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Cataract - Complete MBBS Ophthalmology Notes

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1. DEFINITION & IMPORTANCE

There is NO medical treatment to prevent or reverse cataract - surgery is the only cure.

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2. ANATOMY OF THE LENS (Quick Recap)

LENS STRUCTURE - Mnemonic: "CZEG"
C - Capsule (acellular, outermost)
Z - Zonules (hold lens in position)
E - Epithelium (cuboid cells under anterior capsule)
G - Germinative zone (cells divide → lens fibers)

• Lens substance = Central nucleus + surrounding cortex
• Anterior capsule is thicker than posterior capsule
• The lens is avascular - nutrition comes from aqueous humor

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3. SYMPTOMS OF CATARACT

• Symptoms worsen with miosis (bright light, near work) - especially PSC
• Symptoms develop slowly and insidiously

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4. TYPES OF AGE-RELATED (SENILE) CATARACT

A. Subcapsular Cataract (Posterior > Anterior)

• Posterior subcapsular (PSC): Granular/plaque-like opacity just in front of posterior capsule
  • Appears black and vacuolated on retroillumination
  • Vacuoles = Bladder (Wedl) cells - swollen migratory epithelial cells
  • Worst visual impact - located at nodal point of eye
  • Causes profound glare; worsened by miosis and near vision
  • Classic causes: Steroids, radiation, diabetes
• Anterior subcapsular: Fibrous metaplasia of lens epithelium

B. Nuclear Sclerotic Cataract

• Exaggeration of normal aging
• Yellowish hue due to urochrome pigment deposition
• Causes myopic shift → "Second sight of the aged" (elderly patients can read without glasses again!)
• Best assessed with oblique slit lamp beam
• Advanced: nucleus turns brown (brunescent), rarely black (black cataract)
• Red reflex preserved on retroillumination

C. Cortical Cataract

• Clefts and vacuoles between lens fibers due to cortical hydration
• Typical cuneiform (wedge-shaped) or spoke-like opacities
• Often start in inferonasal quadrant first
• Glare is a common symptom

D. Christmas Tree Cataract (uncommon)

• Polychromatic needle-like formations in deep cortex and nucleus
• Associated with myotonic dystrophy

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5. MATURITY STAGES OF CATARACT

Phacolytic glaucoma = leaking lens proteins clog trabecular meshwork in hypermature cataract Phacomorphic glaucoma = swollen immature/intumescent cataract causes pupil block → angle closure

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6. CATARACT IN SYSTEMIC DISEASES

Steroid cataract = PSC - easy to remember: Steroids → PSC (same initials, reversed)

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7. TRAUMATIC CATARACT

Remember: Vossius ring = iron ring on anterior lens after blunt trauma (from iris pigment impact)

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8. CONGENITAL CATARACT

Rule of Thirds:

1/3 - Systemic disease
1/3 - Inherited (AD most common)
1/3 - Unknown cause

• 2/3 are bilateral
• Unilateral = usually sporadic, otherwise healthy infant

Metabolic Causes - Mnemonic: "GLM"

Intrauterine Infections - Mnemonic: "TORCH"

Rubella triad: "3 C's" - Cataract, Cardiac defects (PDA), Cochlear deafness

Other Systemic Associations for Congenital Cataract:

• Down syndrome (Trisomy 21) - Brushfield spots + cataract
• Turner syndrome - cataract
• Nance-Horan syndrome - X-linked, dense cataract + dental abnormalities
• Marfan syndrome - ectopia lentis (subluxed lens, NOT cataract per se)

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9. SECONDARY (COMPLICATED) CATARACT

• Uveitis (chronic) - PSC most common
• Retinitis pigmentosa - PSC
• Acute angle-closure glaucoma - glaukomflecken (white anterior subcapsular deposits)
• High myopia - nuclear cataract
• Intraocular tumors

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10. INVESTIGATIONS BEFORE CATARACT SURGERY

1. Visual acuity - Snellen chart
2. IOL power calculation - A-scan biometry + keratometry (SRK/T, Holladay, Haigis formulas)
3. Slit lamp examination - assess type, density, corneal endothelium
4. B-scan ultrasound - if posterior pole not visible
5. Specular microscopy - endothelial cell count (important if Fuchs' dystrophy suspected)
6. Blood glucose - especially if diabetic
7. No routine blood tests or ECG needed for local anaesthesia

Important clinical point: Cataract NEVER causes afferent pupillary defect (APD). If APD is present, there is significant posterior pole pathology (retinal/optic nerve disease).

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11. SURGICAL OPTIONS

A. Phacoemulsification ("Phaco") - GOLD STANDARD

• High-frequency ultrasound probe emulsifies the lens nucleus
• Small incision (~2.2-2.8 mm), self-sealing
• IOL inserted through the same incision
• Advantages: Fast recovery, minimal astigmatism, day-case procedure

B. Small Incision Cataract Surgery (SICS)

• Manual technique; slightly larger incision (~5-7 mm)
• No ultrasound needed - used in dense/hard cataracts
• More suitable for developing world settings

C. ECCE (Extracapsular Cataract Extraction)

• Larger incision (~10-12 mm), requires sutures
• Used when nucleus is too hard for phaco
• Higher astigmatism, longer recovery

D. ICCE (Intracapsular Cataract Extraction) - HISTORICAL

• Entire lens + capsule removed
• No longer routinely performed
• Risk of vitreous prolapse; aphakia requires thick "pebble" glasses

Preferred order for MBBS: Phaco > SICS > ECCE > ICCE

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12. INTRAOCULAR LENSES (IOL)

• Standard IOL material: Hydrophobic/hydrophilic acrylic
• Power calculated using: A-scan + keratometry

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13. COMPLICATIONS

Intraoperative:

• Posterior capsule rupture (PCR) - most common serious complication
• Vitreous loss
• Zonular dialysis
• Suprachoroidal hemorrhage (expulsive hemorrhage - rare, catastrophic)
• IFIS (Intraoperative Floppy Iris Syndrome) - due to tamsulosin (alpha-blocker)

Postoperative - Early:

• Endophthalmitis (most feared) - causative organism: Staphylococcus epidermidis (commonest)
• Corneal edema
• Raised IOP (steroid response or retained viscoelastic)
• Uveitis
• Wound leak

Postoperative - Late:

• Posterior Capsule Opacification (PCO) - COMMONEST late complication
  • "After-cataract" or secondary cataract
  • Caused by residual lens epithelial cells (Elschnig's pearls)
  • Treatment: Nd:YAG laser capsulotomy
• Cystoid Macular Edema (CME) - Irvine-Gass syndrome
• Retinal detachment (especially in myopes)
• Glaucoma
• IOL dislocation

Mnemonic for late complications: "PCO GRIM" P-osterior capsule opacification, C-ME, O-cular hypertension, G-laucoma, R-etinal detachment, I-OL problems, M-acular degeneration unmasked

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14. SPECIAL SITUATIONS

Intraoperative Floppy Iris Syndrome (IFIS):

• Caused by alpha-1A blockers (tamsulosin most common, used for BPH)
• Triad: billowing iris, iris prolapse through wounds, progressive intraoperative miosis
• Risk persists even if drug stopped; surgeon must be warned preoperatively

Phacolytic Glaucoma (Open angle):

• Hypermature cataract leaks high MW lens proteins
• Proteins clog trabecular meshwork → raised IOP
• Treatment: urgent lens extraction

Phacomorphic Glaucoma (Closed angle):

• Intumescent (swollen) cataract → pupil block → angle closure
• Treatment: urgent lens extraction + glaucoma treatment

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15. QUICK SUMMARY TABLE FOR MCQs

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16. HIGH-YIELD MNEMONICS SUMMARY

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