In diabetes, evaluate retinopathy and macular edema carefully.
In children, plan postoperative visual rehabilitation before operating.

Surgery is generally phacoemulsification with posterior chamber IOL implantation in adults. Pediatric surgery may involve lens aspiration with posterior capsulotomy and anterior vitrectomy in appropriate age groups, followed by contact lens, spectacle, or IOL-based rehabilitation.

Summary Table

Disorder	Main mechanism	Typical cataract appearance	Key systemic clues	Primary management
Diabetes mellitus	Sorbitol accumulation, osmotic lens swelling, oxidative stress	Snowflake cortical cataract, cortical vacuoles, early cataract	Hyperglycemia, polyuria, polydipsia, retinopathy	Glycemic control, retinal evaluation, cataract surgery if significant
Galactosemia	Galactitol accumulation with osmotic lens-fiber swelling	Oil-droplet cataract, cortical vacuoles	Neonatal jaundice, vomiting, liver dysfunction, failure to thrive	Immediate lactose/galactose restriction; early surgery if visual axis is blocked
Galactokinase deficiency	Galactitol accumulation	Cataract may be isolated	Often minimal systemic disease	Galactose restriction, observe or operate if visually significant
Hypocalcemia/hypoparathyroidism	Disturbed lens metabolism and protein stability	Small white iridescent cortical opacities	Tetany, cramps, paresthesias, seizures, post-thyroidectomy history	Correct calcium and endocrine disorder; surgery for established visual cataract
Wilson disease	Copper deposition	Sunflower cataract	Liver disease, neurologic/psychiatric signs, Kayser-Fleischer ring	Chelation or zinc therapy; surgery rarely needed
Fabry disease	Glycosphingolipid deposition	Wedge- or spoke-shaped posterior cataract	Acroparesthesias, angiokeratoma, renal/cardiac disease, cornea verticillata	Metabolic specialist treatment; operate only if visually significant
Myotonic dystrophy	Systemic genetic disorder affecting lens proteins	Christmas-tree cataract	Myotonia, muscle weakness, cardiac conduction disorder	Systemic evaluation and cataract surgery if required

Key Examination Points

Diabetes: snowflake cortical cataract due to sorbitol accumulation.
Galactosemia: oil-droplet cataract due to galactitol accumulation.
Galactose restriction should begin immediately when galactosemia is suspected, before confirmatory results return.
Hypocalcemia: small, white, iridescent cortical opacities, usually with tetany.
Wilson disease: sunflower cataract from copper deposition, usually not visually significant and may regress with chelation.
Fabry disease: posterior wedge- or spoke-shaped cataract.
In infants, management of the systemic condition and prevention of deprivation amblyopia are equally important.
Dense or visually significant established metabolic cataract is treated by cataract extraction with appropriate visual rehabilitation.

Short note on phacodonesis

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Phacodonesis

Phacodonesis is abnormal trembling or wobbling of the crystalline lens caused by weakness, stretching, or partial disruption of the zonular fibers that suspend the lens.

It is an early sign of lens subluxation. Kanski describes it as a tremulous lens seen on slit-lamp examination when the eye rapidly returns to the primary position. Kanski's Clinical Ophthalmology, 10th ed.

Clinical features

Visible oscillation of the lens with eye movement, especially after rapid horizontal saccades
May be associated with iridodonesis, which is tremulous movement of the iris
Asymmetry of anterior chamber depth
Lens edge may become visible through a dilated pupil if subluxation is advanced
Change in refraction, often increasing astigmatism or myopia
Monocular diplopia or blurred vision
Cataract formation due to abnormal lens support
In advanced cases: pupillary block, secondary angle-closure glaucoma, vitreous prolapse, or complete lens dislocation

Causes

Trauma - blunt trauma is a common cause of zonular rupture.
Pseudoexfoliation syndrome - a very common cause of acquired zonular weakness in older persons.
High myopia.
Hypermature cataract.
Previous intraocular surgery, including vitreoretinal surgery.
Hereditary connective-tissue disorders, especially:
- Marfan syndrome
- Homocystinuria
- Weill-Marchesani syndrome
- Ehlers-Danlos syndrome
Uveitis and chronic intraocular inflammation.
Idiopathic zonular weakness.

Examination

Phacodonesis is best elicited on slit-lamp examination by asking the patient to look rapidly from side to side and then back to primary gaze. The lens is observed for wobbling. Look carefully for:

Pseudoexfoliative material at the pupil margin or anterior lens capsule
Poor pupil dilatation
Iridodonesis
Visible lens equator
Capsular fibrosis or phimosis
Signs of previous trauma
Raised intraocular pressure
Retinal pathology or lens displacement on dilated examination

The Wills Eye Manual advises observing the lens during back-and-forth saccadic movements and evaluating for pseudoexfoliation and signs of remote or acute ocular trauma. The Wills Eye Manual, Lens Subluxation work-up section.

Significance in Cataract Surgery

Phacodonesis is a warning sign of zonular instability. It increases the risk of:

Difficulty in capsulorhexis
Extension of capsular tear
Zonular dialysis
Posterior capsular rupture
Vitreous loss
Dropped nucleus
Intraocular lens decentration or late in-the-bag IOL dislocation

Therefore, it must be identified during preoperative assessment.

Management

1. Mild phacodonesis without visual impairment

Observe periodically.
Treat associated disease, such as pseudoexfoliation-related glaucoma or uveitis.
Counsel the patient regarding the risk of progressive lens subluxation.

2. Cataract surgery in an eye with phacodonesis

Surgery should be planned as a complex cataract procedure.

Important measures include:

Good pupil dilatation, with iris hooks or a pupil expansion ring if required
Gentle capsulorhexis with minimal stress on zonules
Use of capsular hooks or retractors for focal zonular weakness
Use of a capsular tension ring (CTR) in mild to moderate diffuse zonular weakness
Use of a scleral-fixated modified CTR or capsular tension segment when zonular loss is more extensive
Low-flow, low-vacuum phacoemulsification settings
Minimal rotation and manipulation of the nucleus
Avoidance of excessive capsular-bag movement
In-the-bag IOL placement if adequate capsular support remains

3. Severe subluxation or inadequate capsular support

If the capsular bag cannot safely support an IOL, options include:

Removal of the lens with anterior vitrectomy when required
Scleral-fixated posterior chamber IOL
Iris-fixated IOL
Anterior chamber IOL in carefully selected cases
Leaving the patient aphakic temporarily in complex situations

Key point

Phacodonesis indicates zonular weakness until proven otherwise. Its recognition before cataract surgery permits appropriate planning, use of capsular-support devices, and prevention of serious intraoperative complications.

A recent evidence search did not identify a directly relevant systematic review in the last two years.

Short note on factors affecting astigmatism in cataract surgery and post operative astigmatism

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Factors Affecting Astigmatism in Cataract Surgery and Postoperative Astigmatism

Definition

Postoperative astigmatism is the refractive astigmatism present after cataract surgery. It results from the vector combination of:

Pre-existing corneal astigmatism
Posterior corneal astigmatism
Surgically induced astigmatism (SIA)
Residual astigmatism due to toric IOL error, rotation, tilt, or decentration

It may cause blurred vision, ghost images, glare, reduced unaided visual acuity, and poor satisfaction, especially after multifocal or EDOF IOL implantation.

Factors Affecting Astigmatism in Cataract Surgery

1. Pre-existing corneal astigmatism

This is the most important preoperative factor.

It may be with-the-rule: vertical meridian is steeper.
It may be against-the-rule: horizontal meridian is steeper.
It may be oblique.
It may be regular or irregular.

Regular astigmatism can generally be managed by incision planning, arcuate incisions, or a toric IOL. Irregular astigmatism due to keratoconus, corneal scar, dry eye, or previous corneal surgery needs further assessment before planning toric correction.

2. Posterior corneal astigmatism

Total corneal astigmatism is determined by both anterior and posterior corneal surfaces. Measuring anterior keratometry alone can produce error in toric IOL planning.

Modern toric calculators should incorporate:

Posterior corneal astigmatism
Estimated effective lens position
Surgically induced astigmatism
IOL spherical power

The ESCRS recommends corneal topography or tomography before toric IOL implantation and use of methods that account for posterior corneal astigmatism and effective lens position. ESCRS recommendations

3. Ocular surface and keratometry accuracy

Dry eye disease, blepharitis, meibomian gland dysfunction, epithelial irregularity, contact lens wear, and poor tear film can produce unstable keratometry.

This may cause:

Incorrect estimation of astigmatic magnitude
Incorrect axis measurement
Wrong toric IOL selection
Residual postoperative cylinder

The ocular surface should therefore be treated and corneal measurements repeated once stable.

4. Size of incision

Larger incisions induce more astigmatism because they weaken and flatten the corneal meridian in which they are made.

Phacoemulsification through a small clear corneal incision usually induces little astigmatism.
SICS induces more astigmatism than micro-incision phaco because its incision is larger.
Conventional ECCE, especially when sutured, may induce considerable astigmatism.

Kanski notes that suturing of a cataract incision can induce substantial corneal astigmatism. Kanski's Clinical Ophthalmology, 10th ed., Manual cataract surgery section.

5. Site and axis of incision

A corneal incision flattens the meridian on which it is placed.

A superior incision may induce or increase against-the-rule astigmatism.
A temporal incision usually has less astigmatic effect because it is farther from the visual axis.
Placing an incision on the steep meridian can reduce mild pre-existing regular astigmatism.
Incorrect incision placement can increase existing astigmatism or rotate its axis.

6. Incision architecture

Surgically induced astigmatism varies with:

Length of the incision
Width and shape of incision
Corneal versus sclero-corneal location
Single-plane, two-plane, or three-plane construction
Tunnel length
Wound hydration
Thermal damage or wound burn
Wound leak or poor apposition

A poorly constructed wound can cause unpredictable corneal flattening and variable postoperative astigmatism.

7. Sutures

Sutures can produce considerable astigmatism.

Factors include:

Number of sutures
Tightness of suture
Unequal tension
Suture placement
Suture loosening or breakage
Timing and sequence of suture removal

A tight suture steepens the meridian in which it lies. Selective suture removal can be used to reduce postoperative astigmatism after large-incision surgery.

8. Surgeon-related surgically induced astigmatism

Surgically induced astigmatism (SIA) is the change in corneal astigmatism produced by the operation itself. It is not a fixed scalar value because astigmatism has both magnitude and axis.

SIA differs between surgeons because of differences in:

Incision size
Site of incision
Architecture
Surgical technique
Wound hydration
Frequency of suturing
Complications

For accurate toric IOL planning, the surgeon should calculate and use a personal SIA value derived from stable postoperative outcomes.

9. IOL-related factors

Toric IOL outcomes depend on:

Correct cylinder power selection
Correct calculation of intended axis
Accurate intraoperative axis marking
Precise IOL alignment
Complete removal of viscoelastic behind the IOL
Stable capsular bag and zonular support
Absence of postoperative IOL rotation

Each degree of toric IOL rotation reduces its effective cylindrical correction by approximately 3.3%. At 30 degrees of rotation, the intended astigmatic correction is effectively lost.

10. Capsular bag and zonular stability

Pseudoexfoliation, trauma, high myopia, phacodonesis, zonular dialysis, capsular contraction, and improper IOL placement can lead to IOL tilt, decentration, or toric IOL rotation. This may produce residual astigmatism or other optical aberrations.

Causes of Postoperative Astigmatism

A. Pre-existing residual astigmatism

Inadequately treated corneal astigmatism
Wrong preoperative keratometry
Unrecognized irregular astigmatism
Failure to account for posterior corneal astigmatism

B. Surgically induced astigmatism

Large incision
Incision placed away from the planned axis
Excessive wound manipulation
Poor wound architecture
Wound burn
Sutures, especially tight or uneven sutures
Wound leak or delayed healing

C. Toric-IOL-related astigmatism

Incorrect IOL cylinder power
Incorrect IOL axis calculation
Incorrect preoperative marking due to cyclotorsion
Misalignment during implantation
Postoperative IOL rotation
IOL tilt or decentration
Inaccurate estimation of surgeon SIA

D. Corneal causes

Persistent corneal edema
Dry eye disease
Epithelial irregularity
Corneal scar
Infection
Descemet membrane detachment
Pterygium
Keratoconus or corneal ectasia

Prevention of Postoperative Astigmatism

Treat ocular surface disease before final keratometry.
Confirm repeatable keratometry with appropriate instruments.
Use corneal topography or tomography when astigmatism is significant or irregular.
Calculate total corneal astigmatism, including posterior corneal effect.
Use a small, well-constructed, reproducible incision.
Choose incision site according to pre-existing astigmatism where appropriate.
Use the surgeon's own SIA in toric IOL calculations.
Implant and accurately align a toric IOL in eyes with significant regular corneal astigmatism.
Ensure adequate capsular support and remove viscoelastic from behind a toric IOL.
Avoid unnecessary sutures; if used, ensure symmetric tension and manage removal appropriately.

For regular corneal astigmatism, toric IOLs are generally the most predictable correction method. ESCRS recommends considering them from 1.0 D of corneal astigmatism, with stronger evidence when astigmatism exceeds 2.0 D. ESCRS guideline

Management of Postoperative Astigmatism

Cause or situation	Management
Mild, stable residual cylinder	Spectacles or contact lenses
Dry eye or irregular tear film	Ocular surface treatment, then repeat refraction
Tight or uneven sutures	Selective suture removal after wound healing
Significant early toric IOL rotation	Early surgical realignment of toric IOL
Stable regular residual astigmatism	Corneal arcuate incision, limbal relaxing incision, or laser refractive enhancement in selected eyes
Large residual spherical or cylindrical error	IOL exchange, piggyback IOL, or corneal laser enhancement depending on cause and timing
Irregular astigmatism	Treat underlying corneal disorder; rigid gas-permeable or scleral contact lens may be needed

Key point

Postoperative astigmatism is minimized by accurate assessment of total corneal astigmatism, a small and properly placed incision, calculation of surgeon-specific SIA, and accurate toric IOL planning and alignment.

A recent systematic review found that incision site affects surgically induced astigmatism in manual small-incision cataract surgery (PMID: 41530563).

Note on causes, presentation and management of PCO of lens

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Posterior Capsule Opacification (PCO)

Definition

Posterior capsule opacification (PCO) is clouding of the posterior lens capsule following extracapsular cataract extraction or phacoemulsification with posterior chamber intraocular lens (IOL) implantation. It is commonly called a secondary cataract, though it is not a true recurrent cataract because the natural lens has been removed.

It is the most frequent late complication of cataract surgery.

PCO occurs because residual lens epithelial cells remain in the capsular bag after surgery. These cells proliferate, migrate over the posterior capsule, and undergo fibrous transformation, causing loss of capsular transparency.

Pathogenesis and Causes

During cataract surgery, the central anterior capsule and lens material are removed, but some lens epithelial cells (LECs) remain, especially at the equator of the capsular bag.

These residual cells can:

Proliferate
Migrate posteriorly over the posterior capsule
Transform into myofibroblast-like cells
Produce collagen and extracellular matrix
Cause wrinkling, fibrosis, and clouding of the capsule

Types of PCO

1. Fibrotic PCO

Caused by migration and fibrous transformation of lens epithelial cells.
Produces a white, fibrotic, wrinkled posterior capsule.
May cause capsular contraction and IOL decentration in severe cases.
More common in eyes with inflammation or pseudoexfoliation.

2. Regenerative PCO or Elschnig pearl PCO

Caused by proliferation of equatorial lens epithelial cells.
Cells form clusters of translucent, round, pearl-like structures called Elschnig pearls.
These may migrate into the visual axis and reduce vision.

3. Soemmering ring

Peripheral circumferential proliferation of retained cortical material and lens epithelial cells between the anterior and posterior capsules.
Usually does not affect vision unless it becomes large, dislocates, or causes inflammation.

Risk Factors for PCO

Patient-related factors

Young age, particularly children and young adults
Uveitis or chronic intraocular inflammation
Diabetes mellitus
Retinitis pigmentosa
High myopia
Trauma
Myotonic dystrophy
Previous retinal surgery
Inadequate control of postoperative inflammation

PCO develops more rapidly in children because lens epithelial cells have a greater proliferative capacity. In pediatric cataract surgery, posterior capsulotomy with anterior vitrectomy is often performed primarily to prevent visual-axis opacification.

Surgical factors

Retained cortical matter or lens epithelial cells
Incomplete cortical clean-up
Inadequate polishing of the anterior capsule
Large capsulorhexis with inadequate overlap of the IOL optic
IOL placed outside the capsular bag
Posterior capsular rupture or complicated surgery
Postoperative inflammation

IOL-related factors

The frequency of PCO is influenced by IOL material and design.

PCO is reduced by:

In-the-bag IOL fixation
Good overlap of the IOL optic by the anterior capsulorhexis
A square, sharp posterior optic edge
Modern hydrophobic acrylic IOLs, which generally provide a better barrier to lens epithelial cell migration than older round-edged designs

A sharp posterior optic edge produces a capsular bend that acts as a mechanical barrier to migration of lens epithelial cells.

Clinical Presentation

PCO usually develops months to years after cataract surgery. It may occur earlier in children, young adults, and eyes with inflammation.

Symptoms

The presentation resembles recurrence of cataract:

Gradual, painless deterioration of vision after an initially successful cataract operation
Blurring or haziness of vision
Glare, especially while driving at night
Halos around lights
Reduced contrast sensitivity
Difficulty reading
Monocular diplopia or ghost images
Poor quality of vision despite a clear cornea and well-positioned IOL

A patient may have relatively preserved Snellen acuity but significant glare or reduced contrast. The AAO guidance on Nd:YAG capsulotomy notes that glare testing can help confirm functional impairment when PCO seems mild on examination.

Signs on slit-lamp examination

Loss of red reflex
Hazy or opaque posterior capsule behind an IOL
Fine folds or wrinkles in the posterior capsule
Fibrosis and contraction of the capsule
Pearl-like, grape-like clusters of Elschnig pearls
Peripheral Soemmering ring
Reduced fundus view in dense PCO

Differential Diagnosis of Reduced Vision After Cataract Surgery

Before diagnosing PCO, other causes of reduced vision should be excluded:

Uncorrected residual refractive error
Dry eye disease
Corneal edema or corneal decompensation
Cystoid macular edema
Diabetic macular edema
Age-related macular degeneration
Epiretinal membrane
Retinal detachment
Glaucoma
IOL decentration, tilt, or opacification
Posterior capsular phimosis
Chronic postoperative endophthalmitis

PCO should be treated only when it explains the patient's loss of visual acuity or visual function.

Management

1. Observation

No treatment is required when PCO is:

Mild
Peripheral
Not affecting vision, glare, or daily activities
Not obstructing retinal examination or treatment

The patient should be reviewed periodically.

2. Nd:YAG Laser Posterior Capsulotomy

Nd:YAG laser posterior capsulotomy is the standard treatment for visually significant PCO in cooperative older children and adults.

The laser creates a central opening in the posterior capsule, restoring a clear visual axis without entering the eye surgically.

Indications

Decreased visual acuity attributable to PCO
Functionally important glare or impaired contrast sensitivity
Difficulty in fundus examination or treatment of retinal disease due to PCO
Significant visual-axis obscuration

Technique: general principles

Dilate the pupil where appropriate.
Check IOP before treatment.
Use a focusing contact lens if required.
Focus laser pulses slightly posterior to the capsule to reduce IOL pitting.
Create a central opening large enough for the visual axis and, ideally, larger than the scotopic pupil to reduce glare and monocular diplopia.
Use the lowest effective energy and minimal number of shots.

A properly sized capsulotomy is important. A very small opening may produce glare, visual disturbance, or recurrent symptoms.

Advantages

Outpatient procedure
Non-incisional
Rapid improvement in vision in most cases
No sutures
Usually permanent treatment

A review of PCO management identifies Nd:YAG laser capsulotomy as the accepted treatment for PCO in older children and adults. PCO review

Complications of Nd:YAG Capsulotomy

Although generally safe, complications can occur:

Transient rise in intraocular pressure
Inflammation or anterior uveitis
IOL pitting or damage
Cystoid macular edema
Retinal tear or retinal detachment, particularly in predisposed eyes
Vitreous prolapse or disturbance
IOL movement or decentration
Macular hole, rarely
Recurrence or reclosure of the capsulotomy opening, especially in children
Rarely, activation of chronic low-grade endophthalmitis

Post-laser care

Check IOP after the procedure, particularly in glaucoma or high-risk patients.
Topical IOP-lowering medication may be used when indicated.
A short course of topical corticosteroid or NSAID may be prescribed according to clinical practice and inflammatory risk.
Advise the patient to return urgently for flashes, floaters, curtain-like visual loss, severe pain, or sudden reduction in vision.

Surgical Capsulotomy

Surgical posterior capsulotomy is rarely required in adults but may be needed when:

The patient cannot cooperate for laser treatment
PCO is very dense or fibrotic
There is associated vitreoretinal pathology requiring surgery
The patient is an infant or young child

In children

Children have a high risk of rapid visual-axis opacification. Therefore, during pediatric cataract extraction, surgeons often perform:

Primary posterior capsulotomy
Anterior vitrectomy

This is done to prevent early PCO and deprivation amblyopia. If visual-axis opacification occurs later, management may require surgical membranectomy with vitrectomy, especially in young children.

Prevention of PCO

PCO cannot be completely eliminated, but its incidence can be reduced by:

Thorough cortical clean-up during cataract surgery
In-the-bag IOL implantation
A well-centered continuous curvilinear capsulorhexis overlapping the IOL optic
Use of a square-edged posterior optic design
Use of modern hydrophobic acrylic IOLs where appropriate
Good control of postoperative inflammation
Primary posterior capsulotomy with anterior vitrectomy in selected pediatric cases

Summary

Aspect	Key point
Definition	Opacification of the posterior capsule after cataract surgery
Common name	Secondary cataract
Cause	Proliferation, migration, and fibrous transformation of residual lens epithelial cells
Main types	Fibrotic PCO, Elschnig pearl PCO, Soemmering ring
Symptoms	Gradual painless visual blurring, glare, halos, reduced contrast
Main sign	Hazy posterior capsule behind a well-positioned IOL
Standard treatment	Nd:YAG laser posterior capsulotomy
Pediatric management	Often primary posterior capsulotomy with anterior vitrectomy; surgical treatment if visual axis is obscured
Important complications of YAG	IOP rise, IOL pitting, uveitis, cystoid macular edema, retinal detachment

Key point: PCO is a common late consequence of cataract surgery due to residual lens epithelial cell proliferation. Once it produces functional visual impairment, Nd:YAG laser posterior capsulotomy is the usual effective treatment.

Note on fluid dynamics of phaco

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Fluid Dynamics of Phacoemulsification

Introduction

Phaco fluidics refers to the control of fluid inflow and outflow during phacoemulsification to maintain a stable anterior chamber while lens material is held, emulsified, and aspirated.

A stable chamber is necessary to protect:

Corneal endothelium
Iris
Posterior capsule
Zonules
Anterior vitreous face

The basic fluidic principle is:

Inflow of balanced salt solution into the eye must adequately compensate for fluid aspirated from the eye and fluid lost through the incision.

Components of Phaco Fluidics

1. Irrigation or infusion

Irrigation is the entry of balanced salt solution into the anterior chamber through the irrigation sleeve surrounding the phaco tip.

Functions

Maintains anterior chamber depth
Maintains intraocular pressure
Prevents collapse of the capsular bag
Maintains space between the phaco tip and posterior capsule
Cools the phaco needle during ultrasound delivery
Washes lens fragments toward the aspiration port

Sources of infusion pressure

A. Gravity fluidics

The infusion bottle is raised above the patient's eye. The height of the bottle creates hydrostatic pressure.

[ \text{Infusion pressure} \propto \text{height of bottle above the eye} ]

Increasing bottle height increases intraocular infusion pressure and improves chamber maintenance, but excessive pressure can cause high intraoperative IOP, corneal edema, and patient discomfort.

B. Active fluidics

Modern machines may use pressurized or active infusion systems rather than relying solely on bottle height. The machine aims to maintain a selected target IOP by automatically altering infusion pressure as aspiration demand changes.

Advantages include:

More stable anterior chamber
Reduced post-occlusion surge
Ability to work at lower target IOP
More consistent fluidics despite changing bottle volume or aspiration demand

2. Aspiration

Aspiration is removal of fluid, lens fragments, cortex, and viscoelastic from the eye through the aspiration port of the phaco needle.

It depends mainly on:

Aspiration flow rate
Vacuum
Pump type
Occlusion status of the phaco tip
Tubing compliance
Incision leakage
Infusion pressure

Important Fluidic Parameters

A. Aspiration flow rate (AFR)

Aspiration flow rate is the volume of fluid aspirated per unit time, usually expressed in mL/min or cc/min.

Role

AFR determines how rapidly lens material and fluid are drawn toward the phaco tip. It is responsible for followability.

Higher AFR: faster attraction of nuclear fragments to the tip
Lower AFR: slower attraction but greater control and safety

Thus, aspiration flow acts as a “third hand” by drawing fragments toward the phaco needle.

Clinical relevance

High flow is useful for:

Nuclear fragment removal
Efficient cortical aspiration
Good followability of mobile fragments

Low flow is preferred when working:

Near the posterior capsule
During epinucleus removal
With the last nuclear fragment
In shallow anterior chambers
In eyes with weak zonules or posterior capsule compromise

Excessive aspiration flow can cause anterior chamber instability, aspiration of iris, and increased risk of posterior capsular rupture.

B. Vacuum

Vacuum is the negative pressure generated in the aspiration line. It determines how strongly lens material is held at the phaco tip, also called holdability.

Functions

Holds the nuclear fragment against the tip
Allows impaling of the nucleus
Enables chopping maneuvers
Improves purchase on lens material
Helps remove cortex and epinucleus

Clinical relation

Parameter	Main function
Aspiration flow rate	Brings material toward the phaco tip: followability
Vacuum	Holds material at the phaco tip: holdability

High vacuum is valuable for phaco chop because the nucleus must be firmly held while the chopper divides it. However, high vacuum increases the risk of post-occlusion surge when occlusion breaks.

C. Vacuum rise time

Vacuum rise time is the speed at which the preset vacuum level is reached after occlusion of the aspiration port.

Fast rise time: rapid attainment of holding power
Slow rise time: more controlled vacuum generation

A rapid rise time is helpful in nuclear chopping, but may be less safe near the posterior capsule or with mobile fragments.

D. Intraocular pressure

Intraoperative IOP is determined by the balance between infusion pressure and outflow through aspiration and wound leakage.

Low IOP may lead to:

Shallow or collapsing anterior chamber
Posterior capsule movement toward the phaco tip
Iris prolapse
Corneal folds
Increased risk of posterior capsular rupture

Very high IOP may lead to:

Corneal edema
Pain in an awake patient
Reduced ocular perfusion pressure
Iris prolapse when instruments are withdrawn

The aim is a stable, adequately deep chamber at the lowest effective infusion pressure.

Types of Aspiration Pumps

1. Peristaltic pump

A peristaltic pump is a flow-based pump. Rotating rollers compress aspiration tubing and create forward fluid movement.

Characteristics

Aspiration flow rate is set directly.
Vacuum develops mainly when the tip becomes occluded.
Flow and vacuum can be adjusted relatively independently.
Provides controlled and predictable holdability after occlusion.

Advantages

Commonly used
Good control for nucleus chopping
Adjustable flow and vacuum
Relatively safe with appropriate settings

Limitation

When a fragment occluding the tip is suddenly aspirated, the built-up vacuum can cause a post-occlusion surge.

2. Venturi pump

A Venturi pump is a vacuum-based pump. It creates vacuum by compressed gas passing through a Venturi system.

Characteristics

Vacuum is present even without full tip occlusion.
Rapid vacuum rise and rapid response
Flow is generated secondary to pressure difference
Flow and vacuum cannot be independently controlled to the same degree as with a peristaltic pump

Advantages

Excellent followability
Rapid removal of fragments
Efficient for experienced surgeons

Limitations

Less forgiving
May produce greater chamber instability
Requires careful control near the posterior capsule and iris

Occlusion and Occlusion Break

Occlusion

Occlusion occurs when a lens fragment blocks the aspiration port.

In a peristaltic system:

The tip becomes blocked by lens material.
The pump continues to act on the tubing.
Negative pressure or vacuum rises.
The fragment is held firmly at the tip.

This is useful for chopping and emulsification.

Occlusion break

An occlusion break occurs when the fragment suddenly clears the aspiration port. The stored negative pressure in the aspiration tubing then causes a sudden rush of fluid from the anterior chamber into the aspiration line.

This is called post-occlusion surge.

Post-Occlusion Surge

Definition

Post-occlusion surge is sudden excessive aspiration of fluid from the anterior chamber immediately after a previously occluded phaco tip becomes unoccluded.

It can lead to sudden shallowing or collapse of the anterior chamber.

Mechanism

During tip occlusion, negative pressure builds in the aspiration tubing and the tubing may collapse. When the occluding lens fragment is suddenly aspirated:

The occlusion is released.
Collapsed tubing rapidly re-expands.
Stored vacuum pulls fluid quickly from the anterior chamber.
The anterior chamber becomes shallow.
The posterior capsule may move anteriorly toward the phaco tip.

Consequences

Posterior capsular rupture
Aspiration of posterior capsule
Zonular stress or dialysis
Iris aspiration
Corneal endothelial trauma
Anterior chamber collapse
Vitreous disturbance
Loss of nuclear fragments posteriorly in severe cases

Factors Increasing Surge

High vacuum setting
High aspiration flow rate
Low bottle height or inadequate infusion
Compliant, collapsible aspiration tubing
Large-bore aspiration tubing
Small, unstable incision with excessive wound leakage
Sudden release of a large occluding nuclear fragment
Poorly functioning inflow system

Laboratory data show that the magnitude of surge increases with higher aspiration vacuum. Phaco-system comparison study

Prevention of Surge

Use the lowest vacuum and aspiration flow required for the step.
Lower vacuum and flow near the posterior capsule and during removal of the last fragment.
Increase infusion pressure or bottle height if the chamber is unstable.
Ensure adequate irrigation sleeve flow and avoid blockage of irrigation ports.
Use a well-constructed, non-leaking incision.
Use low-compliance tubing where available.
Use anti-surge or occlusion-break response systems.
Use active fluidics where available.
Maintain the phaco tip centrally and avoid working too close to the posterior capsule.
Reduce settings promptly when a capsular rupture or zonular weakness is suspected.

Fluidic Balance in Different Steps of Phacoemulsification

Surgical step	Desired fluidic characteristics
Capsulorhexis	Stable chamber, low turbulence, adequate infusion
Hydrodissection	Controlled injection without excessive pressure; avoid capsular block
Nucleus chopping	High vacuum for firm hold, moderate flow, stable chamber
Nuclear fragment removal	Moderate to high flow for followability, suitable vacuum for holdability
Epinucleus removal	Lower to moderate vacuum and flow; avoid capsule aspiration
Last nuclear fragment	Lower vacuum and flow; maintain good infusion and work centrally
Cortex aspiration	Controlled flow and vacuum; avoid traction on capsule and zonules
Viscoelastic removal	Adequate flow with stable chamber; avoid shallowing and IOL movement

Fluid Dynamics During Hydrodissection

Hydrodissection involves injection of balanced salt solution under the anterior capsule to separate the cortex from the capsule.

Purpose

Mobilizes the nucleus
Separates cortical fibers from the capsule
Facilitates nucleus rotation
Reduces zonular stress during phacoemulsification

Important precaution: capsular block syndrome

Excessive fluid injection behind the nucleus without allowing fluid egress can cause posterior pressure, forward displacement of the nucleus, posterior capsular rupture, or “capsular block.”

Prevention:

Inject a small controlled fluid wave.
Decompress the capsular bag by gently depressing the lens nucleus.
Ensure fluid escapes around the equator of the lens.
Avoid forceful hydrodissection in posterior polar cataract or suspected weak posterior capsule.

Role of the Irrigation Sleeve

The irrigation sleeve surrounds the phaco needle and has side ports through which infusion fluid enters the anterior chamber.

Its roles are:

Maintain chamber volume and IOP
Balance aspiration outflow
Cool the phaco needle
Prevent thermal injury at the corneal incision

If the sleeve is retracted, damaged, blocked, or inadequately positioned, irrigation may be insufficient. This may cause:

Wound burn
Chamber instability
Corneal incision distortion
Increased risk of thermal endothelial damage

Wound Burn

A wound burn occurs when the phaco needle becomes excessively hot at the incision. It is usually caused by inadequate fluid flow around the needle.

Causes

Tight incision around the sleeve
Obstruction of irrigation ports
Excessive ultrasound energy
Prolonged continuous ultrasound
High vacuum with complete occlusion and little cooling flow
Sleeve retraction or damage

Effects

Corneal stromal whitening
Incision contraction
Significant postoperative astigmatism
Wound leak
Poor visual recovery

Prevention is by ensuring free irrigation, suitable incision size, use of pulse or burst ultrasound modes where appropriate, and avoiding prolonged ultrasound during complete occlusion.

Active Fluidics

In gravity fluidics, infusion pressure gradually falls as the bottle empties and chamber pressure may vary with aspiration demand. Active-fluidics systems attempt to maintain a selected IOP by dynamically increasing or reducing infusion pressure.

Advantages

More stable anterior chamber
Lower frequency and magnitude of surge
More predictable IOP throughout surgery
Better maintenance of chamber depth during high vacuum
May improve efficiency in dense cataracts

A review found that active fluidics can improve anterior-chamber stability and reduce surge compared with gravity-based systems, though settings and surgical technique remain important. Active-fluidics review

Practical Principles for Safe Phaco Fluidics

Maintain inflow greater than or equal to outflow.
Use vacuum for holdability and flow for followability.
Increase vacuum only when a firm nuclear hold is needed.
Use lower settings near the posterior capsule.
Anticipate surge whenever an occluded tip is likely to clear.
Keep the phaco tip in the central safe zone.
Use stable wound construction and adequate irrigation.
Adapt settings to lens density, chamber depth, zonular status, pupil size, and surgical stage.
In shallow chambers, weak zonules, pseudoexfoliation, or posterior capsular compromise, use more conservative settings.
Do not rely on machine settings alone. Constant observation of anterior chamber depth, capsule movement, and fragment behavior is essential.

Summary

Irrigation maintains chamber depth, IOP, and needle cooling.
Aspiration flow rate determines how quickly material is attracted to the phaco tip, that is, followability.
Vacuum determines how firmly material is held at the tip, that is, holdability.
Peristaltic pumps are flow-based and develop high vacuum mainly after occlusion.
Venturi pumps are vacuum-based and generate vacuum even without occlusion.
Post-occlusion surge is the major fluidic hazard and can cause anterior chamber collapse and posterior capsular rupture.
Safe surgery requires a balance between inflow, aspiration flow, vacuum, incision leakage, and real-time chamber stability.

Micro spherophakia

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microspherophakia slit lamp image lens

This composite educational image illustrates clinical findings associated with Traboulsi Syndrome, a rare genetic disorder characterized by microspherophakia and ectopia lentis. Panels A-D display anterior segment and slit-lamp photography. The right eye (OD) shows anterior microspherical lens subluxation into the anterior chamber (A, B) accompanied by iris atrophy and glaukomflecken (small white subcapsular opacities). The left eye (OS) demonstrates sectorial iris atrophy (C) and posterior-inferior lens subluxation (D). Panels E and F provide fundus photographs of both eyes, revealing a tessellated fundus background and small, slightly pale optic discs with a low cup-to-disc ratio. Panel G presents Optical Coherence Tomography (OCT) of the optic nerve head, featuring a retinal nerve fiber layer (RNFL) thickness map and quantitative analysis table. The OCT data indicates globally reduced RNFL thickness (average 83µm bilaterally) and small disc areas (1.59-1.66 mm²). These visuals demonstrate the ocular manifestations of ASPH gene mutations, emphasizing the importance of monitoring for secondary glaucoma and retinal changes in patients with lens abnormalities.

Microspherophakia

Definition

Microspherophakia is a congenital lens anomaly in which the crystalline lens is abnormally small, spherical, and more anteriorly positioned than normal. Because the lens has increased anteroposterior thickness and curvature, it has increased refractive power and commonly causes lenticular myopia.

It is often bilateral and may occur as an isolated familial condition or with systemic syndromes.

Etiology and associations

Microspherophakia results from abnormal development of the zonules and lens. Weak or abnormally short zonules fail to maintain the normal flattened lens contour, so the lens becomes rounded.

It may be:

Isolated familial microspherophakia, often autosomal dominant
Associated with Weill-Marchesani syndrome
Associated with Marfan syndrome
Associated with ectopia lentis et pupillae
Associated with hyperlysinemia
Associated with congenital rubella
Rarely associated with Peters anomaly and other ocular developmental disorders

Kanski describes microspherophakia as a small, spherical lens that can occur in isolation or with Marfan and Weill-Marchesani syndromes, hyperlysinemia, congenital rubella, Peters anomaly, and ectopia lentis et pupillae. Kanski's Clinical Ophthalmology, 10th ed.

Weill-Marchesani syndrome

This is the classic systemic association. It is a connective-tissue disorder characterized by:

Short stature
Brachydactyly, short broad fingers
Joint stiffness
Microspherophakia
Lenticular myopia
Ectopia lentis
Secondary glaucoma
Occasionally cardiovascular abnormalities

GeneReviews on Weill-Marchesani syndrome identifies microspherophakia as its major ocular feature.

Clinical Features

Symptoms

Patients may present with:

Blurred distance vision due to high myopia
Sudden worsening of vision from lens subluxation
Intermittent colored halos, headache, and ocular pain due to angle closure
Acute painful red eye with nausea or vomiting in acute angle-closure glaucoma
Progressive loss of vision due to glaucoma or cataract

Ocular signs

Bilateral small, rounded, highly convex crystalline lens
Increased lens thickness and reduced equatorial diameter
High lenticular myopia
Shallow anterior chamber, particularly centrally
Narrow iridocorneal angle
Phacodonesis due to zonular weakness
Lens subluxation or complete lens dislocation
Visible lens equator after pharmacologic mydriasis
Iridodonesis in advanced zonular weakness
Raised intraocular pressure
Optic-disc cupping and glaucomatous field loss in longstanding disease

Important complications

Lenticular myopia
The increased curvature and power of the spherical lens cause marked myopia.
Pupillary block and angle-closure glaucoma
The anteriorly placed spherical lens causes relative pupillary block. Aqueous accumulates behind the iris, producing iris bombe and closure of the angle.
Reverse pupillary block
When the lens dislocates into the anterior chamber, it can obstruct aqueous flow differently and cause severe pressure elevation.
Lens subluxation or dislocation
Weak zonules may permit anterior, posterior, or inferior lens displacement.
Cataract formation
May occur due to chronic lens instability or metabolic disturbance within the lens.

Investigations

Visual acuity and cycloplegic refraction
Slit-lamp examination with dilation
Intraocular pressure measurement
Gonioscopy to assess angle width and peripheral anterior synechiae
Anterior-segment OCT or ultrasound biomicroscopy to demonstrate a small spherical lens, shallow anterior chamber, and lens position
Optic-disc examination, OCT retinal nerve fiber layer analysis, and visual fields for glaucoma assessment
Systemic examination for short stature, brachydactyly, joint stiffness, and cardiovascular abnormalities
Genetic consultation where a syndromic cause is suspected

Management

Management depends on refractive error, degree of lens displacement, angle status, and glaucoma.

1. Optical correction and observation

Appropriate when there is no glaucoma or visually significant subluxation.

Correct myopia with spectacles or contact lenses.
Regularly monitor visual acuity, refraction, IOP, angle status, optic nerve, and lens position.
Educate the patient about symptoms of acute angle closure.

2. Management of pupillary block and glaucoma

Medical treatment in acute angle closure

Initial treatment includes lowering IOP with appropriate topical and systemic antiglaucoma therapy and controlling inflammation. The patient needs urgent ophthalmic assessment.

Avoid miotics in microspherophakia, particularly with a very anterior lens or lens subluxation, because pupillary constriction may worsen pupillary block and forward lens movement.

Laser peripheral iridotomy

Laser peripheral iridotomy may relieve a component of relative pupillary block, but it may not be sufficient if the spherical lens remains markedly anterior or mobile. It does not correct the underlying lens abnormality.

Lens extraction

Lens extraction is often the definitive treatment when the lens is causing pupillary block, persistent angle closure, uncontrolled IOP, or visually significant refractive error/cataract.

3. Lens surgery

Indications for lensectomy or cataract extraction include:

Recurrent or uncontrolled angle-closure glaucoma
Lens-induced pupillary block
Progressive lens subluxation or dislocation
Significant cataract
Marked refractive error not adequately correctable optically
Intolerable anisometropia

Surgical challenges

Surgery is technically difficult because of:

Weak zonules and phacodonesis
Small capsular bag
Lens mobility
Shallow anterior chamber
Risk of vitreous loss
Risk of postoperative IOL decentration

Possible approaches include:

Lens aspiration or phacoemulsification with careful low-fluidic settings
Capsular hooks or capsule-retracting devices for zonular support
Capsular tension ring or a scleral-fixated capsular tension device when suitable
Anterior vitrectomy if required
Scleral-fixated IOL, iris-fixated IOL, or delayed secondary IOL when capsular support is inadequate

In children, the choice between aphakic correction and primary IOL implantation is individualized and must include amblyopia prevention.

4. Long-term glaucoma follow-up

Even after lens removal, glaucoma surveillance must continue because:

Peripheral anterior synechiae may persist
Trabecular damage may have occurred before treatment
Some patients require ongoing topical medication or glaucoma surgery

Summary

Feature	Microspherophakia
Lens morphology	Small, spherical, thick, highly convex lens
Main refractive effect	High lenticular myopia
Key mechanism	Weak or abnormal zonules fail to flatten the lens
Major association	Weill-Marchesani syndrome
Major complications	Pupillary block, angle-closure glaucoma, lens subluxation/dislocation, cataract
Diagnosis	Slit-lamp examination, gonioscopy, IOP, anterior-segment imaging
Conservative care	Spectacles/contact lenses and close monitoring
Definitive treatment when complicated	Lens extraction or lensectomy with appropriate capsular/IOL support
Important caution	Laser iridotomy may help pupillary block but may not eliminate the lens-related mechanism

Management of cataract with uvietis

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Management of Cataract with Uveitis

Cataract in uveitis may result from chronic intraocular inflammation, recurrent attacks of anterior uveitis, or long-term corticosteroid therapy. It is frequently posterior subcapsular and may be associated with posterior synechiae, small pupil, band keratopathy, glaucoma, cystoid macular edema (CME), hypotony, and macular or optic nerve disease.

The aim is not simply cataract removal. Successful management depends on controlling inflammation before surgery, careful perioperative anti-inflammatory treatment, atraumatic surgery, suitable IOL selection, and close postoperative surveillance.

Indications for Surgery

Cataract surgery is considered when there is:

Visual disability due to cataract
Cataract preventing examination or treatment of the retina, choroid, or optic nerve
Lens-induced inflammation, such as phacoantigenic uveitis
Cataract interfering with treatment of posterior-segment disease
Severe anisometropia or amblyopia risk in children

Visual prognosis must be discussed carefully because postoperative visual acuity may be limited by:

Cystoid macular edema
Epiretinal membrane
Macular scar or chorioretinal atrophy
Optic atrophy
Glaucomatous damage
Retinal detachment
Corneal opacity or band keratopathy

1. Preoperative Management

A. Achieve quiescent uveitis

The cardinal rule is:

Elective cataract surgery should be performed only after uveitis has been inactive for at least 3 months.

This means no anterior chamber cells, flare increase, active vitritis, retinal vasculitis, or active chorioretinal inflammation for a sustained period.

Kanski states that chronic uveitis should ideally be controlled for a minimum of 3 months before cataract surgery. Kanski's Clinical Ophthalmology, 10th ed., Surgery section.

Eyes with active inflammation at or shortly before surgery have a higher risk of:

Severe postoperative inflammation
Fibrinous anterior chamber reaction
Posterior synechiae
Cystoid macular edema
Posterior capsule opacification
IOL deposits and membrane formation
Hypotony or secondary glaucoma
Poor visual outcome

A review similarly supports at least three months of quiescence before surgery. Perioperative uveitic-cataract review

Exceptions

Urgent surgery may be needed despite active inflammation in uncommon situations, such as:

Lens-induced uveitis
Uncontrolled lens-induced glaucoma
Intumescent cataract causing phacomorphic angle closure
Cataract preventing essential evaluation or treatment of a sight-threatening posterior-segment condition

In such cases, inflammation should still be aggressively controlled before, during, and after surgery.

B. Identify the cause and type of uveitis

Determine whether uveitis is:

Anterior, intermediate, posterior, or panuveitis
Infectious or noninfectious
Unilateral or bilateral
Acute, recurrent, or chronic
Associated with a systemic disease

Important causes include:

HLA-B27-associated uveitis
Juvenile idiopathic arthritis-associated uveitis
Sarcoidosis
Tuberculosis
Syphilis
Toxoplasmosis
Viral anterior uveitis
Behçet disease
Vogt-Koyanagi-Harada disease
Fuchs uveitis syndrome
Sympathetic ophthalmia

Infectious uveitis must be treated specifically before elective cataract surgery. Systemic immunosuppression should not be increased without excluding or adequately treating infection.

C. Preoperative evaluation

The following should be documented:

Ocular examination

Best-corrected visual acuity and refraction
Intraocular pressure
Degree of anterior chamber cells and flare
Keratic precipitates
Posterior synechiae and pupillary membrane
Pupil size and dilatation
Cataract morphology and density
Zonular status
Corneal status, including band keratopathy
Fundus examination where possible

Posterior-segment assessment

Macular OCT to detect CME, epiretinal membrane, or macular atrophy
B-scan ultrasonography if the fundus cannot be viewed
Fundus fluorescein angiography if retinal vasculitis or macular leakage is suspected
Optic nerve evaluation
Visual field and OCT retinal nerve fiber layer assessment when glaucoma is present

Biometry

Perform IOL power calculation after ocular surface and inflammation are stable.
In children or eyes with posterior synechiae, measurements may be difficult.
Explain that final refractive accuracy may be limited in complex eyes.

D. Control associated ocular problems before surgery

Problem	Management before surgery
Active uveitis	Topical, periocular, systemic corticosteroid, immunomodulatory therapy, or disease-specific treatment
Infectious uveitis	Appropriate antimicrobial treatment with uveitis specialist input
Cystoid macular edema	Control inflammation, topical NSAID/steroid, periocular or intravitreal therapy when indicated
Raised IOP or glaucoma	Optimize topical therapy, avoid pro-inflammatory drugs where possible, plan combined surgery selectively
Band keratopathy	Consider EDTA chelation if it significantly impairs view or vision
Posterior synechiae	Plan synechiolysis and pupil expansion during surgery
Poor pupillary dilatation	Plan iris hooks or pupil expansion ring
Hypotony	Identify and manage active ciliary-body inflammation before surgery

2. Perioperative Control of Inflammation

Corticosteroid prophylaxis

The steroid regimen is individualized based on severity, location, and history of uveitis.

Possible approaches include:

Increased frequency of topical corticosteroid before surgery
Periocular corticosteroid injection
Intravitreal corticosteroid in selected cases
Short course of oral corticosteroid in moderate or high-risk noninfectious uveitis
Continuation or adjustment of existing immunomodulatory therapy

The purpose is to suppress the surgical inflammatory response and reduce the risk of postoperative CME and recurrence.

General principles

Maintain systemic immunomodulatory therapy where appropriate.
Avoid abrupt withdrawal of systemic steroids or immunosuppressants.
Coordinate care with a uveitis specialist, rheumatologist, or physician managing systemic disease.
Use prophylactic topical NSAIDs in many cases, particularly if CME risk is high, though exact regimens vary.

No single steroid regimen is universally correct. The chosen protocol depends on the specific uveitis diagnosis and individual risk of recurrence.

3. Intraoperative Management

A. Preferred surgical procedure

Small-incision phacoemulsification with in-the-bag posterior chamber IOL implantation is generally preferred when capsular support is adequate.

Principles are:

Small, secure, self-sealing incision
Minimal iris manipulation
Gentle capsulorhexis
Meticulous cortical cleanup
Preservation of capsular bag integrity
Stable in-the-bag IOL fixation
Removal of viscoelastic from behind the IOL

Excessive surgical manipulation increases postoperative inflammation.

B. Management of small pupil and posterior synechiae

Chronic uveitis commonly causes posterior synechiae and a poorly dilating pupil.

Techniques

Viscomydriasis with cohesive ophthalmic viscosurgical device
Gentle mechanical synechiolysis
Iris hooks
Pupil expansion ring
Careful pupillary membrane removal if necessary

Avoid unnecessary iris trauma because it can worsen postoperative inflammation, bleeding, iris atrophy, and CME.

C. Capsulorhexis and capsular bag care

A well-centered, moderately sized continuous curvilinear capsulorhexis is important because uveitic eyes are prone to:

Capsular fibrosis
Anterior capsular phimosis
Posterior capsule opacification
IOL decentration

A capsulorhexis that overlaps the IOL optic helps maintain long-term IOL centration and may reduce cell migration.

D. IOL selection

Preferred IOL

A single-piece or three-piece hydrophobic acrylic posterior chamber IOL placed in the capsular bag is commonly preferred.

Hydrophobic acrylic lenses are generally associated with good biocompatibility and lower posterior synechiae formation than some silicone lenses in uveitic eyes. Uveitic-cataract review

Avoid where possible

Anterior chamber IOLs
Iris-claw IOLs, unless no better option is feasible
Silicone IOLs, particularly in patients who may need vitreoretinal surgery with silicone oil
Multifocal IOLs in most uveitic eyes, because reduced contrast sensitivity, CME risk, retinal disease, and IOL deposits may compromise quality of vision

If capsular support is inadequate

Options are individualized:

Leave aphakic temporarily
Scleral-fixated posterior chamber IOL
Secondary IOL after inflammation is controlled

Anterior chamber IOLs are generally avoided because they may increase inflammation and risk of corneal or angle complications.

E. Primary posterior capsulotomy

In young children, primary posterior capsulotomy with anterior vitrectomy is often required to prevent visual-axis opacification. In adults, the posterior capsule is usually left intact and later PCO is treated by Nd:YAG capsulotomy once inflammation is well controlled.

4. Postoperative Management

Postoperative follow-up should be more frequent and prolonged than after routine cataract surgery.

A. Anti-inflammatory treatment

Typical treatment includes:

Intensive topical corticosteroid initially, followed by slow taper
Cycloplegic or mydriatic drops to reduce pain, prevent posterior synechiae, and stabilize the blood-aqueous barrier
Topical NSAID in selected patients to lower CME risk
Periocular, intravitreal, or systemic corticosteroids if inflammation is severe or recurrent
Continuation or adjustment of systemic immunomodulatory treatment as required

The steroid taper should be slower than in routine cataract surgery and based on anterior chamber reaction, IOP, macular status, and disease type.

B. Monitor actively for complications

Early complications

Severe anterior chamber inflammation
Fibrin membrane
Hyphema
IOP rise due to steroid response, inflammation, retained viscoelastic, or pre-existing glaucoma
Corneal edema
Wound leak
Early posterior synechiae
Acute infection, including endophthalmitis

Intermediate and late complications

Cystoid macular edema
Recurrent uveitis
Posterior capsule opacification
Anterior capsular phimosis
IOL deposits
IOL decentration
Glaucoma
Hypotony
Epiretinal membrane
Retinal detachment in predisposed eyes

5. Cystoid Macular Edema

CME is one of the most important causes of poor vision after cataract surgery in uveitic eyes.

Prevention

Operate only when uveitis is quiet
Use adequate perioperative corticosteroid therapy
Consider topical NSAID therapy
Identify and treat pre-existing macular edema before surgery
Minimize surgical manipulation

Management

Intensify topical corticosteroid and NSAID treatment
Treat active intraocular inflammation
Consider periocular corticosteroid, intravitreal corticosteroid, or systemic treatment in selected cases
Perform macular OCT to monitor response
Exclude other causes, such as diabetic macular edema, epiretinal membrane, or retinal vein occlusion

Special Situations

Juvenile idiopathic arthritis-associated uveitis

This group has a high risk of severe postoperative inflammation, hypotony, glaucoma, cyclitic membrane, CME, and amblyopia.

Surgery should be delayed until inflammation has been controlled for at least 3 months.
Multidisciplinary management is needed.
Long-term immunomodulatory therapy may be necessary.
Primary IOL implantation is individualized, particularly in young children.

The Wills Eye Manual notes the high complication rate of cataract surgery in JIA-associated uveitis and recommends waiting until the eye is inflammation-free for at least three months. The Wills Eye Manual, Uveitis treatment section.

Fuchs uveitis syndrome

Cataract surgery generally has a relatively favorable prognosis.
Mild chronic inflammation may be present.
Amsler sign, bleeding from angle vessels during paracentesis, may occur.
Glaucoma and vitreous opacities should be assessed.

Behçet disease, VKH, sarcoidosis, or posterior/panuveitis

Ensure complete control of posterior-segment inflammation.
Exclude active retinal vasculitis and macular edema.
Systemic immunosuppression may be required before and after surgery.
Visual outcome depends significantly on retinal and optic nerve status.

Summary: Practical Management Plan

Confirm that cataract is the major cause of visual loss.
Identify the uveitis type and rule out active infection.
Control inflammation for at least 3 months before elective surgery.
Assess macula with OCT and manage pre-existing CME.
Control glaucoma, ocular surface disease, and band keratopathy.
Give individualized perioperative anti-inflammatory prophylaxis.
Perform gentle small-incision phacoemulsification with minimal iris trauma.
Release synechiae and enlarge a small pupil using safe mechanical methods.
Implant a hydrophobic acrylic IOL in the capsular bag when possible.
Use intensive postoperative steroid therapy with slow taper and close follow-up.
Monitor for CME, recurrent uveitis, IOP elevation, PCO, and capsular contraction.

Key point: The strongest predictor of a favorable outcome in uveitic cataract surgery is a quiet eye with well-controlled inflammation before surgery, combined with meticulous surgery and sustained postoperative anti-inflammatory care.

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