Makindo Medical Notes

👁️ Chronic Glaucoma (most often Primary Open-Angle Glaucoma, POAG) is a progressive optic neuropathy caused by raised or poorly tolerated intraocular pressure (IOP). 💡 It is the leading cause of irreversible blindness worldwide. Insidious onset = patients often asymptomatic until advanced → “silent thief of sight.”

📖 About

• Definition: Progressive optic neuropathy with optic disc cupping + visual field loss, often associated with raised IOP.
• Epidemiology: Prevalence ↑ with age; affects ~2% of people >40 years, up to 10% >75 years.
• Risk: Major cause of preventable blindness; earlier detection critical.

🧬 Aetiology & Risk Factors

• ↑ IOP due to reduced aqueous humour outflow (trabecular meshwork dysfunction).
• Genetics: family history ↑ risk 4–9×.
• Age >40, especially elderly.
• Ethnicity: African descent → higher risk & earlier onset.
• Myopia, diabetes, hypertension, corticosteroid use.
• Normal-tension glaucoma: optic neuropathy despite IOP ≤21 mmHg.

⚙️ Pathophysiology

• Aqueous humour produced by ciliary body → trabecular meshwork → Schlemm’s canal.
• In POAG, trabecular outflow gradually impaired.
• ↑ IOP damages retinal ganglion cells → optic nerve head cupping → peripheral field loss.
• Progressive, irreversible retinal ganglion cell apoptosis.

🩺 Clinical Features

• Symptoms: Usually none until advanced. Late: peripheral vision loss → tunnel vision. Central vision preserved until end stage.
• Signs:
  • Optic disc cupping (cup:disc ratio >0.7 or asymmetry).
  • Nasal step & arcuate scotoma on perimetry.
  • Raised IOP (>21 mmHg), though not always.
  • Open anterior chamber angle on gonioscopy.

🔎 Investigations

• Tonometry: Measure IOP.
• Ophthalmoscopy: Disc cupping, rim thinning.
• Visual fields (perimetry): Arcuate defects, nasal step, peripheral loss.
• Optical Coherence Tomography (OCT): Retinal nerve fibre layer thinning.
• Gonioscopy: Confirms open angle (to differentiate from angle-closure).

⚡ Management (NICE & international guidelines)

• Lifestyle: Regular follow-up, driving advice, adherence to drops.
• Medical: First-line = prostaglandin analogues (latanoprost, bimatoprost) → ↑ uveoscleral outflow. Alternative/additional: – Beta-blockers (timolol) → ↓ aqueous production. – Carbonic anhydrase inhibitors (dorzolamide). – Alpha-agonists (brimonidine).
• Laser: Selective Laser Trabeculoplasty (SLT) → increasingly first-line in NICE guidelines (2022).
• Surgery: Trabeculectomy (gold standard), drainage devices, MIGS (minimally invasive glaucoma surgery).
• Normal-tension glaucoma: Aim to lower IOP by ≥30% from baseline.

📉 Complications

• Progressive irreversible visual field loss → blindness.
• Falls, accidents due to poor peripheral vision.
• Psychological impact: anxiety, depression.

📝 Teaching Pearls

💡 Exam favourite: POAG = raised IOP + cupped disc + field loss + open angle. – Silent thief: often asymptomatic until late. – Differentiate from acute angle-closure (painful red eye). – SLT is now recommended by NICE as first-line in many patients.

📊 Quick Comparison: Chronic vs Acute Glaucoma

• 🔹 Chronic (POAG): Insidious, painless, bilateral, gradual peripheral loss, disc cupping.
• 🔹 Acute angle-closure: Sudden, painful, red eye, halos, nausea/vomiting, corneal haze, very high IOP.

📚 References

• NICE NG81: Glaucoma Diagnosis and Management (2022)
• European Glaucoma Society Guidelines 5th Ed (2020)
• Kanski’s Clinical Ophthalmology, 9th Ed