Primary open-angle glaucoma (POAG) is the most common type of glaucoma resulting from the drainage system becoming blocked with debris. It tends to develop slowly over many years. POAG increases with age, affecting 2.5% of people aged over 40, 4.5% of people aged over 60, and 9.7% of people aged over 80.^3,6,16,17

Primary angle-closure glaucoma (PCAG) occurs when the iris bulges forward towards the cornea, narrowing or blocking the drainage channels. Smaller eyeballs increase the risk as drainage is more restricted. Women are more likely to develop PCAG, as are people of East Asian ancestry, and risk also increases with age. It occurs more often in longer-sighted people.^6,16,18

Affecting 0.3-0.5% of adults, PCAG is less common than POAG in the UK but carries a greater risk of vision damage. It can occur abruptly, usually in one eye, with severe pain and rapidly advancing vision loss, as the eye reddens. Pain may be so intense it causes nausea and vomiting. This acute angle closure crisis requires emergency medical treatment. Chronic angle closure glaucoma develops more gradually.^16,17,18