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Aqueous Humour - Production, Passage, and Drainage

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1. Production (Formation)

Active Secretion (2/3 of total)

1. Sodium ions are actively transported into the intercellular spaces of the ciliary epithelium
2. Chloride and bicarbonate ions passively follow sodium to maintain electrical neutrality
3. This ionic gradient drives osmosis of water from the underlying capillaries into those spaces, which then washes into the posterior chamber

Passive Filtration (1/3 of total)

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2. Passage (Circulation)

• Provides nutrition to avascular structures (lens, corneal endothelium)
• Maintains intraocular pressure (IOP)

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3. Drainage Pathways

Primary (Conventional) Pathway - 80-95% of outflow

1. Aqueous flows into the trabecular meshwork (a cobweb-like porous structure at the iridocorneal angle, also called the Spaces of Fontana)
2. Passes through the trabecular spaces into the canal of Schlemm - a thin-walled, circumferential vein that runs 360° around the eye. Its endothelium is highly porous, permitting even large protein molecules and particles up to the size of red blood cells to pass through. It normally contains only aqueous (not blood)
3. From Schlemm's canal, fluid drains into aqueous veins (small veins that carry only aqueous) and then into episcleral veins
4. Ultimately drains into the superior vena cava and right atrium

Clinical implication: Obstruction of venous return at any point from the eye to the right heart can impede aqueous drainage and raise IOP.

Secondary (Uveoscleral) Pathway - 5-20% of outflow

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4. Intraocular Pressure (IOP)

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5. Summary Flowchart

Ciliary processes (active secretion + iris filtration)
           ↓
    POSTERIOR CHAMBER
           ↓
    Pupillary aperture
           ↓
    ANTERIOR CHAMBER
    (bathes lens + corneal endothelium)
           ↓
    Iridocorneal angle
           ↓
  ┌────────────────────────────┐
  │                            │
Trabecular meshwork       Uveoscleral route
(80-95%)                  (5-20%)
  ↓                            ↓
Canal of Schlemm          Suprachoroidal space
  ↓                            ↓
Aqueous veins             Choroidal vessels
  ↓
Episcleral veins
  ↓
Superior vena cava → Right atrium

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6. Clinical Relevance - Glaucoma

• Open-angle glaucoma - increased resistance to outflow through an anatomically open trabecular meshwork (most common type in Western populations). Treated by drugs that reduce production (beta-blockers, carbonic anhydrase inhibitors) or increase outflow (prostaglandins, pilocarpine)
• Angle-closure glaucoma - the iris root physically covers the trabecular meshwork. In pupillary block, aqueous cannot pass from the posterior to anterior chamber, causing pressure build-up, forward bowing of the iris (iris bombé), and angle closure. Treated with laser iridotomy or surgical iridectomy to create a new passage
• Neovascular glaucoma - fibrovascular membranes (often from VEGF upregulation in retinal ischemia) grow over the iris and trabecular meshwork, blocking outflow

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• Guyton and Hall Textbook of Medical Physiology, Chapter 50 - The Eye
• Barash, Cullen & Stoelting's Clinical Anesthesia, 9e - Formation and Drainage of Aqueous Humor
• Goodman & Gilman's Pharmacological Basis of Therapeutics - Aqueous Humor Dynamics
• Robbins & Kumar Basic Pathology - Glaucoma
• Bailey and Love's Short Practice of Surgery, 28e - The Globe

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Causes of Loss of Vision

Classification as per Ophthalmology (AK Khurana style)

Note: AK Khurana's Comprehensive Ophthalmology is not directly available in this library. The answer below is structured exactly as Khurana classifies it - by onset (sudden vs gradual) and by pain (painful vs painless) - synthesized from Kanski's Clinical Ophthalmology 10th ed., Wills Eye Manual, Tintinalli's Emergency Medicine, and Bailey & Love's Surgery, all of which follow the same standard ophthalmological classification.

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CLASSIFICATION OF LOSS OF VISION

1. By onset - Sudden vs Gradual
2. By pain - Painful vs Painless

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A. SUDDEN (ACUTE) LOSS OF VISION

I. SUDDEN PAINLESS LOSS OF VISION

II. SUDDEN PAINFUL LOSS OF VISION

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B. GRADUAL (CHRONIC) LOSS OF VISION

I. GRADUAL PAINLESS LOSS OF VISION

II. GRADUAL PAINFUL LOSS OF VISION

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QUICK MEMORY TABLE (AK Khurana Framework)

                    PAINFUL              PAINLESS
                 ┌─────────────────┬──────────────────────┐
    SUDDEN       │ Acute ACG        │ CRAO                 │
    (Acute)      │ Optic neuritis   │ CRVO                 │
                 │ Corneal ulcer    │ Retinal detachment   │
                 │ Uveitis          │ Vitreous haemorrhage │
                 │ Endophthalmitis  │ AION / GCA           │
                 │                 │ Macular pathology    │
                 │                 │ Amaurosis fugax      │
                 ├─────────────────┼──────────────────────┤
    GRADUAL      │ Dry eye/SPK      │ Cataract             │
    (Chronic)    │ Scleritis        │ Open-angle glaucoma  │
                 │ Chronic uveitis  │ Diabetic retinopathy │
                 │ Thyroid eye dis. │ AMD                  │
                 │                 │ Refractive error     │
                 │                 │ Retinitis pigmentosa │
                 └─────────────────┴──────────────────────┘

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CLINICAL APPROACH TO VISUAL LOSS

• APD (afferent pupillary defect) present → retinal or optic nerve pathology (CRAO, CRVO, optic neuritis, retinal detachment)
• Red eye + pain → consider corneal pathology, uveitis, acute ACG
• Fundus not visible → vitreous haemorrhage, dense cataract
• Cherry red spot → CRAO
• "Blood and thunder" fundus → CRVO
• Elderly + temporal headache → Giant cell arteritis (treat with steroids urgently)
• Young female + pain on EOM → Optic neuritis (rule out MS)
• Floaters + flashes + curtain → Retinal detachment (surgical emergency)

Temporal arteritis / Giant cell arteritis deserves special emphasis - it is the most important diagnosis not to miss in elderly patients with sudden visual loss. Immediate high-dose systemic steroids can prevent blindness in the fellow eye. - Bailey & Love's Surgery, 28e

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• Wills Eye Manual - Classification of Decreased Vision (Monocular/Binocular, Acute/Chronic, Painful/Painless)
• Tintinalli's Emergency Medicine - Differential Diagnosis Table for Acute Visual Loss
• Kanski's Clinical Ophthalmology 10th ed. - Retinal vascular occlusions, optic neuropathy
• Bailey and Love's Short Practice of Surgery, 28e - Painless loss of vision
• Roberts & Hedges' Clinical Procedures in Emergency Medicine - Unilateral vision loss

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QUICK MEMORY TABLE - Loss of Vision

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🔴 SUDDEN + PAINFUL

• Acute Angle-Closure Glaucoma
• Optic Neuritis (pain on eye movement)
• Corneal Ulcer / Abrasion
• Acute Uveitis (Iritis)
• Endophthalmitis
• Corneal Hydrops

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🟡 SUDDEN + PAINLESS

• Central Retinal Artery Occlusion (CRAO)
• Central Retinal Vein Occlusion (CRVO)
• Retinal Detachment
• Vitreous Haemorrhage
• Ischaemic Optic Neuropathy (AION)
• Giant Cell Arteritis (Temporal Arteritis)
• Macular Hole / Haemorrhage
• Amaurosis Fugax (transient)
• Hysterical Blindness

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🟠 GRADUAL + PAINFUL

• Dry Eye Syndrome / SPK
• Scleritis
• Chronic Uveitis
• Thyroid Eye Disease
• Subacute Optic Neuritis

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🟢 GRADUAL + PAINLESS

• Cataract (most common reversible cause worldwide)
• Open-Angle Glaucoma
• Diabetic Retinopathy
• Age-Related Macular Degeneration (AMD)
• Refractive Error (most common overall)
• Retinitis Pigmentosa
• Corneal Scar / Opacity
• Optic Atrophy

---

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QUICK MEMORY TABLE - Loss of Vision

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Mydriatic and Miotic Agents - Ophthalmology

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UNDERSTANDING THE BASICS

• Mydriatics = block parasympathetics (anticholinergics) OR stimulate sympathetics (adrenergics)
• Miotics = stimulate parasympathetics (cholinergics) OR block sympathetics

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PART 1 - MYDRIATIC AGENTS

A. Pure Mydriatics (No Cycloplegia)

• Acts on dilator pupillae muscle
• Does NOT paralyse ciliary muscle - no cycloplegia
• Preferred when dilation is needed without cycloplegia
• Contraindicated in angle-closure glaucoma

---

B. Cycloplegic Mydriatics (Mydriasis + Cycloplegia)

Key Points:

• Atropine = longest acting, strongest cycloplegic. Used for refraction in children (especially for squint/amblyopia workup). Now largely replaced by shorter-acting agents for routine dilation
• Tropicamide = most commonly used for routine fundus examination (short duration, quick recovery)
• Cyclopentolate = preferred for refraction in children (complete cycloplegia within 45 min)
• Cycloplegia = paralysis of ciliary muscle → loss of accommodation → used to measure true refractive error

Routine Dilated Exam Regimen (Wills Eye):

• Adults: Phenylephrine 2.5% + Tropicamide 1%
• Children: Above + Cyclopentolate 1-2%
• Neonates/Preterm: Lower concentrations (Phenylephrine 1%, Tropicamide 1%, Cyclopentolate 0.2-0.5%)

Clinical Uses of Cycloplegic Mydriatics:

1. Fundus examination
2. Refraction (especially in children - to eliminate accommodative spasm)
3. Treatment of uveitis - to prevent/break posterior synechiae, relieve ciliary spasm pain
4. Penalisation therapy in amblyopia (atropine to better eye)

---

PART 2 - MIOTIC AGENTS

A. Direct-Acting Miotics (Cholinergic Agonists)

Pilocarpine - Most Important Miotic:

• Acts on sphincter pupillae → miosis
• Acts on ciliary muscle → contraction → opens trabecular meshwork → increased aqueous outflow → reduced IOP
• Onset: minutes; Duration: 4-8 hours
• Drug of choice to reduce IOP emergently in both open-angle and angle-closure glaucoma
• Also used to reverse atropine-induced mydriasis
• Adverse effects: Blurred vision (especially near), night blindness (small pupil), brow ache (ciliary spasm), headache

---

B. Indirect-Acting Miotics (Anticholinesterase Agents)

Echothiophate - Key Points:

• Long-acting anticholinesterase miotic
• Lowers IOP by decreasing resistance to aqueous outflow
• Used in glaucoma refractory to other therapies
• Risk: Prolongs action of succinylcholine (avoid in patients needing general anaesthesia - can cause prolonged apnoea)

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QUICK MEMORY TABLE

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CONTRAINDICATIONS

• Mydriatics are contraindicated in angle-closure glaucoma (dilation blocks trabecular meshwork → precipitates acute attack)
• Echothiophate - avoid before general anaesthesia (prolongs succinylcholine effect)
• Darkly pigmented irides require higher concentrations or repeated dosing for adequate dilation

---

• Wills Eye Manual - Mydriatic and Cycloplegic Agents table
• Lippincott Illustrated Reviews: Pharmacology - Atropine, Pilocarpine
• Goodman & Gilman's Pharmacological Basis of Therapeutics - Ophthalmic pharmacology
• Barash Clinical Anesthesia 9e - Ophthalmic agents

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Causes of Red Eye

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CLASSIFICATION

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A. PAINFUL RED EYE (Serious - Refer Urgently)

1. Acute Angle-Closure Glaucoma

• Severe ocular pain, headache, nausea/vomiting (can mimic acute abdomen)
• Hazy cornea, mid-dilated fixed oval pupil, very hard eye, poor vision
• Halos around lights
• More common in older, hypermetropic (far-sighted) patients and Asian populations
• Emergency - treat with pilocarpine, acetazolamide, mannitol → YAG laser iridotomy

2. Keratitis (Corneal Inflammation)

• Painful, photophobic, watering eye
• Herpes Simplex Keratitis - dendritic (branching) ulcer, seen on fluorescein staining. Treat with aciclovir. Steroid drops strictly contraindicated
• Bacterial Keratitis - corneal ulcer, hypopyon possible. Common in contact lens wearers
• Herpes Zoster Ophthalmicus - shingles of ophthalmic division of CN V; keratitis + uveitis
• Marginal ulceration, foreign body, abrasions

3. Anterior Uveitis (Iritis / Iridocyclitis)

• Deep aching pain, photophobia, visual blurring
• Ciliary (circumcorneal) flush - ring of injection around limbus
• Small/irregular pupil (posterior synechiae - adhesion of iris to lens)
• Keratic precipitates on corneal endothelium
• Cells and flare in anterior chamber on slit-lamp
• Associated with HLA-B27 conditions, sarcoidosis, Behçet's, TB

4. Scleritis

• Deep, severe, boring pain - worst of all red eye causes
• Tender on palpation of globe
• Deep scleral inflammation, may cause scleral thinning
• ~50% have underlying systemic disease (Rheumatoid arthritis most common)
• Treat with systemic NSAIDs or steroids

5. Endophthalmitis

• Severe pain, hypopyon, vitritis
• Usually post-operative or post-traumatic
• Ophthalmic emergency - intravitreal antibiotics

6. Corneal Foreign Body / Abrasion

• Acute onset, foreign body sensation, watering, photophobia
• Fluorescein staining shows epithelial defect

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B. PAINLESS (OR MILDLY UNCOMFORTABLE) RED EYE

1. Conjunctivitis - Most Common Cause of Red Eye

Key: Vision is NOT commonly affected in simple conjunctivitis. Viral conjunctivitis may occasionally cause keratitis.

2. Subconjunctival Haemorrhage

• Bright red, well-defined patch under conjunctiva
• Vision completely normal, minimal discomfort
• Causes: coughing, sneezing, straining, trauma, hypertension, anticoagulants, bleeding disorder
• Resolves spontaneously in 1-2 weeks
• Reassure patient; treat underlying cause

3. Episcleritis

• Mild-moderate discomfort, sectoral redness
• Superficial inflammation of episcleral tissue
• Often idiopathic
• Usually self-limiting; topical NSAIDs help

4. Dry Eye Syndrome

• Burning, grittiness, intermittent redness
• Worse in dry/air-conditioned environments
• Schirmer's test reduced

5. Blepharitis (Lid margin inflammation)

• Lid margin redness, crusting, scaling
• Associated conjunctival redness
• Lid hygiene + topical antibiotics

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QUICK COMPARISON TABLE - Key Differentiators

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MEMORY AID - Causes by Category

Conjunctival causes (most common, least serious)

• Bacterial / Viral / Allergic / Chlamydial Conjunctivitis
• Subconjunctival haemorrhage
• Episcleritis

Corneal causes

• Keratitis (HSV, bacterial, fungal, Acanthamoeba)
• Corneal abrasion / foreign body
• Corneal ulcer

Uveal causes

• Anterior uveitis (iritis)

Scleral causes

• Scleritis

Glaucoma

• Acute angle-closure glaucoma

Lid causes (secondary conjunctival redness)

• Blepharitis
• Entropion (lashes rubbing cornea)
• Ectropion (exposure keratitis)
• Stye (hordeolum) / Chalazion

Systemic / Others

• Dry eye
• Chemical / radiation injury
• Trauma
• Endophthalmitis (post-op/trauma)

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Warning signs requiring immediate referral: Pain + reduced vision + abnormal pupil = serious pathology (uveitis, keratitis, acute ACG). Simple conjunctivitis and subconjunctival haemorrhage are the only self-limiting causes. All others need expert management. - Bailey & Love's Surgery, 28e

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• Bailey and Love's Short Practice of Surgery, 28e - Differential Diagnosis of the Acute Red Eye
• Wills Eye Manual - Red Eye classification
• Tintinalli's Emergency Medicine - Conjunctivitis and Eye Emergencies
• Kanski's Clinical Ophthalmology 10e

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Coloured Halos

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WHAT ARE COLOURED HALOS?

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CAUSES OF COLOURED HALOS

1. Glaucoma (Most Important Cause)

• Raised IOP causes corneal oedema (fluid accumulates in corneal stroma and epithelium)
• The oedematous cornea acts as a diffraction grating → splits white light into spectrum
• Halos appear episodically, especially at night or when IOP rises
• Associated symptoms: severe eye pain, red eye, blurred vision, nausea/vomiting, headache
• Rainbow-coloured halos around lights are a hallmark symptom

2. Cataract

• Opacities in the lens scatter and diffract light
• Halos common at night (nocturnal glare / night halos)
• Typically associated with glare from oncoming headlights while driving
• Halos in cataract tend to be less colourful, more whitish/glare-type
• No pain, gradually progressive

3. Corneal Oedema (Any Cause)

• Any cause of corneal epithelial/stromal oedema produces halos
• e.g., bullous keratopathy, Fuchs endothelial dystrophy, post-surgical corneal oedema

4. Mucus/Discharge on Cornea

• Excessive mucus or discharge coating the cornea temporarily
• Halos disappear on blinking (as discharge clears)
• Seen in conjunctivitis, dry eye

5. After Refractive Surgery (LASIK/PRK)

• Multifocal ablation zones and corneal irregular astigmatism post-surgery
• Common complaint in early post-op period

6. Contact Lens Wear

• Dirty or ill-fitting contact lenses can scatter light and produce halos

7. Physiological

• Seen occasionally in normal eyes, especially in bright light causing pupil constriction around lens periphery (not pathological)

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KEY DIFFERENTIATING POINT

Important: If halos appear WITH pain, redness, and blurred vision - Acute Angle-Closure Glaucoma until proved otherwise. This is an emergency.

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TESTS FOR COLOURED HALOS

1. Halo Perimetry / Halo Test (Fincham's Test)

• The most specific test for distinguishing glaucomatous halos from other causes
• Method: The patient is asked to look at a bright point source of light in a dark room. A stenopaeic slit (narrow slit) is placed before the eye and rotated:
  • In glaucoma: the halo disappears at one position of the slit (because the corneal oedema is responsible and slit eliminates it at one angle) - halo breaks up with stenopaeic slit
  • In cataract: the halo does NOT disappear regardless of slit position (lens opacities disperse light in all directions)

• Slit in front of eye rotated 360°
• Glaucoma: halo is abolished at some position → suggests corneal oedema cause
• Cataract: halo persists in all positions of the slit

2. Tonometry (IOP Measurement)

• Goldmann applanation tonometry - gold standard
• Raised IOP (>21 mmHg, often >40 mmHg in acute ACG) confirms glaucoma
• Done urgently when halos + pain present

3. Slit-Lamp Examination

• Examines cornea for oedema, Descemet's folds, bullae
• Examines anterior chamber depth (shallow = angle-closure risk)
• Examines lens for opacities (cataract)
• Cells and flare (uveitis), keratic precipitates

4. Gonioscopy

• Examines the iridocorneal angle
• Open vs closed angle - differentiates open-angle from angle-closure glaucoma

5. Visual Field Testing (Perimetry)

• Humphrey / Goldmann perimetry
• Detects characteristic field defects in glaucoma (arcuate scotoma, nasal step, tunnel vision)

6. Ophthalmoscopy / Fundus Examination

• Optic disc cupping (cup-disc ratio >0.6 suggests glaucoma)
• Retinal changes

7. Pachymetry

• Measures corneal thickness
• Corneal oedema = increased corneal thickness

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MEMORY SUMMARY

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• Goldman-Cecil Medicine - Halos Around Lights
• Wills Eye Manual - Acute Angle-Closure Glaucoma symptoms
• Textbook of Family Medicine - Angle-Closure Glaucoma
• Histology: Text & Atlas (Junqueira) - Glaucoma clinical correlation
• Kanski's Clinical Ophthalmology 10e

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CATARACT - COMPLETE CASE SHEET

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SECTION 1: HISTORY

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A. PRESENTING COMPLAINTS

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B. HISTORY OF PRESENTING COMPLAINTS

• Onset - sudden or gradual?
  • Significance: Cataract is always gradual and progressive. Sudden onset suggests other pathology (retinal detachment, vitreous haemorrhage, vascular occlusion)
• Progression - slow, moderate, fast?
  • Significance: Nuclear cataract progresses slowly over years. Posterior subcapsular (PSC) progresses faster. Diabetic or steroid cataract can progress rapidly
• One eye or both?
  • Significance: Age-related cataract is usually bilateral but asymmetric. Unilateral cataract in young patient suggests trauma, uveitis, or metabolic cause
• Distance vs. near vision affected?
  • Significance: Nuclear sclerosis causes myopic shift → near vision may actually improve ("second sight of the aged") while distance vision deteriorates. PSC predominantly affects near vision (reading) because pupil constricts for near, exposing the opacity

• Significance: PSC cataract causes severe glare in bright light (the opacity is central, right behind the pupil). Nuclear cataract causes less glare. Cortical cataract causes glare when spokes approach the visual axis

• Significance: Due to prismatic dispersion of light through opacified lens. Also seen in acute ACG (corneal oedema) - must be differentiated. In cataract: painless, chronic, no red eye

• Significance: Specific to early cataract - irregular refractive index zones within the lens create multiple images. When double vision persists on closing the other eye = lens problem
• Note: Binocular diplopia (resolves on closing one eye) = extraocular muscle/neurological cause

• Significance: Nuclear cataract increases refractive index of nucleus → lens becomes more convex → increasing myopia → patient needs stronger minus glasses or can suddenly read without spectacles ("second sight"). This is an early sign of nuclear cataract

• Significance: In dim light, pupil dilates → peripheral cortical spokes/opacities come into the visual axis → blurring

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C. PAST HISTORY

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D. FAMILY HISTORY

• Significance: Hereditary/congenital cataract in relatives. Familial tendency in age-related cataract also exists

E. DRUG HISTORY

• Steroids (topical/systemic/inhaled) → PSC cataract
• Chlorpromazine → anterior subcapsular stellate deposits
• Amiodarone → anterior subcapsular deposits
• Miotics (long-term pilocarpine/echothiophate) → anterior subcapsular cataract
• Allopurinol → nuclear cataract

F. PERSONAL HISTORY

• Occupation: Significance: Glass blowers, furnace workers → heat-induced (infrared) cataract (posterior subcapsular)
• Smoking: associated with nuclear and posterior subcapsular cataract
• Prolonged UV exposure (outdoor workers)

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SECTION 2: GENERAL PHYSICAL EXAMINATION

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SECTION 3: OPHTHALMIC EXAMINATION

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A. VISUAL ACUITY (VA) - Most Important

1. Test each eye separately (cover the other eye with an occluder)
2. Use Snellen's chart at 6 metres in good illumination
3. Ask patient to read smallest line they can
4. Record as 6/6, 6/9, 6/12... down to 6/60
5. If cannot read top letter (6/60): test at 3 metres → record as 3/60
6. If cannot read at 3m: count fingers → "CF" at ___ metres
7. If cannot count fingers: hand movements → "HM"
8. If no HM: light perception → "PL" (test with torch)
9. If no light perception: "NPL"
10. Then test with pinhole: if VA improves with pinhole → refractive error component; if no improvement → suggests media opacity or macular disease

• Establishes baseline VA and surgical indication
• Near VA (N notation, Jaeger chart): PSC and nuclear cataracts affect near/distance differently
• Pinhole test: In cataract, pinhole usually improves VA (reduces scatter from peripheral lens)
• Glare testing: Check VA in bright illumination - in PSC and cortical cataract, VA drops dramatically in bright light (glare disability)

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B. TORCH EXAMINATION (External Eye)

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C. OBLIQUE ILLUMINATION TEST (Torch Test for Cataract)

1. Seat patient in a slightly darkened room
2. Hold torch at 45° to the optical axis from the lateral side
3. Shine light into the eye from the side
4. Look at the lens through the pupil

• Immature cataract: The iris casts a crescent-shaped shadow on the lens (iris shadow) because the opacity has not reached the anterior surface - called "iris shadow present" / positive iris shadow sign
• Mature cataract: Lens is completely opaque, opacity reaches the front - no iris shadow (negative iris shadow)
• Hypermature cataract: Wrinkled capsule, milky/pearly white appearance

• Quick bedside test to roughly stage cataract maturity
• Positive iris shadow = immature (not yet mature)
• Negative iris shadow = mature cataract

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D. DISTANT DIRECT OPHTHALMOSCOPY - RED REFLEX TEST

1. Set ophthalmoscope to +10 dioptre (convex lens, for initial view)
2. Keep at arm's length (~30 cm) from patient
3. Look through the ophthalmoscope in a dimly lit room (pupil slightly dilated)
4. Direct light into the patient's pupil
5. Observe the red reflex (orange-red glow from fundus)

• Normal: Bright orange-red reflex (like red-eye in photographs)
• Cataract: Black/dark opacities against the red reflex
  • Nuclear cataract: central dark shadow
  • Cortical: spoke-like dark shadows at periphery
  • PSC: central dark shadow
• Mature cataract: Absent red reflex (no fundal glow visible)

• Identifies presence and approximate location of lens opacity
• Absent red reflex = mature/dense cataract OR fundal pathology
• Grading: Can roughly estimate density

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E. SLIT LAMP BIOMICROSCOPY - Most Detailed

1. Patient sits at the slit lamp, chin on chin-rest, forehead against bar
2. Align the eye level
3. Start with broad beam, medium magnification
4. Examine in sequence: lids → conjunctiva → cornea → anterior chamber → iris → lens

• Use a narrow beam at 45° to the eye
• Scan from anterior capsule to posterior capsule
• The slit beam shows the layers as bright sections: anterior capsule → anterior cortex → nucleus → posterior cortex → posterior capsule

• Use the fundal red reflex as a backlight
• PSC appears as dark granular opacity against the red background - most sensitive method

• Nuclear Colour (NC): 1-6
• Nuclear Opalescence (NO): 1-6
• Cortical (C): 1-5
• Posterior Subcapsular (P): 1-5

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F. PUPIL REACTIONS

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G. EXTRAOCULAR MOVEMENTS (EOM)

• How: Ask patient to follow your finger in H-pattern
• Significance: Pre-existing strabismus (squint) → amblyopia in that eye → limited visual recovery post-cataract surgery

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H. INTRAOCULAR PRESSURE (IOP)

1. Instil local anaesthetic + fluorescein drops
2. Apply blue cobalt light at slit lamp
3. Place applanation head on cornea
4. Adjust dial until two green semi-circles meet
5. Read IOP from the dial (multiply by 10 → mmHg)

• Raised IOP → glaucoma (may co-exist with cataract)
• Phacomorphic glaucoma - intumescent (swollen) lens pushing iris forward → raised IOP
• Phacolytic glaucoma - protein leaking from hypermature cataract blocking trabecular meshwork → raised IOP
• Low IOP → uveitis, retinal detachment (check for other pathology)

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I. FUNDUS EXAMINATION

• Dilate pupil (Tropicamide 1% + Phenylephrine 2.5%, wait 20-30 min)
• Use direct ophthalmoscope (+2D for normal emmetrope) or slit lamp with +90D/+78D lens
• Examine: disc, vessels, macula, periphery

• Must be done before deciding on surgery
• Optic disc cupping → glaucoma (may limit visual prognosis)
• Macular degeneration, diabetic maculopathy, epiretinal membrane → visual prognosis is limited even after successful cataract surgery
• If fundus not visible due to dense cataract → B-scan ultrasonography to rule out retinal detachment, vitreous haemorrhage, intraocular tumour

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SECTION 4: SPECIAL INVESTIGATIONS (Pre-Surgical Workup)

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SECTION 5: TYPES OF AGE-RELATED CATARACT - Quick Reference

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SECTION 6: DIAGNOSIS STATEMENT

"Mr/Ms _____, aged _____ years, presenting with gradual, painless, progressive diminution of vision in the right/left/both eyes for ___ months, is a case of immature/mature senile cataract of the nuclear/cortical/PSC type in the right/left eye, with no significant co-morbidities, fit for phacoemulsification with IOL implantation under topical/peribulbar/general anaesthesia."

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• Wills Eye Manual - Cataract workup, types, examination
• Goldman-Cecil Medicine - Cataract clinical features
• Pfenninger & Fowler's Procedures for Primary Care - Slit lamp lens examination technique
• Kanski's Clinical Ophthalmology 10e - Cataract classification

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CATARACT - A TO Z (Comprehensive Ophthalmology Notes)

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1. DEFINITION

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2. EPIDEMIOLOGY

• Most common cause of reversible/treatable blindness worldwide
• Accounts for ~47% of global blindness
• Most common cause of blindness in India and developing countries
• Responsible for ~10 million cataract surgeries per year globally
• Prevalence increases with age: ~50% at 65-74 years, nearly 70% above 75 years

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3. ANATOMY OF THE LENS (Essential for Understanding Cataract)

• Crystallins (α, β, γ) = 90% of lens protein - responsible for transparency
• These are long-lived proteins with NO protein turnover → any damage is permanent

• Lens is avascular - nourished entirely by aqueous humour
• Main energy source: anaerobic glycolysis (Embden-Meyerhof pathway)
• Glucose enters via facilitated diffusion; metabolised to sorbitol in diabetics (sorbitol pathway - key in diabetic cataract)
• Na-K ATPase pump maintains ionic balance; failure → water influx → opacification

• Lens contributes ~16-18 dioptres of total eye's refracting power (~60D total)
• Normal refractive index: 1.386 (nucleus) to 1.336 (cortex)

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4. PATHOGENESIS OF CATARACT

1. Protein aggregation - crystallin proteins unfold and aggregate → large protein complexes scatter light
2. Oxidative damage - free radicals (UV, metabolic) damage proteins and lipids → sulphydryl groups oxidise → protein cross-linking
3. Hydration of lens fibres - ionic pump failure → water influx → cortical oedema → vacuoles and clefts
4. Accumulation of sorbitol (diabetics) - aldose reductase converts glucose → sorbitol → osmotic swelling
5. Decreased antioxidant defences - decreased glutathione, ascorbic acid, vitamin E with age

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5. CLASSIFICATION / TYPES OF CATARACT

BY AGE OF ONSET:

• Congenital - present at birth or within first year
• Developmental - develops in childhood/early life
• Senile (Age-related) - most common type, after 50 years
• Presenile - before 50 years due to systemic disease

BY AETIOLOGY:

• Senile/Age-related
• Traumatic
• Complicated (secondary)
• Toxic/Drug-induced
• Metabolic/Systemic
• Radiation
• Congenital

BY MORPHOLOGY (Most Important Clinically):

A. SENILE CATARACT - 4 Stages

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B. BY MORPHOLOGICAL TYPE OF SENILE CATARACT:

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6. AETIOLOGY (Causes)

A. SENILE / AGE-RELATED

• Primary cause: Age → oxidative stress, UV accumulation, protein denaturation
• Risk factors: UV-B exposure, smoking, alcohol, low socioeconomic status, poor nutrition

B. METABOLIC

C. DRUGS / TOXIC

D. PHYSICAL AGENTS

E. TRAUMATIC CATARACT

F. COMPLICATED CATARACT (Secondary to Eye Disease)

• Pattern: typically posterior subcapsular or polychromatic lustre (bread crumb appearance)
• Uveitis → PSC (also from steroid treatment)
• Retinitis pigmentosa → PSC (classic association)
• High myopia → nuclear cataract earlier

G. CONGENITAL CATARACT

• Intrauterine infections: Rubella (most important - "pearly white" nuclear cataract + salt-pepper retinopathy), Toxoplasmosis, CMV, Herpes, Syphilis (TORCHES)
• Hereditary: Autosomal dominant most common
• Metabolic: Galactosaemia (oil drop), Galactokinase deficiency, Lowe syndrome, homocystinuria
• Chromosomal: Down syndrome (trisomy 21), Turner syndrome
• Syndromes: Marfan (subluxated lens), Alport, Nance-Horan

• Zonular/Lamellar - most common type, surrounds nucleus like onion skin
• Polar - anterior or posterior
• Nuclear - embryonic/fetal nucleus
• Total - entire lens
• Sutural - along lens sutures
• Membranous - resorbed cataract leaving membrane

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7. CLINICAL FEATURES

SYMPTOMS:

SIGNS:

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8. COMPLICATIONS OF CATARACT ITSELF (Untreated)

A. PHACOLYTIC GLAUCOMA (Hypermature Cataract)

• Liquefied cortical proteins leak through intact but permeable capsule
• Macrophages engulf proteins → clog trabecular meshwork → open-angle glaucoma
• Presents with: pain, raised IOP, white cornea, white lens, hypopyon may be present
• Aqueous appears "milky" on slit lamp

B. PHACOMORPHIC GLAUCOMA (Intumescent Cataract)

• Swollen (intumescent) lens pushes iris-lens diaphragm forward → narrow anterior chamber → angle-closure glaucoma
• Presents like acute ACG: severe pain, red eye, raised IOP
• Needs urgent cataract surgery after IOP control

C. PHACOANAPHYLAXIS (Lens-Induced Uveitis)

• Immune reaction to leaked lens protein → granulomatous uveitis
• Mutton-fat keratic precipitates, hypopyon, raised IOP

D. SUBLUXATION / DISLOCATION OF LENS

• Weak zonules (Marfan, trauma, hypermature)
• Anterior dislocation → acute ACG
• Posterior dislocation → into vitreous

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9. INVESTIGATIONS / PRE-OPERATIVE WORKUP

Ocular Investigations:

Systemic Pre-op Investigations:

• Blood sugar (fasting + PP) - diabetes
• Blood pressure
• CBC, coagulation profile (PT, INR)
• ECG (for GA cases)
• Urine routine
• HIV, HBsAg (for staff safety)

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10. IOL POWER CALCULATION

• P = IOL power
• A = A-constant (specific to each IOL type, usually 118-119)
• L = axial length in mm
• K = average keratometry reading in dioptres

• A-scan ultrasound (contact or immersion)
• Optical biometry (IOLMaster) - gold standard, non-contact, most accurate

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11. SURGICAL MANAGEMENT

INDICATIONS FOR SURGERY:

• VA ≤6/18 affecting daily activities (driving, reading, occupation)
• Glare/contrast loss affecting quality of life
• Anisometropia causing difficulty with spectacles

• Phacolytic or phacomorphic glaucoma
• Phacoanaphylaxis
• Lens-induced uveitis
• When cataract prevents treatment/monitoring of posterior segment (e.g., diabetic retinopathy, glaucoma)

• Congenital cataract → urgent (prevent amblyopia)

CONTRAINDICATIONS:

• Active corneal/conjunctival infection
• Uncontrolled systemic disease (uncontrolled DM, severe cardiac disease)
• Relative: single eye (extra caution), poor visual potential, patient unable to cooperate

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TYPES OF SURGERY:

A. PHACOEMULSIFICATION (Phaco) - Gold Standard

1. Anaesthesia - Topical (proxymetacaine drops), peribulbar, or subtenon
2. Incision - Clear corneal incision (~2.2-2.8 mm), self-sealing, no sutures needed
3. Viscoelastic injection - fills anterior chamber, protects corneal endothelium
4. Continuous Curvilinear Capsulorhexis (CCC) - circular tear of anterior capsule (~5-5.5 mm)
5. Hydrodissection - saline injected under capsule to free cortex from capsule
6. Hydrodelineation - separates nucleus from epinucleus
7. Phacoemulsification - ultrasonic probe emulsifies and aspirates nucleus
8. Irrigation-Aspiration (I&A) - removes remaining cortex
9. IOL implantation - foldable IOL inserted through small incision into capsular bag
10. Viscoelastic removal
11. Wound hydration / sealing

B. ECCE (Extracapsular Cataract Extraction)

• Larger incision (~10-12 mm)
• Nucleus expressed manually in one piece
• Cortex aspirated
• Non-foldable PMMA IOL implanted
• Sutures required
• Used when hard nucleus (Grade 4+) or phaco not feasible
• Still widely used in developing countries

C. ICCE (Intracapsular Cataract Extraction) - Historical

• Entire lens + capsule removed
• Cryoprobe used to freeze and extract
• No posterior capsule left → cannot place IOL in capsular bag
• Anterior chamber IOL or iris-supported IOL
• Now rarely done (only in subluxated/dislocated lens)

D. SICS (Small Incision Cataract Surgery)

• Modified ECCE with smaller (~6-7 mm) scleral tunnel incision
• Self-sealing valve incision → no sutures
• Cost-effective alternative to phaco in developing countries
• Handles harder nuclei than phaco

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12. ANAESTHESIA FOR CATARACT SURGERY

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13. INTRAOCULAR LENSES (IOL)

• In-the-bag (capsular bag) = ideal, most stable
• Sulcus (in ciliary sulcus, anterior to bag) = when posterior capsule ruptures
• ACIOL (anterior chamber IOL) = when no capsular support
• Iris-claw / Iris-supported = Artisan lens

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14. COMPLICATIONS

INTRAOPERATIVE:

EARLY POST-OPERATIVE:

LATE POST-OPERATIVE:

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15. POSTERIOR CAPSULE OPACIFICATION (PCO) - "After Cataract"

• Most common long-term complication (~30-50% at 5 years without prevention)
• Elschnig's pearls = proliferated lens epithelial cells on posterior capsule
• Soemmering's ring = lens epithelial cells in peripheral capsule bag
• Symptoms: Gradual blurring, glare (same as original cataract)
• Treatment: Nd:YAG laser posterior capsulotomy
  • Outpatient, non-invasive
  • Laser creates a central opening in the posterior capsule
  • Vision improves within 24 hours
  • Risk: Raised IOP (transient), retinal detachment (rare), IOL pitting

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16. CONGENITAL CATARACT - Special Considerations

• Must be treated within weeks of birth for dense/central cataracts
• Visual deprivation during critical period → amblyopia (irreversible if not treated early)
• Unilateral dense congenital cataract: surgery within 6-10 weeks of birth

• Contact lens or glasses for optical correction (IOL not always implanted in very young)
• Amblyopia therapy - patching the better eye to force use of operated eye
• IOL usually implanted after age 2 years

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17. QUICK MEMORY TABLES

Causes of PSC Cataract (Posterior Subcapsular)

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DIFFERENTIATING TYPES OF SENILE CATARACT

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SURGICAL COMPARISON

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18. IMPORTANT EPONYMS IN CATARACT

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19. IMPORTANT ASSOCIATIONS

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20. PREVENTION

• UV protection (sunglasses)
• Antioxidant diet (vitamin C, E, β-carotene)
• Strict diabetes control
• Avoid unnecessary steroid use
• Avoid smoking
• No established pharmacological prophylaxis yet

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• Kanski's Clinical Ophthalmology 10e - Cataract surgery, IOL, indications
• Wills Eye Manual - Cataract types, workup, treatment
• Goldman-Cecil Medicine - Cataract pathophysiology
• Lippincott Illustrated Reviews: Pharmacology - Drug-induced cataract
• Pfenninger & Fowler's Procedures - Slit lamp cataract examination

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Mature vs Hypermature Cataract

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COMPARISON TABLE

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MORGAGNIAN CATARACT (Extreme Hypermature)

• Cortex is completely liquefied and milky white
• Hard brown nucleus sinks to the bottom of the lens bag (due to gravity)
• On examination: upper half appears milky white, lower half shows brown nucleus
• Nucleus moves when head position changes
• Capsule is extremely thin and fragile
• Very high risk of phacolytic glaucoma

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MEMORY SUMMARY

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WHY HYPERMATURE IS MORE DANGEROUS THAN MATURE

1. Phacolytic glaucoma - liquefied lens proteins leak through the capsule, macrophages block the trabecular meshwork → open-angle glaucoma with severe pain
2. Phacoanaphylaxis - immune reaction to leaked lens protein → severe granulomatous uveitis
3. Surgical difficulty - wrinkled thin capsule tears easily during surgery, weak zonules risk lens drop
4. Spontaneous rupture of capsule in very advanced cases

Clinical rule: Mature cataract = operate soon. Hypermature/Morgagnian = operate urgently - risk of irreversible complications rises every day.