Senile (Age-Related) Cataract

Anatomy of the Lens

• Lens capsule — outermost, elastic basement membrane
• Lens epithelium — single layer of cells beneath the anterior capsule; the only mitotically active layer
• Lens cortex — newer, peripheral lens fibres (soft)
• Lens nucleus — older, central compacted lens fibres (harder with age)

Pathogenesis

• Adams and Victor's Principles of Neurology, 12th Ed.: "lens proteins denature and degrade over time" as the fundamental mechanism.
• Robbins, Cotran & Kumar Pathologic Basis of Disease: accumulation of urochrome pigment renders the nucleus brown, distorting colour perception — the yellowish hues of Rembrandt's later paintings may reflect his nuclear sclerotic cataracts.

Risk Factors

• Advancing age (most important)
• Female sex
• Genetic predisposition

• Ultraviolet-B radiation exposure
• Smoking
• Alcohol
• Dehydration and diarrhoeal episodes
• Poor nutrition (low antioxidant intake)

• Diabetes mellitus (accelerates all types)
• Myotonic dystrophy
• Atopic dermatitis
• Neurofibromatosis type 2
• Wilson disease, galactosaemia

• Corticosteroids (systemic or topical) → posterior subcapsular cataract
• Phenothiazines
• Amiodarone
• Radiation (ionising and UV)
• Trauma

Classification by Morphology (Types of Senile Cataract)

1. Posterior Subcapsular (PSC) Cataract

• Located just anterior to the posterior capsule
• Slit lamp: granular or plaque-like on oblique beam; black with vacuoles on retroillumination (Wedl/bladder cells = swollen migratory epithelial cells)
• Sits at the nodal point → disproportionate visual impact even when small
• Symptoms: glare (from oncoming headlights), worse with miosis (near vision, bright sunlight)
• Common with corticosteroids, diabetes, radiation, NF2

2. Nuclear Sclerotic Cataract

• Exaggeration of the normal ageing process — most common senile type
• Gradual yellowing (urochrome) → amber → brown (brunescent) → rarely black
• Best assessed with an oblique slit-lamp beam
• Retroillumination shows good red reflex with subtle nucleus–cortex distinction
• Associated with myopic shift ("second sight of the aged"): increased refractive index of the nucleus allows previously presbyopic patients to read again without spectacles
• Nuclear grading scale (SPONCS): Grade 1–5

3. Cortical Cataract

• Involves anterior, posterior, or equatorial cortex
• Begins as clefts and vacuoles due to cortical hydration → typical cuneiform (wedge-shaped) or radial spoke-like opacities, often starting infranasally
• Glare is prominent
• On slit-lamp: spoke-like opacities radiating from periphery toward centre

4. Anterior Subcapsular Cataract

• Lies directly under the anterior capsule
• Associated with fibrous metaplasia of the lens epithelium
• Seen with chronic anterior uveitis (posterior synechiae deprive epithelium of aqueous contact), atopic dermatitis (shield-like plaque)

5. Christmas Tree Cataract

• Uncommon; polychromatic needle-like formations in deep cortex and nucleus
• Associated with myotonic dystrophy

Stages of Maturity

Clinical Features

• Gradual, painless, progressive visual blur
• Glare and halos (especially PSC and cortical)
• Monocular diplopia or polyopia (irregular refractive indices)
• Colour desaturation (nuclear cataract — blue-end of spectrum filtered)
• "Second sight" (myopic shift with nuclear cataract — temporary improvement in near vision)
• Difficulty with night driving

• Reduced visual acuity (Snellen chart)
• No afferent pupillary defect — its presence implies posterior pole pathology, not cataract alone
• Absent or diminished red reflex on direct ophthalmoscopy (mature/dense cataract)
• Slit-lamp biomicroscopy: definitive characterisation of type, density, location

Complications of Untreated Cataract

1. Phacolytic glaucoma — mature/hypermature cataract leaks lens proteins through intact capsule → macrophages engulf them → block trabecular meshwork → open-angle glaucoma
2. Phacomorphic glaucoma — intumescent (swollen) lens pushes iris forward → acute angle closure
3. Phacoanaphylactic uveitis — lens protein leakage → autoimmune granulomatous uveitis
4. Amblyopia — in unilateral dense cataract, especially in children

Management

Indications for Surgery

1. Visual: Opacity sufficient to interfere with daily activities (most common)
2. Medical: Phacolytic/phacomorphic glaucoma, media opacity preventing fundus monitoring/treatment
3. Elective refractive: Clear lens exchange for refractive error correction

Preoperative Assessment

• Biometry (keratometry + axial length) → IOL power calculation
  • Optical coherence biometry (partial coherence interferometry) is the preferred method
  • A-scan ultrasonography as alternative
  • Multiple formulae used (SRK-T, Hoffer Q, Haigis, Barrett Universal II)
• Check for alpha-blocker use (tamsulosin) → risk of intraoperative floppy iris syndrome (IFIS)
• Pupillary dilation adequacy; corneal endothelial cell count; macular OCT if suspect macular disease
• Manage anticoagulants per local protocol

Surgical Technique

Phacoemulsification (Standard)

1. Small self-sealing corneal incision (~2.4–2.8 mm)
2. Viscoelastic injection into anterior chamber
3. Continuous curvilinear capsulorhexis (CCC) — circular tear of anterior capsule
4. Hydrodissection — fluid wave separates nucleus from cortex
5. Phacoemulsification — ultrasonic probe emulsifies and aspirates the nucleus
6. Irrigation/aspiration of residual cortex
7. Intraocular lens (IOL) insertion into the capsular bag
8. Wound closure (usually self-sealing, no sutures)

Extracapsular Cataract Extraction (ECCE)

• Larger incision; nucleus expressed intact; less used now
• Still preferred in very hard (brunescent) nuclei or when phaco is unavailable

Intracapsular Cataract Extraction (ICCE)

• Entire lens including capsule removed; rarely performed today

Intraocular Lenses (IOL)

• Monofocal (most common) — corrects for one distance; glasses needed for others
• Multifocal — corrects near and distance; risk of glare/halos
• Extended depth of focus (EDOF) — intermediate and distance
• Toric — corrects pre-existing astigmatism
• Target refraction: usually emmetropia or slight myopia

Complications of Cataract Surgery

Posterior Capsular Opacification (PCO)

• Most common late complication — occurs in up to 20–40% within 5 years
• Residual lens epithelial cells migrate onto the posterior capsule → "Elschnig pearls" or fibrous opacity
• Treatment: Nd:YAG laser posterior capsulotomy (outpatient, definitive)

Special Situations

Cataract in Diabetes

• Glucose → sorbitol (aldose reductase) → osmotic hydration → cortical vacuoles → opacities
• Classic diabetic (snowflake) cataract: white cortical flakes in young patients; may resolve with glucose control
• Age-related cataract occurs sooner in diabetics; nuclear sclerosis progresses rapidly
• Pre-existing diabetic macular oedema worsens post-surgery — monitor carefully

Morgagnian Cataract

Differential Diagnosis of Lens Opacity

Prognosis