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🎯 GLAUCOMA - Complete Study Guide

"Glaucoma is the silent thief of sight - it slowly steals your vision before you even notice."

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📌 SECTION 1: WHAT IS GLAUCOMA? (Definition)

Glaucoma is a group of conditions sharing a chronic progressive optic neuropathy that results in characteristic damage to the optic nerve head and retinal nerve fibre layer (RNFL). Progressive retinal ganglion cell (RGC) death and visual field loss follow. IOP is the key modifiable factor.

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📌 SECTION 2: AQUEOUS HUMOR DYNAMICS (The "WHY" of Glaucoma)

How aqueous humor is made and drained:

╔══════════════════════════════════════════════════════════════════╗
║           AQUEOUS HUMOR FLOW - NORMAL EYE                       ║
║                                                                  ║
║  Ciliary Body                                                    ║
║  (Produces AH)                                                   ║
║       ↓                                                          ║
║  Posterior Chamber → Pupil → Anterior Chamber                   ║
║                                       ↓                         ║
║                              Trabecular Meshwork (TM)           ║
║                              (Main drainage - 90%)              ║
║                                       ↓                         ║
║                              Schlemm's Canal                    ║
║                                       ↓                         ║
║                              Episcleral Veins → Blood           ║
║                                                                  ║
║  + Uveoscleral outflow (10%) via ciliary body face              ║
╚══════════════════════════════════════════════════════════════════╝

• IOP is highest in the morning, lowest at night
• Formula: IOP = Rate of Aqueous Production / Facility of Outflow
• If drainage is blocked → IOP rises → optic nerve is compressed → nerve fibres die → vision lost

How damage happens at the optic nerve:

High IOP
   ↓
Mechanical compression of optic nerve axons at lamina cribrosa
   +
Reduced blood flow to optic nerve head (ischaemia)
   ↓
Retinal Ganglion Cell (RGC) death
   ↓
RNFL thinning + Optic disc cupping
   ↓
Visual field defects (peripheral first → tunnel vision → blindness)

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📌 SECTION 3: CLASSIFICATION OF GLAUCOMA

                        GLAUCOMA
                           │
          ┌────────────────┴─────────────────┐
        PRIMARY                          SECONDARY
     (no other cause)              (another disease causes it)
          │
    ┌─────┴──────┐
 Open Angle   Angle Closure
    │              │
   POAG           PACG
   (most            (pupillary block
   common            common cause)
   worldwide)
          │
    ┌─────┴──────┐
  Acute PACG   Chronic PACG
  (emergency!)  (gradual)

Also:
• Normal-Tension Glaucoma (NTG) - IOP normal but nerve damaged
• Ocular Hypertension (OHT) - IOP high but no nerve damage (yet)
• Congenital/Developmental Glaucoma

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📌 SECTION 4: PRIMARY OPEN-ANGLE GLAUCOMA (POAG)

The Most Common Type - "The Silent Thief"

• Adult onset, chronic, bilateral (usually asymmetric)
• Anterior chamber angle is OPEN
• No known cause (primary)
• Asymptomatic until late - patient loses peripheral vision first

Risk Factors:

POAG Pathophysiology:

Trabecular meshwork dysfunction (increased resistance)
         ↓
Aqueous can't drain properly despite OPEN angle
         ↓
IOP rises
         ↓
Optic nerve head damage (cupping of disc)
         ↓
Loss of RNFL → Visual field defects
         ↓
Starts peripherally → concentric narrowing → tunnel vision → blindness

The Optic Disc in Glaucoma:

Visual Field Defects in Glaucoma (MCQ Favourite!):

Progression of visual field loss in glaucoma:

1. Baring of blind spot (early)
2. Paracentral scotoma (small blind patch near centre)
3. Arcuate scotoma (Bjerrum scotoma) - follows nerve fibre layer arc
4. Nasal step (defect crosses horizontal midline nasally)
5. Ring/annular scotoma (double arcuate)
6. Tunnel vision (only central island left)
7. Total blindness

• 24-2 pattern: Standard for glaucoma (24° temporal, 30° nasal)
• 10-2 pattern: For advanced glaucoma with central field threat

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📌 SECTION 5: NORMAL-TENSION GLAUCOMA (NTG)

• The optic nerve is hypersensitive to normal pressure
• Vascular insufficiency / ischaemia plays a big role
• Associated with nocturnal hypotension, vasospasm, migraines, Raynaud's

• Flammer syndrome (vasospasm)
• Sleep apnea
• Systemic hypotension (especially nocturnal dips)
• Helicobacter pylori infection

Refer for neuroimaging if:
• VA loss out of proportion to cupping
• Color vision loss (Ishihara)
• Rapid progression despite normal IOP
• Optic disc pallor (pale NRR) → suggests compressive/ischaemic lesion
• Visual field defect not matching RNFL pattern

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📌 SECTION 6: PRIMARY ANGLE-CLOSURE GLAUCOMA (PACG)

"The Dramatic Emergency of Glaucoma"

• Short (hypermetropic) eyes with shallow anterior chambers
• Asian populations (especially East and South Asian)
• Women > Men (2:1)
• Mean age: ~62 years

Mechanism - Pupillary Block (most common):

Hypermetropic (short) eye
        ↓
Shallow anterior chamber + anteriorly positioned lens
        ↓
Lens presses on iris → blocks aqueous flow through pupil
        ↓
Aqueous builds up in POSTERIOR chamber
        ↓
Pushes iris forward (iris bombe)
        ↓
Peripheral iris touches trabecular meshwork
        ↓
ANGLE CLOSES → IOP shoots up acutely

Types of PACG:

Clinical Features of Acute PACG (Exam Favourite!):

• Sudden, severe unilateral eye pain
• Blurred vision + coloured halos around lights (like a rainbow around a streetlight - due to corneal oedema)
• Headache
• Nausea and vomiting (so severe it can mimic an abdominal emergency!)
• The attack is often precipitated by:
  • Sitting in a dark room (pupil dilates → angle narrows)
  • Emotional stress
  • Anticholinergic drugs, topiramate, sympathomimetics

• Eye is red (circumcorneal ciliary injection)
• Cornea is hazy/steamy (oedematous)
• Semi-dilated, fixed pupil (oval, mid-dilated, 4-6 mm) - KEY SIGN
• Shallow anterior chamber
• Very high IOP (sometimes >60 mmHg!)
• Tender eyeball

Precipitating Drugs to Remember (MCQ):

AVOID these drugs in narrow angle glaucoma:
• Anticholinergics (atropine, hyoscine, tricyclic antidepressants)
• Sympathomimetics (adrenaline, decongestants, phenylephrine)
• Topiramate (causes ciliary body swelling → anterior rotation of lens)
• Sulfa drugs

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📌 SECTION 7: GONIOSCOPY (The Essential Examination)

Schwalbe's line (anterior border of TM)
    ↓
Trabecular meshwork (TM) - where aqueous drains
    ↓
Scleral spur (whitish ridge)
    ↓
Ciliary body band (brownish)
    ↓
Iris root

Shaffer Grading System (Angle Width):

MCQ tip: Grade 0 and 1 are at risk of closure. Grade 3 and 4 are safe.

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📌 SECTION 8: INVESTIGATIONS

GLAUCOMA WORKUP FLOWCHART

Patient suspected of Glaucoma
            │
     ┌──────┴───────┐
     │  HISTORY     │ (symptoms, family history, medications, risk factors)
     └──────┬───────┘
            ↓
     ┌──────┴───────┐
     │  TONOMETRY   │ IOP measurement
     │              │ • Goldmann Applanation Tonometry (Gold Standard)
     └──────┬───────┘ • Non-contact (air puff) - screening only
            ↓
     ┌──────┴───────┐
     │  GONIOSCOPY  │ Classify: Open angle vs Closed angle
     └──────┬───────┘
            ↓
     ┌──────┴───────┐
     │  FUNDOSCOPY  │ Optic disc assessment
     │              │ • C/D ratio, NRR, ISNT rule
     │              │ • Disc haemorrhages
     └──────┬───────┘
            ↓
     ┌──────┴───────┐
     │  PERIMETRY   │ Visual field testing
     │ (Humphrey)   │ • 24-2 or 30-2 standard
     └──────┬───────┘ • 10-2 for advanced
            ↓
     ┌──────┴───────┐
     │  OCT         │ Structural imaging
     │              │ • RNFL thickness map
     │              │ • Ganglion Cell Layer analysis
     │              │ • Optic disc parameters
     └──────┬───────┘
            ↓
     ┌──────┴───────┐
     │  PACHYMETRY  │ Central Corneal Thickness (CCT)
     │              │ • Thin cornea = underestimated IOP + more risk
     │              │ • Thick cornea = overestimated IOP
     └──────────────┘

Goldmann Applanation Tonometry (GAT):

• Gold standard for IOP measurement
• Principle: force required to flatten a fixed area (3.06 mm diameter) of cornea
• Correction for CCT: Thin cornea (CCT <555 µm) → add correction (IOP underestimated); Thick cornea → subtract

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📌 SECTION 9: SECONDARY GLAUCOMAS (Quick Reference)

Open-Angle Secondary Glaucomas:

Closed-Angle Secondary Glaucomas:

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📌 SECTION 10: CONGENITAL GLAUCOMA (Primary)

  ┌─────────────────────────────┐
  │  1. EPIPHORA (watering)     │
  │  2. PHOTOPHOBIA             │  ← "3 Ps" in infants
  │  3. BLEPHAROSPASM           │
  │     (squeezing eyelids)     │
  └─────────────────────────────┘

• Corneal diameter >12 mm in a neonate = abnormal
• Haab's striae = horizontal breaks in Descemet's membrane from corneal stretching

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📌 SECTION 11: MEDICAL TREATMENT

Mechanism and Examples:

TARGET: REDUCE IOP by either ↓ Aqueous Production OR ↑ Aqueous Outflow

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📌 SECTION 12: LASER TREATMENT

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📌 SECTION 13: SURGICAL TREATMENT

Trabeculectomy (Filtering Surgery) - Gold Standard

What happens in trabeculectomy:
  
  Conjunctiva flap lifted
         ↓
  Partial thickness scleral flap made
         ↓
  Small block of trabecular tissue removed
         ↓
  Creates a new drainage pathway
         ↓
  Aqueous flows under conjunctival flap
         ↓
  Forms a "bleb" (blister) under conjunctiva
         ↓
  IOP controlled

• Mitomycin C (MMC) - more potent, used in high-risk cases
• 5-Fluorouracil (5-FU) - less potent

• Hypotony (IOP too low) → maculopathy
• Bleb-related infection (blebitis, endophthalmitis) - risk persists for life
• Cataract formation
• Flat anterior chamber

Other Surgical Options:

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📌 SECTION 14: MANAGEMENT OF ACUTE ANGLE CLOSURE - EMERGENCY PROTOCOL

ACUTE ANGLE CLOSURE ATTACK - EMERGENCY MANAGEMENT

IMMEDIATE MEASURES:
  1. Lay patient SUPINE (gravity pulls lens back)
  2. IV Acetazolamide 500 mg (↓ aqueous production rapidly)
  3. Topical Timolol 0.5% (↓ production)
  4. Topical Brimonidine 0.15% (↓ production)
  5. Topical Pilocarpine 2% (constricts pupil, pulls iris away from angle)
     ⚠️ Pilocarpine is less effective when IOP is very high
  6. IV Mannitol 1-2 g/kg (osmotic agent, reduces vitreous volume)
  7. Oral/IV analgesics, antiemetics
  
  Once IOP controlled:
  8. Laser Peripheral Iridotomy (LPI) - DEFINITIVE TREATMENT
     (+ prophylactic LPI to the other eye)

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📌 SECTION 15: TARGET IOP CONCEPT

Setting Target IOP:
  
  Severe damage + high baseline IOP → lower target (e.g., <12 mmHg)
  Mild damage + young patient → more aggressive (e.g., <15 mmHg)
  Advanced Glaucoma Intervention Study (AGIS):
  → IOP consistently <18 mmHg = minimal progression risk
  
  Initial reasonable goal = IOP < 18 mmHg
  
  Progression despite target → lower target further OR consider surgery

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📌 SECTION 16: SPECIAL SECONDARY GLAUCOMAS TO KNOW

Pseudoexfoliation Syndrome + Glaucoma

• White flaky material deposits on anterior lens capsule (classic "bull's eye" pattern), corneal endothelium, iris
• Causes: Weak zonules → lens subluxation; raised IOP → glaucoma
• Most common secondary open-angle glaucoma worldwide
• Responds poorly to medical treatment; often needs surgery early

Pigment Dispersion Syndrome (PDS) + Pigmentary Glaucoma

• Pigment rubs off iris by lens zonules → goes into aqueous → clogs TM
• Classic features:
  • Krukenberg spindle (vertical brown spindle on cornea)
  • Radial spoke-like iris transillumination defects
  • Dense band of trabecular hyperpigmentation
• Typically: Young, myopic males
• Exercise can precipitate pigment dispersion attacks
• Treatment: Laser iridotomy, prostaglandins, miotics (poorly tolerated)

Neovascular Glaucoma (NVG)

• New blood vessels grow over the angle (rubeosis iridis) from ischaemic retinal disease
• Causes: Diabetic retinopathy, CRVO (central retinal vein occlusion), carotid occlusive disease
• Treatment: Anti-VEGF injections + panretinal photocoagulation (treat cause); GDD surgery

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📌 SECTION 17: MASTER COMPARISON TABLE - POAG vs PACG

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📌 SECTION 18: KEY CLINICAL TRIALS TO KNOW (MCQ Exam)

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📌 SECTION 19: QUICK-FIRE MCQ MEMORY TRICKS

🧠 MNEMONICS & MEMORY AIDS

1. ISNT RULE - Normal rim thickness:
   "I Saw Numerous Things"
   Inferior > Superior > Nasal > Temporal

2. Congenital glaucoma signs:
   "3 Bs" = Buphthalmos, Buphthalmos... no wait:
   "3 EBs" = Epiphora, Blepharospasm, photophoBia

3. Drugs to AVOID in angle-closure:
   "ACE" = Anticholinergics, Cycloplegics, Epinephrine/sympathomimetics
   (Also: topiramate!)

4. Gonioscopy mnemonic (structures in angle, front to back):
   "Silly Teachers Should Come In"
   Schwalbe's line, TM, Scleral spur, Ciliary body, Iris

5. Prostaglandin side effects:
   "PIER" = Pigmentation (iris), Increased lashes, Eye redness, pRetinal oedema (rare)

6. Trabeculectomy antimetabolites:
   "MMC > 5-FU" (MMC = Mitomycin C is more potent)

7. Layers damaged in glaucoma:
   Retinal Ganglion Cells → their axons = RNFL
   "RGC axons are the RNFL, RNFL loss = disc cupping"

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📌 SECTION 20: COMPLETE SUMMARY TABLE

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📌 SECTION 21: FLOWCHART - CLINICAL APPROACH TO A GLAUCOMA PATIENT

Patient with suspected glaucoma
             │
    Measure IOP (Goldmann Applanation)
             │
    ┌────────┴─────────┐
  IOP > 21          IOP ≤ 21
    │                   │
    ↓                   ↓
  Gonioscopy        Suspect NTG
    │               (if optic disc damaged)
    │
  ┌─┴──────────┐
Open           Closed
  │               │
POAG or        PACG or
Secondary      Secondary
  OAG           CAG
  │               │
  ↓               ↓
Optic disc    Acute attack?
assessment     │         │
  │           YES        NO
Perimetry      │         │
  │           Emergency  LPI
OCT            Rx        prophylaxis
  │
Target IOP?
  │
Medical → Laser → Surgery

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📌 EXAM TIPS - What Examiners Love to Ask

1. "Most common cause of blindness worldwide" → Cataract (#1); Glaucoma (#2)
2. "Gold standard for IOP measurement" → Goldmann Applanation Tonometry
3. "First sign of glaucoma" → RNFL loss (before visual field loss!) / Paracentral scotoma on perimetry
4. "Semi-dilated, fixed, oval pupil + painful red eye + steamy cornea" → Acute angle closure EMERGENCY
5. "First line drug for POAG" → Prostaglandin analogue (once daily at night)
6. "Beta-blockers are contraindicated in" → Asthma, COPD, Heart block
7. "Krukenberg spindle + spoke iris defects + young myope" → Pigmentary glaucoma
8. "White flakes on lens + raised IOP" → Pseudoexfoliation glaucoma
9. "Goniotomy/trabeculotomy" → Treatment of congenital glaucoma
10. "Pilocarpine mechanism" → Contracts ciliary muscle → opens TM spaces → increases outflow
11. "Malignant glaucoma worsens with" → Miotics (pilocarpine makes it worse!)
12. "Sturge-Weber + glaucoma" → Occurs in 30% ipsilateral to facial haemangioma

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