Senile (Age-Related) Cataract

Anatomy of the Lens (Relevant Background)

• Capsule - outer elastic basement membrane
• Epithelial cells - single anterior layer (the germinative zone produces new lens fibres throughout life)
• Cortex - superficial newer fibres
• Nucleus - central older, compacted fibres

Pathogenesis

• Oxidative damage - ROS attack lens crystallins, leading to protein aggregation and high-molecular-weight complexes that scatter light
• Glycation - non-enzymatic glycosylation of lens proteins (relevant in diabetes, where glucose is converted to sorbitol by aldose reductase, creating osmotic stress)
• Dehydration and ionic imbalance - breakdown of Na+/K+-ATPase pump leads to water influx and cortical hydration
• Urochrome pigment deposition - yellowing/browning of the nucleus with aging

Types / Morphological Classification

1. Posterior Subcapsular Cataract (PSC)

• Lies just in front of the posterior capsule
• Granular or plaque-like on oblique slit lamp; black and vacuolated on retroillumination (vacuoles = swollen Wedl/bladder cells - migratory lens epithelial cells)
• Located at the nodal point of the eye - disproportionately affects vision even at early stages
• Key symptom: glare (from oncoming headlights), worse with miosis (near work, bright sunlight)
• Also caused by: steroids, diabetes, radiation, retinitis pigmentosa

2. Nuclear Sclerotic Cataract

• Exaggeration of normal aging - compaction and hardening of the nucleus
• Yellowish hue due to urochrome pigment deposition (best seen on oblique slit beam)
• Advanced cases turn brown (brunescent) or rarely black (nigra)
• Classic feature: myopic shift ("second sight of the aged") - patient can suddenly read without spectacles because increased refractive index of nucleus causes index myopia
• Retroillumination shows preserved red reflex but subtle nucleus-cortex demarcation

3. Cortical Cataract

• Involves anterior, posterior or equatorial cortex
• Starts as clefts and vacuoles due to cortical hydration
• Progresses to cuneiform (wedge-shaped) or spoke-like radial opacities, typically beginning in the inferonasal quadrant
• Seen on slit lamp as spokes radiating from the lens equator
• Glare is common, similar to PSC

4. Christmas Tree Cataract

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

Stages of Senile Cataract (Classical)

Slit Lamp Appearances

• The slit beam passes through: anterior capsule → anterior cortex → nucleus → posterior cortex → posterior capsule
• Cortical cataracts: spoke-like opacities from lens equator
• Nuclear cataracts: yellow/amber central hue
• PSC: clustered punctate vacuoles, best seen on retroillumination

Symptoms

• Gradual, painless decrease in vision
• Glare (especially PSC and cortical types)
• Monocular diplopia or polyopia
• Altered colour perception (yellowing in nuclear cataracts)
• "Second sight" - temporary improvement in near vision (nuclear myopia)
• Difficulty with night driving

Systemic/Risk Factor Associations

Investigations / Workup

1. Visual acuity - Snellen chart
2. Slit lamp biomicroscopy - type and density of opacity
3. Retroillumination - best for PSC
4. Glare testing - functional impact assessment
5. Dilated fundus examination - to rule out co-existing retinal pathology that would limit visual recovery post-surgery
6. Biometry (pre-operatively):
   • Keratometry - corneal curvature in dioptres
   • A-scan ultrasonography or optical coherence biometry (partial coherence interferometry) - axial length measurement
   • IOL power calculated using formulae (SRK/T, Holladay, Barrett Universal II, etc.)

Management

Conservative

• Updated spectacle correction for early cataracts (myopic shift in nuclear cataract)
• Anti-glare glasses
• No proven medical therapy to halt progression

Surgical Indications

• Visual: opacity sufficient to impair daily activities (primary indication)
• Medical: phacolytic glaucoma, phacomorphic glaucoma, cataract preventing fundus monitoring/treatment
• Clear lens exchange for refractive error management

Surgical Techniques

Phacoemulsification (Gold Standard)

• Ultrasonic fragmentation and aspiration of the lens nucleus through a small (~2.4-2.8 mm) self-sealing corneal incision
• Followed by foldable IOL implantation into the capsular bag
• No sutures required; rapid recovery
• Risk of intraoperative floppy iris syndrome with systemic alpha-blockers (e.g. tamsulosin)

Manual Small Incision Cataract Surgery (MSICS)

• Variant of extracapsular extraction (ECCE) used in resource-limited settings
• Nucleus expressed intact through a larger but self-sealing scleral tunnel incision
• No phaco machine needed; good visual outcomes; widely used in India

Extracapsular Cataract Extraction (ECCE)

• Larger limbal incision; requires sutures; more astigmatism
• Less common now; still used for very dense (brunescent) nuclei

Intracapsular Cataract Extraction (ICCE)

• Entire lens including capsule removed; largely obsolete
• No capsular support for posterior chamber IOL

Intraocular Lens (IOL) Types

• Monofocal IOL - standard; corrects for one distance (usually distance)
• Toric IOL - corrects pre-existing corneal astigmatism
• Multifocal/bifocal IOL - provides range of focal distances; higher dysphotopsia rate
• Accommodative IOL - attempts to mimic accommodation (limited clinical effect)
• Light-adjustable IOL - refractive power adjusted post-implantation using UV light

Complications of Cataract Surgery

Epidemiology / Public Health

• Senile cataract is the most common cause of blindness in India and worldwide
• In India, cataract occurs ~10 years earlier than in Europe/America - Park's Textbook of Preventive & Social Medicine
• The "National Programme for Control of Blindness" targets cataract surgical rate (CSR) as a key metric
• Cataract surgical coverage remains suboptimal in Indigenous populations and resource-poor settings (BMJ Open Ophthalmol, 2025)

Senile Cataract

Definition

Etiology / Risk Factors

• Old age (most common)
• UV light exposure
• Diabetes mellitus
• Malnutrition
• Smoking, dehydration

Types (Morphological)

Stages

Iris shadow test: In immature cataract - iris casts a shadow on the lens (oblique illumination). In mature cataract - no shadow (lens fully opaque).

Symptoms

• Gradual, painless diminution of vision
• Glare / photophobia
• Monocular diplopia
• "Second sight" (nuclear type - myopic shift)
• Altered colour perception

Diagnosis

• Slit lamp biomicroscopy
• Retroillumination (best for PSC)
• Fundus examination (dilated)
• Biometry (pre-op: keratometry + axial length for IOL power)

Treatment

Surgical (only definitive treatment)

Methods:

1. Phacoemulsification - Gold standard
   • Ultrasound breaks up nucleus; aspirated through 2.4-3 mm incision
   • Foldable IOL implanted in capsular bag
   • No sutures; rapid recovery
2. MSICS (Manual Small Incision Cataract Surgery)
   • Popular in India; no phaco machine needed
   • Good outcomes; cost-effective
3. ECCE (Extracapsular Cataract Extraction)
   • Larger incision; sutures needed
   • Used for very hard (brunescent) nuclei
4. ICCE (Intracapsular) - Obsolete

Complications of Surgery

• PCO (Posterior Capsular Opacification / "after-cataract") - treated by Nd:YAG laser
• Endophthalmitis (rare, serious)
• Cystoid macular oedema
• Posterior capsule rupture
• Retinal detachment

Important Exam Points

• Mature cataract = no iris shadow, no red reflex, white pupil (leukocoria)
• Hypermature = risk of phacolytic glaucoma (lens proteins leak out → macrophage blockage of trabecular meshwork)
• "Second sight" = nuclear myopia (patient reads without glasses temporarily)
• PSC = worst glare; worst in bright light / near work
• Morgagnian cataract = liquefied cortex with sunken brown nucleus