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GLAUCOMA - Complete NEET PG Notes

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1. DEFINITION & OVERVIEW

• Characteristic optic nerve head (ONH) and retinal nerve fibre layer (RNFL) changes
• Progressive retinal ganglion cell (RGC) death
• Visual field (VF) loss

IOP is a key modifiable risk factor - but NOT the defining feature.

⚠️ MCQ TRAP: "Glaucoma is defined by elevated IOP" - FALSE. It is defined by optic neuropathy. Nearly 50% of POAG patients have IOP ≤21 mmHg at any single screening.

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2. AQUEOUS HUMOR DYNAMICS

• Trabecular (conventional) route - 80-90% - pressure-dependent
• Uveoscleral (unconventional) route - 10-20% - pressure-independent

⚠️ MCQ TRAP: Prostaglandins increase IOP reduction via the uveoscleral route (not trabecular).

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3. CLASSIFICATION

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4. PRIMARY OPEN ANGLE GLAUCOMA (POAG)

Epidemiology

• Most common form of glaucoma overall
• 4x more common in African Americans (also 8x more likely to go blind from it)
• Increases with age; insidious onset
• Bilateral, but often asymmetric

Symptoms

• Asymptomatic until late stages (peripheral field loss first, central vision late)
• This is why screening is important

⚠️ MCQ TRAP: "Patient with glaucoma presents with sudden painful loss of vision" = this is ACUTE ANGLE CLOSURE, not POAG. POAG is painless and gradual.

Signs

• IOP: Often elevated BUT may be normal
• Gonioscopy: Open angle, no peripheral anterior synechiae (PAS)
• Optic disc changes:
  • Increased cup-disc ratio (CDR >0.5 suspicious; >0.7 highly suggestive)
  • Asymmetry of CDR between two eyes >0.2 = significant
  • Notching of neuroretinal rim (especially inferior and superior - ISNT rule)
  • Disc hemorrhages (Drance hemorrhage) = sign of active disease
  • RNFL defects on OCT
• Visual field defects (in order of frequency):
  • Bjerrum/arcuate scotoma (most common field defect)
  • Paracentral scotoma
  • Nasal step (Ronne's nasal step)
  • Temporal sector defect
  • Peripheral island + central island (late/tunnel vision)
  • Last to go: central fixation (temporal island is lost before central)

⚠️ MCQ TRAP: The ISNT rule - Neuroretinal rim is normally thickest Inferior > Superior > Nasal > Temporal. Loss starts at inferior or superior pole first.

⚠️ MCQ TRAP: Central vision is relatively preserved until late in glaucoma. Compare with macular degeneration where central vision is lost early.

Visual Field Testing

• 24-2 (or 30-2) pattern: standard glaucoma test
• 10-2 pattern: used for advanced glaucoma to monitor central field more precisely ("split fixation")
• Humphrey field analyzer (HFA) is standard automated perimeter

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5. PRIMARY ANGLE CLOSURE GLAUCOMA (PACG)

Acute Angle Closure Glaucoma (AACG) - HIGH YIELD

• Pupillary block (most common mechanism) - iris apposes lens at pupil → aqueous trapped in posterior chamber → iris bombé → TM obstruction
• Predisposed eyes: Hyperopic eyes (short axial length, shallow AC, thick lens)

⚠️ MCQ TRAP: PACG is more common in females and in East Asians (especially Chinese). POAG is more common in African Americans.

• Mydriatics (topical or systemic anticholinergics - antihistamines, antidepressants, antipsychotics)
• Dim illumination (cinema, watching movies)
• Reading (accommodation)
• Miosis (miotics can rarely precipitate via pupillary block in susceptible eyes)

⚠️ MCQ TRAP: Sympathomimetic mydriatics (phenylephrine) and anticholinergic mydriatics (tropicamide, atropine) can precipitate AACG. Miotics (pilocarpine) are actually used to TREAT AACG.

• Severe ocular pain
• Headache, nausea, vomiting (can mimic acute abdomen)
• Blurred vision + colored halos around lights
• Tearing, photophobia

• IOP markedly elevated (often 40-70 mmHg)
• Circumcorneal (ciliary) injection
• Corneal edema (steamy, microcystic)
• Fixed, mid-dilated pupil (oval, vertically oval, semimydriasis ~4-6 mm)
• Shallow anterior chamber
• Iris bombé (convex iris) - in pupillary block
• Closed angle on gonioscopy

⚠️ MCQ TRAP: Pupil in AACG is mid-dilated and fixed, not fully dilated and not miotic.

• IV Acetazolamide (500 mg bolus) - first line systemic CAI
• Topical timolol (beta-blocker)
• Topical apraclonidine (alpha agonist)
• Topical pilocarpine 2-4% (miotic - pulls iris away from TM) - BUT only effective once IOP starts to fall (ischemic iris won't respond to pilocarpine when IOP very high)
• Topical steroid (to reduce inflammation)
• IV Mannitol (20%, 1-2 g/kg) or glycerol oral - if IOP remains very high

• Definitive treatment (once cornea clears)
• Also performed prophylactically on the fellow eye
• Creates a hole in the iris to bypass pupillary block

⚠️ MCQ TRAP: LPI is the definitive treatment of AACG, not just medical therapy. ⚠️ MCQ TRAP: Prophylactic LPI is done on the fellow eye because it has a similar anatomical predisposition. ⚠️ MCQ TRAP: Pilocarpine alone is NOT the first step - IOP must be lowered first.

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6. NORMAL TENSION GLAUCOMA (NTG) / LOW TENSION GLAUCOMA

• All features of POAG but IOP consistently ≤21 mmHg
• Thought to involve vascular insufficiency of the optic nerve (vasospasm, nocturnal hypotension)
• Associated with Flammer syndrome, migraine, nocturnal hypotension
• Disc hemorrhages more common than in POAG
• Paracentral scotomas closer to fixation point

⚠️ MCQ TRAP: In NTG, rule out other causes of optic neuropathy at "normal" IOP before diagnosing. The treatment is still to reduce IOP further (below 12-15 mmHg).

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7. SECONDARY OPEN-ANGLE GLAUCOMAS

A. Pigmentary Glaucoma

• Young, myopic males
• Pigment from posterior iris rubs off on zonules (Zinn) → pigment floods the angle
• Krukenberg spindle - vertical spindle of pigment on corneal endothelium
• Iris transillumination defects (TIDs) - mid-peripheral, radial, spoke-like (reverse of pseudoexfoliation which has peripupillary TIDs)
• Sampaolesi line: pigment anterior to Schwalbe line on gonioscopy
• Exercise can precipitate acute IOP spikes

⚠️ MCQ TRAP: Krukenberg spindle = pigmentary glaucoma. Sampaolesi line = both pigmentary glaucoma AND pseudoexfoliation.

B. Pseudoexfoliation (PXF) Glaucoma / Exfoliative Glaucoma

• Most common secondary open-angle glaucoma in Europeans
• Grayish-white fibrillar deposits (amyloid-like) on pupillary margin and anterior lens capsule (bull's eye/target pattern - central zone, clear middle zone, peripheral zone)
• Peripupillary TIDs (different from mid-peripheral in pigmentary)
• Sampaolesi line on gonioscopy
• Zonular laxity → risk of lens subluxation/dislocation
• Poor pupil dilation
• IOP often very high and asymmetric (unilateral at presentation more often than POAG)
• More aggressive than POAG; poor response to treatment

⚠️ MCQ TRAP: Pseudoexfoliation has peripupillary TIDs, while pigmentary glaucoma has mid-peripheral/radial TIDs. ⚠️ MCQ TRAP: PXF carries a 25% risk of developing glaucoma. ⚠️ MCQ TRAP: PXF material is NOT true lens exfoliation - true lens capsule exfoliation occurs after heat exposure (e.g., glassblowers). PXF material comes from basement membrane abnormality throughout the body.

C. Steroid-Induced Glaucoma

• Open angle glaucoma with history of steroid use (any route: topical > periocular > intravitreal > oral > inhaled > nasal)
• Onset: 2-4 weeks after starting topical steroids (rarely acute with systemic)
• More potent steroids cause more IOP rise (Dexamethasone > Prednisolone > Fluorometholone > Loteprednol)
• IOP usually normalizes after stopping steroids; but may take months if prolonged use
• Mechanism: reduced outflow via TM pigmented cells

⚠️ MCQ TRAP: Fluorometholone and loteprednol are "soft steroids" with low IOP-raising potential - preferred in patients at risk. ⚠️ MCQ TRAP: Patients most at risk: those with POAG, family history, diabetics, African descent, high myopes, post-trauma.

D. Phacolytic Glaucoma

• Hypermature (Morgagnian) cataract leaks lens proteins through intact capsule
• Macrophages engulf proteins → clog TM → raised IOP
• Open angle
• Iridescent particles (macrophages with engulfed lens material) in AC = pathognomonic
• Severe pain; pseudohypopyon possible
• Treatment: topical anti-glaucoma + definitive cataract extraction

⚠️ MCQ TRAP: Phacolytic = hypermature cataract, open angle, intact capsule, iridescent AC particles. Distinguish from phacomorphic (intumescent cataract, closed angle).

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8. SECONDARY ANGLE-CLOSURE GLAUCOMAS

A. Phacomorphic Glaucoma

• Intumescent (swollen) lens pushes iris forward → closes angle
• Closed angle glaucoma
• Treatment: LPI to relieve pupillary block + cataract extraction (definitive)

⚠️ MCQ TRAP: Phacomorphic = closed angle. Phacolytic = open angle. Both involve lens problems.

B. Neovascular Glaucoma (NVG)

• Causes of retinal ischemia → VEGF release → neovascularization of iris (rubeosis iridis) and angle
• Causes (3 most important): Proliferative Diabetic Retinopathy, CRVO (Central Retinal Vein Occlusion), Ocular Ischemic Syndrome (carotid artery disease)
• Stages:
  • Stage 1: NV at pupillary margin and/or angle, no glaucoma
  • Stage 2: Open-angle NVG (membrane over TM, not yet contracting)
  • Stage 3: Closed-angle NVG (membrane contracts, PAS formation, angle closed)
• Ectropion uveae (eversion of pupillary margin showing pigment epithelium)
• Treatment: Treat underlying cause + anti-VEGF (intravitreal) + IOP control

⚠️ MCQ TRAP: NVG due to CRVO: central retinal vein occlusion. BRVO is less commonly associated. CRAO does NOT typically cause NVG. ⚠️ MCQ TRAP: Most common cause of NVG = Diabetic retinopathy (proliferative DR).

C. Malignant Glaucoma (Aqueous Misdirection Syndrome)

• Aqueous diverted posteriorly into or behind vitreous → pushes lens-iris diaphragm forward → raises IOP
• Flat/shallow AC diffusely (both central and peripheral - unlike pupillary block where central is deeper)
• Occurs typically after glaucoma surgery or cataract surgery in eyes predisposed to PACG
• Treatment:
  • Cycloplegics (atropine) first line - deepens AC
  • Hyperosmotic agents
  • Vitrectomy (definitive)
  • AVOID miotics - worsen the condition

⚠️ MCQ TRAP: In malignant glaucoma, LPI does NOT help (no pupillary block). Atropine (cycloplegic) is the key treatment. ⚠️ MCQ TRAP: Both central and peripheral shallowing distinguishes malignant glaucoma from pupillary block (where peripheral is shallower but central may be preserved).

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9. DEVELOPMENTAL (CONGENITAL) GLAUCOMA

Primary Congenital Glaucoma (Buphthalmos)

• Maldevelopment of the TM and anterior chamber angle
• Inheritance: Autosomal recessive (gene: CYP1B1)
• Presents at birth to 3 years; most by age 1
• Bilateral in 80%

1. Epiphora (excessive tearing)
2. Photophobia
3. Blepharospasm

• Buphthalmos ("ox eye") - enlarged globe due to stretching (sclera is distensible in infants)
• Corneal diameter >12 mm before age 1 (normal = 10 mm at birth, 11 mm by 1 year)
• Haab's striae - horizontal or curvilinear tears in Descemet membrane (due to stretching), with scalloped edges
• Corneal clouding/edema
• Increased CDR
• Axial myopia

⚠️ MCQ TRAP: Haab's striae = horizontal (or curvilinear). Compare with forceps injury = vertical Descemet tears (and typically unilateral with forceps history). ⚠️ MCQ TRAP: Buphthalmos occurs only in infancy because the sclera is distensible. Adults cannot develop buphthalmos. ⚠️ MCQ TRAP: Congenital glaucoma inheritance = AR (not AD).

• Goniotomy (if cornea is clear, preferred) or Trabeculotomy (if cornea is hazy, can't visualize angle) - both are first line
• Trabeculectomy only if above fail
• Medical therapy is temporizing only

⚠️ MCQ TRAP: Treatment of congenital glaucoma is surgical, not medical. Goniotomy when cornea clear; trabeculotomy when cornea opaque.

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10. GLAUCOMA IN PHACOMATOSES

Sturge-Weber Syndrome

• Glaucoma ipsilateral to the facial (port-wine) hemangioma in ~30%
• Mechanism: trabeculodysgenesis (infants) + raised episcleral venous pressure (older patients)
• 60% present before age 2 (buphthalmos)

⚠️ MCQ TRAP: In Sturge-Weber, glaucoma is on the same side as the facial nevus.

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11. PLATEAU IRIS SYNDROME

• Angle closure despite patent LPI
• Due to abnormal anteriorly positioned ciliary processes pushing the peripheral iris against TM
• Treatment: Laser iridoplasty (peripheral) or long-term pilocarpine

⚠️ MCQ TRAP: Acute angle closure that recurs after LPI = Plateau Iris Syndrome (not pupillary block).

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12. ANTI-GLAUCOMA DRUGS - HIGH YIELD PHARMACOLOGY

⚠️ MCQ TRAP: Prostaglandins are given once daily at night (QHS). Beta-blockers usually twice daily. ⚠️ MCQ TRAP: Betaxolol is a selective β1 blocker - relatively safer in asthma (but not entirely safe). ⚠️ MCQ TRAP: Acetazolamide is CI in sickle cell disease (causes sickling crisis by acidosis). Use with caution. ⚠️ MCQ TRAP: Glycerol is metabolized to glucose → contraindicated in diabetics → isosorbide is preferred oral hyperosmotic in diabetics. ⚠️ MCQ TRAP: Brimonidine + MAOIs = hypertensive crisis (absolute CI).

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13. SURGICAL TREATMENT

Laser Procedures

⚠️ MCQ TRAP: Laser trabeculoplasty (ALT/SLT) is CONTRAINDICATED in angle-closure glaucoma.

Filtering Surgery

• Trabeculectomy (guarded filtration procedure) - standard glaucoma surgery
  • Antimetabolites (MMC > 5-FU) used to prevent bleb scarring
  • MMC (Mitomycin C) is more potent but greater risk of hypotony/avascular bleb
• Tube shunts / Drainage implants (Molteno, Baerveldt, Ahmed valve) - for failed trabeculectomy
• MIGS (Minimally Invasive Glaucoma Surgery) - for mild-moderate POAG: iStent, trabectome, canaloplasty, XEN gel stent

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14. HIGH-YIELD VISUAL FIELD DEFECTS IN GLAUCOMA

⚠️ MCQ TRAP: Altitudinal field defect is NOT typical of glaucoma - think AION or branch retinal artery occlusion. Glaucoma causes arcuate defects respecting the horizontal midline in nasal field.

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15. IMPORTANT ASSOCIATIONS / QUICK FACTS

⚠️ MCQ TRAP: Glaucoma is the leading cause of irreversible blindness worldwide. Cataract leads in total blindness but is reversible. ⚠️ MCQ TRAP: Thin cornea (low CCT) is an independent risk factor for glaucoma (also underestimates IOP on applanation).

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16. GONIOSCOPY - MUST KNOW

• Shaffer grading (angle width):
  • Grade 0 = closed
  • Grade 1 = very narrow (<10°) - closure likely
  • Grade 2 = narrow (10-20°) - closure possible
  • Grade 3 = open (20-35°) - closure unlikely
  • Grade 4 = wide open (35-45°) - closure impossible

⚠️ MCQ TRAP: Schwalbe's line is the most anterior landmark (peripheral to TM). A prominent Schwalbe line = Posterior embryotoxon (seen in Axenfeld-Rieger syndrome).

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17. SPECIAL SITUATIONS

• Topical beta-blockers relatively contraindicated (fetal bradycardia)
• Prostaglandins absolutely CI (uterotonic, risk of abortion/premature labor)
• Brimonidine CI in neonates/infants (apnea, hypotension)
• Carbonic anhydrase inhibitors (oral) - teratogenic in animal studies; use with caution
• Safest option: topical beta-blocker with close monitoring (some use dorzolamide)

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18. KEY MCQ TRAPS SUMMARY

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