Glaucoma: Notes, PPT and PYQs for MBBS

Quick Summary: What You Need to Know for University Exams

• Normal IOP is about 10 to 21 mmHg.
• Main types: primary open-angle (POAG), primary angle-closure (PACG), secondary and congenital (developmental) glaucoma.
• POAG is painless and often unnoticed until late, earning the name "silent thief of sight".
• Acute angle-closure is an emergency with sudden pain, red eye, haloes and a mid-dilated fixed pupil.
• Key investigations: tonometry, gonioscopy, perimetry and optic disc evaluation.
• Prostaglandin analogues are commonly first-line eye drops for POAG; laser peripheral iridotomy treats angle closure.
• Trabeculectomy is the standard filtering surgery.

Glaucoma Across MBBS Subjects

Definition and Classification

Definition: Glaucoma is a chronic, progressive optic neuropathy with characteristic structural changes of the optic nerve head and corresponding visual field defects, commonly associated with raised intraocular pressure.

Classification

POAG Versus Acute Angle-Closure

Aetiology (Risk Factors)

Pathophysiology

Aqueous Humour Dynamics

1. Aqueous humour is produced by the ciliary processes (non-pigmented ciliary epithelium)
2. It flows from the posterior chamber through the pupil into the anterior chamber
3. Most drains through the trabecular meshwork into Schlemm's canal (conventional pathway)
4. The rest drains through the uveoscleral (unconventional) pathway
5. IOP depends on the balance between production and drainage

Mechanism of Damage (Flowchart)

1. Resistance to outflow rises (open angle) or the angle is blocked (angle closure)
2. IOP increases
3. Mechanical stress on the lamina cribrosa and reduced blood flow to the optic nerve head
4. Retinal ganglion cell axons are progressively lost
5. The optic cup enlarges and the neuroretinal rim thins
6. Characteristic visual field defects develop and progress to tunnel vision and blindness if untreated

Angle closure mechanism: In predisposed eyes, the iris is pushed forward against the trabecular meshwork, often because of pupillary block, cutting off drainage and raising IOP sharply.

(Examiner may ask you to draw the aqueous humour pathway and the angle of the anterior chamber.)

Clinical Features

Primary Open-Angle Glaucoma

• Usually no symptoms until advanced
• Frequent change of reading glasses in some patients
• Difficulty with dark adaptation
• Gradual loss of peripheral vision, then tunnel vision

Optic Disc Changes

Visual Field Defects (Typical Progression)

1. Paracentral scotoma
2. Arcuate (Bjerrum) scotoma
3. Nasal step (Roenne)
4. Ring scotoma
5. Tubular vision with a temporal island
6. Complete loss of vision

Acute Angle-Closure Attack

• Sudden, severe eye pain and headache
• Blurred vision with coloured haloes around lights
• Nausea and vomiting
• Red eye with ciliary congestion
• Hazy, oedematous cornea
• Shallow anterior chamber
• Vertically oval, mid-dilated, non-reactive pupil
• Stony hard eye on palpation

Congenital Glaucoma (Buphthalmos)

• Classic triad: photophobia, epiphora (watering) and blepharospasm
• Enlarged, hazy cornea
• Breaks in Descemet's membrane (Haab's striae)

Diagnosis

Management

Principles

1. Lower IOP to a target level that prevents further damage
2. Preserve remaining vision and quality of life
3. Monitor regularly with IOP, disc and field examinations
4. Treat the cause in secondary glaucoma

Antiglaucoma Drugs

Laser Treatment

Surgery

Emergency Management of Acute Angle-Closure (MBBS Level)

1. Lower IOP quickly: intravenous acetazolamide and hyperosmotic agents (such as intravenous mannitol)
2. Topical beta-blocker and alpha agonist
3. Topical corticosteroid to reduce inflammation
4. Pilocarpine once IOP starts to fall
5. Definitive treatment with laser peripheral iridotomy, and prophylactic iridotomy in the other eye

Complications

• Irreversible visual field loss and blindness
• Absolute glaucoma: a painful, blind eye
• Corneal decompensation in chronic high IOP
• Complications of surgery: infection of the filtering bleb, hypotony, cataract

Prevention and Screening (Community Medicine Angle)

• Glaucoma is a leading cause of irreversible blindness worldwide.
• Opportunistic screening of people above 40 years, especially those with a family history, diabetes, myopia or long-term steroid use, helps early detection.
• India's National Programme for Control of Blindness and Visual Impairment (NPCBVI) supports eye care services, including glaucoma detection and management.

Prognosis

Damage already done cannot be reversed, but good IOP control and regular follow-up usually slow or stop further loss. Outcomes are poorest when glaucoma is diagnosed late or when patients stop treatment.

Quick Viva Questions

Q: What is the normal intraocular pressure? A: About 10 to 21 mmHg.

Q: What is the gold-standard instrument for measuring IOP? A: The Goldmann applanation tonometer.

Q: Why is timolol avoided in asthma? A: It is a non-selective beta-blocker and can be absorbed systemically, causing bronchospasm.

Q: What is the classic triad of congenital glaucoma? A: Photophobia, epiphora and blepharospasm.

Q: Why is iridotomy done in the fellow eye after an acute attack? A: The other eye usually has the same narrow-angle anatomy and a high risk of an attack.

How Glaucoma Appears in MBBS University Exams

Typical question styles (not attributed to specific papers or years):

1. "Classify glaucoma. Describe the clinical features and management of primary open-angle glaucoma." (Long essay)
2. "Describe the clinical features and management of acute angle-closure glaucoma." (Long essay)
3. "Write a short note on antiglaucoma drugs." (Short note, Ophthalmology or Pharmacology)
4. "Write a short note on congenital glaucoma." (Short note)
5. "Write a short note on trabeculectomy." (Short note)
6. "Describe the formation and drainage of aqueous humour." (Physiology)

Related Topics

• Cataract
• Retinal Detachment
• Corneal Ulcer
• Diabetes Mellitus
• Hypertension

Related Resources

Ophthalmology hubs and books

• Ophthalmology Hub
• Best Ophthalmology Book for MBBS
• MBBS 3rd Year Hub

Question papers

• Ophthalmology Question Bank
• MBBS 3rd Year Question Papers
• Ophthalmology: RGUHS | KNRUHS | TNMGRMU | NTRUHS | WBUHS | KUHS | RUHS

Frequently Asked Questions