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CATARACT

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DEFINITION

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ANATOMY OF THE LENS (Relevant to Cataract)

• Zonules suspend the lens in position.
• Capsule: an acellular membrane enclosing the entire lens.
• Epithelium: cuboid cells beneath the anterior capsule, extending to the equator. Cells in the germinative zone divide continuously and differentiate into lens fibres.
• Lens substance: central nucleus surrounded by cortex.
• The lens has no blood supply - it depends entirely on the aqueous humour for nutrition.

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CLASSIFICATION OF CATARACT

A. Based on Aetiology

1. Age-related (senile)
2. Congenital
3. Traumatic
4. Secondary (complicated)
5. Cataract in systemic disease
6. Drug-induced (e.g., steroids, chlorpromazine)
7. Radiation-induced

B. Based on Morphology

1. Subcapsular (anterior / posterior)
2. Nuclear
3. Cortical
4. Christmas tree

C. Based on Maturity (Senile Cataract)

1. Immature
2. Mature
3. Hypermature
4. Morgagnian

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SYMPTOMS OF CATARACT

• Reduced visual acuity (initially correctable with glasses)
• Loss of contrast sensitivity
• Change in colour perception - particularly impaired perception of blue colours
• Glare - due to light scattering; worsened at night (headlight glare during driving)
• Monocular diplopia - especially on looking at point sources of light
• Difficulty in dim light / poor night vision
• Myopic shift (in nuclear cataract) - patient may be able to read without glasses again ("second sight of the aged")

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AGE-RELATED (SENILE) CATARACT

1. Posterior Subcapsular Cataract (PSC)

• Located just anterior to the posterior capsule
• Granular or plaque-like appearance on oblique slit-lamp biomicroscopy
• Appears black and vacuolated on retroillumination; vacuoles = swollen Wedl cells (bladder cells = migratory lens epithelial cells)
• Due to its position at the nodal point of the eye, PSC causes profound visual impairment disproportionate to its size
• Symptoms: glare (worsened by miosis - e.g., in bright sunlight or near vision)

2. Anterior Subcapsular Cataract

• Lies directly under the lens capsule
• Associated with fibrous metaplasia of the lens epithelium

3. Nuclear Sclerotic Cataract

• An exaggeration of normal ageing
• Myopic shift due to increased refractive index of nucleus → "second sight of the aged"
• Yellowish hue due to deposition of urochrome pigment → may turn brown (brunescent), rarely black
• Best assessed with oblique slit-lamp beam
• On retroillumination: good red reflex but subtle nucleus-cortex demarcation

4. Cortical Cataract

• Involves anterior, posterior, or equatorial cortex
• Opacities start as clefts and vacuoles due to cortical hydration
• Results in typical cuneiform (wedge-shaped) or spoke-like radial opacities
• Often starts in the inferonasal quadrant
• Glare is a common symptom

5. Christmas Tree Cataract

• Polychromatic (multicoloured) needle-like deposits in the deep cortex/nucleus
• Associated with myotonic dystrophy (though can occur in others)
• Characteristic sparkling, multicoloured sheen on slit-lamp examination

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STAGES OF SENILE CATARACT (Maturity)

Exam note: Hypermature cataracts can leak lens proteins causing phacolytic glaucoma (macrophages clog trabecular meshwork). Morgagnian cataracts can cause phacomorphic glaucoma by pupillary block.

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SLIT-LAMP APPEARANCE

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CATARACT IN SYSTEMIC DISEASE

1. Diabetes Mellitus

• Hyperglycaemia → high aqueous glucose → glucose diffuses into lens → metabolized to sorbitol → osmotic overhydration of lens
• Early: refractive fluctuation (hyperglycaemia → myopia; hypoglycaemia → hypermetropia)
• Classic diabetic cataract (rare, in young): snowflake cortical opacities - may mature within days or resolve spontaneously
• Age-related cataract occurs earlier in diabetics
• Nuclear sclerosis is common and progresses rapidly
• ~1 in 5 cataract surgery patients has diabetes

2. Myotonic Dystrophy

• ~90% develop fine iridescent cortical opacities in the 3rd decade (sometimes like Christmas tree cataract)
• Progress to visually disabling star-shaped wedge-shaped cortical + subcapsular opacities by the 5th decade

3. Atopic Dermatitis

• ~10% of severe cases develop cataracts in the 2nd-4th decades
• Characteristic: shield-like dense anterior subcapsular plaque wrinkling the anterior capsule
• Posterior subcapsular opacities may also occur

4. Neurofibromatosis Type 2

• Early cataract in >60% of patients
• Opacities: posterior subcapsular, capsular, cortical, or mixed
• Tend to develop in early adulthood

5. Steroid-induced

• Prolonged topical/systemic/inhaled corticosteroids → posterior subcapsular cataract

6. Wilson's Disease

• Sunflower cataract - greenish-brown pigment deposits in anterior lens capsule (due to copper deposition)

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SECONDARY (COMPLICATED) CATARACT

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TRAUMATIC CATARACT

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CONGENITAL CATARACT

Epidemiology

• Occurs in ~3 in 10,000 live births
• 2/3 are bilateral; 1/3 are unilateral (usually sporadic)
• Aetiology: 1/3 systemic disease; 1/3 inherited; 1/3 unknown cause
• Autosomal dominant (AD) is the most common inheritance pattern

Associated Metabolic Disorders

Associated Intrauterine Infections (TORCH)

Morphological Types of Congenital Cataract

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MANAGEMENT OF CATARACT

Indications for Surgery

1. Visual: when cataract causes sufficient visual disability (functional indications)
2. Medical: phacolytic glaucoma, phacomorphic glaucoma, subluxated lens causing uveitis
3. Social: to allow fundus examination (e.g., diabetic retinopathy monitoring)
4. Congenital: dense unilateral/bilateral cataract - surgery urgently needed to prevent amblyopia

Preoperative Assessment

• Diabetes - optimize glycaemic control
• Hypertension - defer if systolic >170 mmHg / diastolic >100 mmHg
• Anticoagulants (e.g., warfarin, aspirin) - consider stopping based on risk
• Alpha-blockers (e.g., tamsulosin) - major cause of Intraoperative Floppy Iris Syndrome (IFIS)

• Visual acuity (Snellen chart)
• Cover test (rule out amblyopia/squint)
• Pupillary responses (cataract never causes RAPD - its presence implies posterior segment pathology)
• Slit-lamp examination (cornea, AC depth, pupil dilation, lens type)
• Fundal examination (macular pathology, retinal detachment)
• Biometry - IOL power calculation (using A-scan ultrasound or optical biometry)

Anaesthesia Options

1. Topical (most common for routine phacoemulsification)
2. Sub-Tenon's/peribulbar/retrobulbar (regional)
3. General anaesthesia (in children, uncooperative patients)

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SURGICAL TECHNIQUES

1. Intracapsular Cataract Extraction (ICCE) - Historical

• Entire lens including capsule removed through a large incision
• Now largely abandoned
• Complications: vitreous loss, aphakia, bullous keratopathy

2. Extracapsular Cataract Extraction (ECCE)

• Nucleus expressed through a large (~10-12 mm) limbal incision; posterior capsule left intact
• IOL implanted in the capsular bag
• Still used for very hard (brunescent/black) nuclei

3. Manual Small-Incision Cataract Surgery (MSICS)

• Scleral tunnel incision (~6-7 mm) - self-sealing
• Nucleus expressed through the tunnel without phacoemulsification
• Widely used in developing countries (cost-effective)
• Technique: scleral tunnel → anterior capsulotomy (can-opener or manual CCC) → nucleus expression → cortical aspiration (Simcoe cannula) → IOL implantation

4. Phacoemulsification (Gold Standard)

1. Corneal/scleral incision (main port + side port)
2. Injection of OVD (ophthalmic viscosurgical device/viscoelastic) to maintain AC
3. Continuous Curvilinear Capsulorhexis (CCC) - circular tear of anterior capsule using bent needle/capsulorrhexis forceps
4. Hydrodissection - BSS injected under capsule to free cortical-capsular adhesions
5. Hydrodelineation - separates nucleus from epinucleus
6. Phacoemulsification of nucleus (various techniques: divide-and-conquer, stop-and-chop, phaco-chop)
7. Irrigation and aspiration (I&A) of cortical remnants
8. IOL implantation into the capsular bag
9. OVD removal and wound hydration/closure

• Peristaltic pump: flow-controlled; vacuum builds only on occlusion; independent adjustment of flow rate (AFR)
• Venturi pump: vacuum-controlled; synchronized vacuum and AFR; no independent AFR adjustment
• Phaco handpiece with titanium needle + fluid-cooling sleeve

5. Femtosecond Laser-Assisted Cataract Surgery (FLACS)

• Laser performs: capsulotomy, nuclear fragmentation, and corneal incisions with high precision
• Advantages: reproducible capsulotomy, reduced phaco energy, astigmatism correction
• Limitations: cost, risk of incomplete capsulotomy

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INTRAOCULAR LENSES (IOL)

Types

IOL Power Calculation

• Optical biometry (IOLMaster) - preferred, non-contact
• A-scan ultrasound - contact/immersion
• Formulae: SRK/T (most widely used), Holladay, Hoffer Q, Barrett Universal II

IOL Placement

• In-the-bag (capsular bag): ideal position
• Ciliary sulcus: used if posterior capsule torn; requires 3-piece IOL (not 1-piece)
• Optic capture through capsulorhexis can be done for stabilization

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COMPLICATIONS OF CATARACT SURGERY

Intraoperative

Early Postoperative

Late Postoperative

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POSTERIOR CAPSULAR OPACIFICATION (PCO) - AFTER-CATARACT

• Most common late complication of cataract surgery
• Occurs due to proliferation of residual lens epithelial cells (particularly Elschnig pearls = Wedl cells)
• Patient presents with gradual painless decrease in vision weeks to months after surgery
• Slit-lamp: pearl-like opacities on posterior capsule
• Treatment: Nd:YAG laser posterior capsulotomy
  • Power: start at 1 mJ/pulse
  • Pattern: cruciate or circumferential
  • Opening size: ~4-5 mm (= dilated pupil size)
  • Complications of YAG: IOP spike, IOL pitting, retinal detachment, CMO

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CONGENITAL CATARACT - MANAGEMENT

Urgency

• Dense bilateral cataract: surgery within first 6-8 weeks of life to prevent deprivation amblyopia
• Dense unilateral cataract: surgery as soon as possible (ideally within first 6 weeks); more aggressive amblyopia treatment needed post-surgery

Surgical Technique in Children

• Posterior capsulectomy + anterior vitrectomy performed at time of primary surgery (posterior capsule opacifies rapidly in children)
• Primary IOL implantation controversial in children <2 years; contact lenses/aphakic glasses used instead

Post-surgical Management

• Optical rehabilitation: aphakic glasses / contact lenses / IOL
• Amblyopia treatment (patching of fellow eye) - critical for unilateral cataract

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DRUGS CAUSING CATARACT (Drug-induced)

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KEY EXAM POINTS TO REMEMBER

1. Cataract = commonest cause of reversible blindness worldwide
2. PSC is most visually disabling relative to size (nodal point location)
3. "Second sight of the aged" = nuclear cataract → myopic shift
4. Morgagnian cataract = liquefied cortex + sunken nucleus (hypermature)
5. Glaukomflecken = pathognomonic of previous acute ACG
6. Oil droplet cataract = galactosaemia (treatable by diet!)
7. Congenital rubella = pearly nuclear cataract; live virus in lens years after birth (beware during surgery)
8. IFIS = caused by alpha-1 blockers (tamsulosin) - always take drug history
9. After-cataract (PCO) = treated by Nd:YAG capsulotomy
10. Endophthalmitis = most feared early post-op complication; intravitreal vancomycin + ceftazidime
11. Phaco = phacoemulsification via ultrasonic vibration; self-sealing small incision; gold standard
12. IOL power = calculated by optical biometry (IOLMaster); SRK/T formula most used
13. Cataract NEVER causes RAPD - its presence implies significant posterior segment disease

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