OP7.2 | Primary Open Angle Glaucoma — Summary & Reflection

KEY TAKEAWAYS

Primary open-angle glaucoma (POAG) is the commonest glaucoma type, characterised by a chronically open iridocorneal angle on gonioscopy, progressive optic neuropathy (increasing C:D ratio, neuroretinal rim loss), and corresponding visual field defects (arcuate scotoma, nasal step). The IOP is typically elevated (>21 mmHg, normal = 10–21 mmHg) but in normal-tension glaucoma (NTG) is consistently ≤21 mmHg — demonstrating IOP is a risk factor, not the sole diagnostic criterion. The disease is SILENT — patients are asymptomatic until late, making screening critical. Risk factors include age, family history, Black race, myopia, and thin central cornea. Investigations: Goldmann tonometry, gonioscopy (open angle — definitional), optic disc assessment (ISNT rule, C:D ratio, disc haemorrhages), automated perimetry (Humphrey 30-2), and OCT RNFL. Management: stepwise IOP reduction — prostaglandin analogues (latanoprost — first-line, uveoscleral outflow), beta-blockers (contraindicated in asthma — second-line), CAIs, alpha-2 agonists, SLT (laser first-line alternative), trabeculectomy (surgery — last resort). Lifelong follow-up is mandatory. Critical distinction: POAG (open angle, silent, prostaglandin first-line) vs PACG (closed angle, acute red eye + pain, pilocarpine + acetazolamide emergency → laser iridotomy).

REFLECT

The patient in the hook — a retired schoolteacher with no symptoms — represents millions of people worldwide who have advanced glaucoma without knowing it. He has been told his vision is 'fine' by his brain, which has compensated for his peripheral field loss. Now consider: what screening programme would you design in India to detect POAG earlier in a population of adults over 40? What are the barriers (cost of tonometry and perimetry, trained workforce, follow-up compliance)? And at the individual level — how would you explain to this gentleman why he must use eye drops for the rest of his life, every day, despite feeling no symptoms? The challenge of managing a silent, lifelong condition in an asymptomatic patient is one of the central challenges of chronic disease medicine. How do the principles of patient-centred counselling apply here?