Cataract

Anatomy & Pathophysiology

Classification

1. Age-Related (Most Common)

Posterior Subcapsular Cataract (PSC)

• Located just in front of the posterior capsule
• Granular or plaque-like on slit lamp; black and vacuolated on retroillumination
• Vacuoles are swollen "bladder" (Wedl) cells - migratory lens epithelial cells
• Because it sits at the nodal point of the eye, it has a disproportionately severe effect on vision
• Characteristic symptom: glare from car headlights; worsens with miosis (near tasks, bright light)

Anterior Subcapsular Cataract

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

Nuclear Sclerotic Cataract

• Exaggeration of normal aging
• Yellowish hue due to deposition of urochrome pigment
• Associated with myopia (index myopia) - "second sight"
• Advanced cases: brown nucleus (brunescent); rarely black (cataracta nigra)
• Best assessed with oblique slit-lamp beam

Cortical Cataract

• Involves anterior, posterior, or equatorial cortex
• Starts as clefts and vacuoles between lens fibers due to cortical hydration
• Typical cuneiform (wedge-shaped) or radial spoke-like opacities
• Often begins in the inferonasal quadrant
• Glare is a common symptom

2. Cataract Maturity

3. Congenital Cataract

• Present at birth or developing in early childhood
• Can be isolated or associated with systemic conditions (Down syndrome, galactosemia, rubella, TORCH infections)
• Must be treated promptly to prevent amblyopia

4. Secondary (Complicated) Cataract

• Chronic anterior uveitis - most common cause; posterior and anterior opacities; steroids also contribute
• Acute angle-closure glaucoma - glaukomflecken (small grey-white subcapsular opacities, focal lens epithelial infarcts); pathognomonic of previous acute attack
• High myopia - posterior subcapsular opacity and early nuclear sclerosis

5. Cataract in Systemic Disease

6. Drug-Induced

• Steroids (systemic or topical): posterior subcapsular cataract
• Phenothiazines, amiodarone, miotics (long-term)

7. Traumatic

• Blunt trauma: rosette-shaped PSC
• Penetrating injury: direct cortical opacification
• Electric shock, radiation, infrared (glassblower's cataract)

Symptoms

• Reduced visual acuity (initially correctable with spectacles)
• Loss of contrast sensitivity
• Altered colour perception - particularly impaired blue perception
• Glare and haloes (especially at night - headlight glare)
• Monocular diplopia (especially with point light sources)
• Difficulty in low-light conditions
• Nuclear cataract: myopic shift ("second sight")

Diagnosis

• Slit-lamp examination: gold standard - type, location, density
• Retroillumination: best for PSC and cortical opacities
• Visual acuity testing: Snellen chart
• Contrast sensitivity testing
• Potential acuity meter (PAM): estimates post-op visual potential
• B-scan ultrasound: when fundus view is obscured

Treatment

Conservative

• Spectacle correction for mild cases
• Increased illumination for reading

Surgical (Definitive)

• Small incision (2-3 mm)
• Ultrasonic fragmentation and aspiration of lens nucleus
• Foldable intraocular lens (IOL) implanted into the capsular bag
• Outpatient procedure
• Results equivalent to femtosecond laser-assisted cataract surgery (FLACS) for standard cases

• Laser performs capsulorrhexis, lens fragmentation, and corneal incisions
• No clear superiority over phacoemulsification in standard cases

Intraocular Lens (IOL) Options

• Monofocal IOL: single focus point (usually distance)
• Multifocal/trifocal IOL: near and distance vision
• Toric IOL: corrects pre-existing astigmatism
• Extended depth of focus (EDOF) IOL

Surgical Timing

• In general, the worse eye is operated on first
• The second eye is operated on as its cataract worsens and monocularity becomes a functional issue
• In children with congenital cataract: surgery within weeks of birth to prevent amblyopia, followed by aggressive amblyopia treatment

Complications of Surgery

• Posterior capsule opacification (PCO) - "after-cataract": most common late complication; lens epithelial cells migrate onto the posterior capsule; treated with Nd:YAG laser posterior capsulotomy
• Endophthalmitis: rare but serious infection
• Cystoid macular edema (CME)
• Retinal detachment: increased risk in high myopes
• Corneal decompensation (bullous keratopathy)
• Dry eye post-surgery (recent systematic review 2025, PMID 39806338 confirms this as a significant complication)
• Dropped nucleus (posterior dislocation of lens fragments)
• Posterior capsule rupture

Prognosis