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Cataract - A Complete Ophthalmological Review

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1. Definition and Epidemiology

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2. Anatomy of the Lens

• Zonules hold the lens in position, suspending it from the ciliary body.
• Capsule - an acellular membrane enclosing the lens material.
• Lens epithelium - cuboid cells beneath the anterior capsule extending to the equator; cells in the germinative zone divide continuously and differentiate into lens fibers.
• Lens substance - central nucleus surrounded by cortical material.

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3. Symptoms of Cataract

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4. Classification of Cataract

4A. Age-Related (Acquired) Cataract

i. Posterior Subcapsular (PSC) Cataract

• Located just in front of the posterior capsule
• Granular or plaque-like on oblique slit-lamp biomicroscopy
• Appears black and vacuolated on retroillumination; vacuoles are swollen migratory lens epithelial cells (bladder/Wedl cells)
• Due to location at the nodal point, has a particularly profound impact on vision even when small
• Characteristic symptoms: glare (especially from oncoming car headlights), worse in bright light (miosis) and on near tasks
• Associated with: corticosteroid use, diabetes, irradiation, uveitis

ii. Nuclear Sclerotic Cataract

• Exaggeration of the normal ageing change of the lens nucleus
• Associated with myopia due to increased refractive index - this can cause "second sight of the aged" where presbyopic patients can temporarily read without spectacles
• Characterized by a yellowish hue due to urochrome pigment deposition
• Best assessed with oblique slit-lamp beam
• Retroillumination shows good red reflex but a subtle distinction between nucleus and cortex
• In advanced stages: nucleus appears brown (brunescent) or in rare cases black (nigricans)

iii. Cortical Cataract

• May involve the anterior, posterior or equatorial cortex
• Starts as clefts and vacuoles between lens fibres due to cortical hydration
• Subsequent opacification forms cuneiform (wedge-shaped) or radial spoke-like opacities
• Often found initially in the inferonasal quadrant
• Glare is a prominent symptom

iv. Christmas Tree Cataract

• Uncommon; polychromatic needle-like formations in the deep cortex and nucleus
• Has a distinctive glittering multicolored appearance on slit-lamp examination

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4B. Maturity Stages of Cataract

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4C. Secondary (Complicated) Cataract

• Chronic anterior uveitis - the most common cause of secondary cataract. Incidence related to duration/intensity of inflammation. Earliest sign: polychromatic lustre at posterior pole. Progresses to posterior and anterior opacities. Topical/systemic steroids used in treatment are also causative.
• Acute congestive angle closure - causes small anterior grey-white subcapsular opacities called glaukomflecken - focal infarcts of lens epithelium; pathognomonic of previous acute angle closure
• High (pathological) myopia - posterior subcapsular opacity and early-onset nuclear sclerosis
• Hereditary fundus dystrophies - retinitis pigmentosa, Leber congenital amaurosis, gyrate atrophy, Stickler syndrome - usually posterior subcapsular opacity
• Secondary to medication - systemic and topical steroids cause posterior subcapsular cataracts
• Radiation, vitreoretinal surgery (silicone oil, gas tamponade), trauma

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4D. Cataract in Systemic Disease

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4E. Traumatic Cataract

• Blunt trauma - contrecoup forces cause lens fibre disruption; may cause rosette-shaped opacity at the posterior pole; stellate opacity at the anterior pole
• Perforating injury - lens rapidly opacifies (may swell, causing secondary glaucoma)
• Radiation - X-rays, neutrons, and infrared rays can cause posterior subcapsular cataract (glassblowers' cataract from chronic infrared exposure)
• Electrical - anterior subcapsular opacities following electric shock or lightning strike
• Chemical - acids/alkalis affecting the lens secondarily after corneal/anterior segment involvement

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4F. Congenital Cataract

Aetiology

• Galactosaemia - oil-droplet opacity; responds to early dietary galactose restriction
• Galactokinase deficiency - nuclear cataract
• Hypocalcaemia (hypoparathyroidism)
• Lowe (oculocerebrorenal) syndrome - dense cataract; X-linked recessive

• Rubella - bilateral dense nuclear cataracts; often associated with other features (cardiac defects, deafness)
• Toxoplasmosis, CMV, varicella (less common)

• Down syndrome, Turner syndrome, Patau syndrome (Trisomy 13)
• Nance-Horan syndrome (X-linked)
• Norrie disease

• Autosomal dominant is the most common form of isolated hereditary cataract

Management of Congenital Cataract

• Dense unilateral cataracts require surgery within the first few weeks of life to prevent permanent amblyopia
• Dense bilateral cataracts - surgery within the first 6-10 weeks
• Post-operatively, optical correction (contact lenses or spectacles) and amblyopia treatment (patching the fellow eye) are essential
• Primary posterior capsulotomy and anterior vitrectomy are often performed in young children to prevent posterior capsular opacification

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5. Management of Acquired Cataract

5A. Indications for Surgery

1. Functional - visual acuity reduced to a level that affects the patient's daily activities (most common indication)
2. Medical - lens-induced glaucoma (phacomorphic, phacolytic), lens-induced uveitis, obstruction to view of the posterior segment (e.g., in diabetic retinopathy management)
3. Optical - to correct high refractive error (e.g., unilateral aphakia, refractive lens exchange)

5B. Preoperative Assessment

• Visual acuity - best corrected Snellen or LogMAR chart
• Biometry - measurement of axial length (A-scan ultrasound or optical coherence biometry) and corneal curvature (keratometry) to calculate IOL power
  • Barrett Universal II, Holladay, SRK/T, Haigis formulas commonly used
  • Margin of error: postoperative unaided refraction is within 1.0 D of predicted in ~90% and within 0.5 D in two-thirds of patients
• Corneal assessment - pre-existing endothelial disease warrants caution
• Fundal assessment - particularly if posterior pathology may limit visual recovery
• Pupil dilation - adequacy for surgery
• General health - anticoagulation management, diabetes, fitness for anaesthesia

Refractive Planning

• Emmetropia is typically the desired postoperative refraction
• Many surgeons aim for a small degree of myopia (~-0.25 D) to offset biometry errors
• Monovision - non-dominant eye targeted at ~1-2 D of myopia for near work; dominant eye targeted for emmetropia
• Multifocal IOLs - achieve near, intermediate, and distance vision but can cause glare and loss of contrast sensitivity
• Contralateral eye consideration - target should be within <2.0 D of the fellow eye to avoid anisometropia

5C. Intraocular Lenses (IOLs)

Anatomy of an IOL

• Optic - central refracting element
• Haptics - arms/loops that stabilize the optic by contacting peripheral ocular structures

Positioning

IOL Types

• Monofocal - single focal point; patient needs reading glasses for near
• Toric IOL - corrects pre-existing corneal astigmatism
• Multifocal IOL (diffractive/refractive) - near + distance; risk of glare/haloes
• Extended depth of focus (EDOF) - intermediate and distance; reduced photic phenomena
• Accommodating IOL - attempts to mimic natural accommodation (limited effectiveness)
• Phakic IOL - placed in front of the natural lens (clear lens) for refractive correction

IOL Materials

• Modern IOLs are flexible (foldable) - introduced through a small incision via an injector
• Materials: hydrophobic acrylic (most common), hydrophilic acrylic, silicone, PMMA (rarely used now)
• Hydrophobic acrylic is associated with less posterior capsular opacification (PCO)

5D. Anaesthesia Options

5E. Phacoemulsification - The Gold Standard Procedure

Key Surgical Steps:

1. Corneal incision - usually temporal clear corneal incision; paracentesis for second instrument
2. Viscoelastic injection - maintains anterior chamber depth; protects corneal endothelium
3. Capsulorhexis - circular continuous tear of the anterior capsule (~5.5 mm diameter)
4. Hydrodissection - fluid separates the capsule from the lens cortex
5. Phacoemulsification - nucleus is sculpted and chopped using ultrasonic probe; "divide and conquer" or "stop and chop" technique
6. Irrigation and aspiration (I&A) - removal of residual cortex
7. IOL implantation - folded IOL injected into the capsular bag
8. Viscoelastic removal - prevents post-operative IOP spike

Surgical Parameters

• Ultrasound energy - minimized to reduce corneal endothelial damage; phaco time and cumulative dissipated energy (CDE) are key metrics
• Fluidics - balanced salt solution (BSS); appropriate infusion pressure and aspiration flow rate

5F. Manual (Extracapsular) Cataract Surgery (ECCE / MSICS)

• Used when phacoemulsification is not available or nucleus is too hard for phaco
• ECCE: large limbal incision (~10-12 mm); nucleus expressed manually; IOL implanted; sutured
• Manual Small Incision Cataract Surgery (MSICS): Modified technique; nucleus expressed through a small tunnel incision without sutures; popular in developing world settings for high volume surgery

5G. Femtosecond Laser-Assisted Cataract Surgery (FLACS)

• Laser performs capsulorhexis, corneal incisions, and lens fragmentation
• Benefits: potentially more precise capsulorhexis, reduced phaco energy
• A 2025 meta-analysis (PMID: 40731148) found no clinically significant difference in visual outcomes compared to conventional phacoemulsification in RCTs

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6. Postoperative Complications

Early Complications

Postoperative Endophthalmitis

• Incidence: ~0.1% after cataract surgery
• Most (90%) caused by Gram-positive organisms; Staphylococcus epidermidis most common
• Risk factors: posterior capsule rupture, wound leak, temporal clear corneal incision, adnexal disease, diabetes
• Prophylaxis: intracameral cefuroxime (preferred in Europe) or moxifloxacin at end of surgery; povidone-iodine prep is essential
• Treatment: based on EVSG study results - intravitreal vancomycin + amikacin/ceftazidime; pars plana vitrectomy if light perception only

Posterior Capsule Opacification (PCO)

• Most common long-term complication; occurs in 10-50% within 2-5 years
• Due to proliferation and migration of residual lens epithelial cells (Elschnig pearls)
• Causes visual symptoms similar to the original cataract
• Treatment: Nd:YAG laser posterior capsulotomy - safe, effective outpatient procedure
• Prevention: sharp-edged IOL design (barrier effect), hydrophobic acrylic material, in-the-bag IOL placement

Dysphotopsia

• Positive dysphotopsia - unwanted light perceptions (arcs, streaks, starbursts, haloes) due to internal reflection within the IOL; more common with hydrophobic acrylic
• Negative dysphotopsia - a temporal crescent or shadow; believed to be due to a gap between the IOL and the capsule; resolves spontaneously in most cases
• Management: reassurance; brimonidine for positive; pupil dilation for negative; sulcus IOL repositioning for refractory cases

Other Long-Term Complications

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7. Cataract in Special Situations

High-Risk Eyes

• Pseudoexfoliation syndrome - zonular weakness; risk of zonular dehiscence during surgery; requires iris hooks/Malyugin ring and capsular tension ring (CTR)
• Small pupils - intraoperative floppy iris syndrome (IFIS) associated with tamsulosin; requires iris expansion devices
• High myopia - larger axial length makes biometry less accurate; higher RD risk post-surgery
• Dense mature cataracts - no red reflex; trypan blue used to stain anterior capsule for capsulorhexis visualization
• Corneal pathology - Fuchs endothelial dystrophy; may need combined phaco-DSAEK/DMEK

Paediatric Cataract - Key Points

• Risk of amblyopia is the primary concern
• Dense unilateral cataracts need surgery within 6-8 weeks of birth
• Primary posterior capsulotomy + anterior vitrectomy done at time of surgery
• Contact lens or spectacle correction immediately post-op
• Patching of the fellow eye for amblyopia therapy
• Secondary IOL implantation typically deferred until ~2 years of age

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8. Ectopia Lentis (Lens Dislocation)

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9. Abnormalities of Lens Shape (Associated with Cataract)

• Anterior lenticonus - conical protrusion of anterior lens surface; associated with Alport syndrome (X-linked); progressive - may need surgery
• Posterior lenticonus - more common than anterior; usually unilateral sporadic; progressive opacity often results; "oil droplet" sign on retroillumination
• Lentiglobus - rare unilateral generalized hemispherical deformity
• Microspherophakia - small spherical lens; associated with Marfan, Weill-Marchesani, congenital rubella; complications include lenticular myopia, subluxation
• Lens coloboma - congenital indentation of the peripheral lens from localized zonular deficiency; not a true coloboma

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10. Recent Evidence (PubMed, 2024-2026)

• A 2025 meta-analysis of RCTs (PMID: 40731148, Lee SH et al., Sci Rep) comparing femtosecond laser-assisted cataract surgery (FLACS) to conventional phacoemulsification found no clinically significant difference in visual outcomes, suggesting conventional phaco remains the gold standard.
• Combined microinvasive glaucoma surgery (MIGS) with phacoemulsification in open-angle glaucoma shows modest but significant IOP reduction over phaco alone (PMID: 39089358, Yuan PHS et al., Am J Ophthalmol 2025).

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Summary

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Vernal Keratoconjunctivitis (VKC)

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1. Definition

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2. Epidemiology

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3. Pathogenesis

• IgE pathway: Allergen cross-links IgE on sensitized mast cells in the conjunctiva - degranulation releases histamine, tryptase, prostaglandins, leukotrienes
• Cell-mediated: CD4+ Th2 lymphocytes predominate; they release IL-4, IL-5, IL-13, eotaxin - driving eosinophil recruitment and activation
• Eosinophils: Massively infiltrate the conjunctiva; release major basic protein (MBP) and eosinophil cationic protein (ECP), which cause epithelial toxicity and corneal damage
• Mast cells are increased in the conjunctival epithelium and stroma
• Fibroblast activation leads to collagen deposition forming the fibrovascular core of the giant papillae

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4. Classification

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5. Clinical Features

Symptoms

• Intense itching - the hallmark symptom
• Lacrimation
• Photophobia
• Foreign body sensation / burning
• Thick ropy/mucoid discharge (stringy mucus - pathognomonic)
• Increased blinking

Signs - Palpebral Form

• Conjunctival hyperaemia
• Diffuse velvety papillary hypertrophy on the superior tarsal plate

• Macropapillae (<1 mm) - flat-topped, polygonal appearance; "cobblestone" pattern
• Focal or diffuse whitish inflammatory infiltrates between papillae in intense disease

• Giant papillae (>1 mm) form when adjacent macropapillae amalgamate as dividing septa rupture
• Mucus deposition visible between giant papillae

Signs - Limbal Form

• Gelatinous limbal papillae at the corneoscleral limbus
• Horner-Trantas dots - transient, apically located whitish cellular collections of degenerated eosinophils at the limbal papillae; pathognomonic of limbal VKC

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6. Corneal Complications (Vernal Keratopathy)

Shield ulcer is a sight-threatening emergency - warrants urgent treatment to prevent secondary bacterial infection and permanent scarring.

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7. Diagnosis

• Diagnosis is clinical - investigations are usually not required
• Conjunctival scraping: eosinophils are abundant (eosinophilia on Giemsa stain is supportive)
• Serum total IgE: may be elevated but non-specific
• Skin prick testing / RAST: identifies specific allergens; guides avoidance measures
• Slit-lamp examination is essential for grading severity and detecting corneal complications

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8. Differential Diagnosis

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9. Treatment

Step 1 - Environmental Control / Avoidance

• Avoid identified allergens (dust, pollen, animal dander)
• Cold compresses - reduce histamine release and symptom relief
• Dark glasses / UV protection - reduces photophobia
• Air conditioning in rooms (reduces exposure to hot, dry air and allergens)
• Avoid eye rubbing (triggers mast cell degranulation)

Step 2 - Topical First-Line Therapy (Mild-Moderate Disease)

These should be started 2-3 weeks before allergy season begins for prophylactic effect.

Step 3 - Topical Corticosteroids (Moderate-Severe Disease)

• Prednisolone acetate 1% drops - 4-6 times/day during exacerbations; taper
• Loteprednol etabonate 0.5% - softer steroid; less IOP risk; preferred for maintenance
• Dexamethasone 0.1% ointment - useful for shield ulcers
• Must monitor IOP on any topical steroid

Step 4 - Topical Calcineurin Inhibitors (Steroid-sparing)

• Cyclosporine A 0.05-2% (Restasis, Verkazia 0.1%) - inhibits T-cell activation and cytokine production; excellent for steroid-dependent cases
  • Verkazia (0.1%): approved for severe VKC, 4x/day until resolution
  • Restasis (0.05%): 4x/day
• Tacrolimus 0.03% ointment - also used topically in refractory cases

Step 5 - Systemic Therapy (Severe/Refractory Cases)

• Oral antihistamines - reduce systemic allergic background
• Oral corticosteroids - short courses for very severe acute exacerbations; avoid long-term
• Systemic cyclosporine - for very severe, sight-threatening refractory VKC
• Supratarsal corticosteroid injection (triamcinolone) - directly into the tarsal plate for palpebral giant papillae; effective for refractory cases; reduces papillae size

Step 6 - Management of Shield Ulcer

1. Topical steroid (prednisolone 1% or loteprednol) 4-6x/day
2. Topical antibiotic (trimethoprim/polymyxin B QID, or erythromycin ointment) to prevent secondary infection
3. Cycloplegic (cyclopentolate 1% TID) - reduces ciliary spasm and pain
4. Mechanical debridement of the plaque (superficial keratectomy) if the plaque prevents re-epithelialization
5. Bandage contact lens to protect the epithelium and promote healing
6. Mitomycin C (MMC) - topical 0.02% may be used to prevent recurrence of plaques

Step 7 - Surgical Management

• Surgical debridement / superficial keratectomy of shield ulcer plaques that resist medical treatment
• Papillectomy - rarely required; for very large giant papillae causing mechanical corneal damage
• Cryotherapy to papillae

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10. VKC vs. AKC - Key Comparison

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11. Prognosis

• 95% undergo spontaneous remission in the late teens
• The remaining 5% may develop atopic keratoconjunctivitis (AKC), which is a more severe, potentially blinding condition
• With corneal complications (especially shield ulcers), permanent subepithelial scarring and reduced vision are possible if treatment is delayed
• Regular follow-up is essential during active disease; steroid monitoring (IOP checks) is mandatory

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Summary Table

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