Glaucoma explained: the silent thief of sight

What glaucoma is

Glaucoma is damage to the optic nerve — the cable that carries pictures from the eye to the brain. In most cases this damage is linked to the pressure inside the eye being too high for that particular nerve to cope with. The eye constantly makes a clear fluid that drains away through a mesh at the front; if drainage is sluggish, pressure builds up and slowly harms the nerve fibres. Because the nerve damage begins at the edges of your vision, you do not notice the early loss — the brain fills in the gaps. Over years, untreated glaucoma narrows vision from the sides inwards, which is why it can go unnoticed until it is advanced.

The main types

The most common form is primary open-angle glaucoma, which develops slowly and painlessly over years — this is the classic silent type. A much rarer but dramatic form is acute angle-closure glaucoma, where drainage suddenly blocks and pressure rises fast, causing a painful red eye, blurred vision, haloes around lights, headache and vomiting; this is an emergency needing immediate eye care. Some people develop optic nerve damage even with normal pressure (normal-tension glaucoma), and others have raised pressure without damage yet (ocular hypertension), which is monitored. Certain people are at higher risk: older age, a family history of glaucoma, African-Caribbean heritage, short-sightedness and diabetes all raise the chance.

How it is found

Because open-angle glaucoma causes no symptoms early on, it is usually picked up at a routine eye test rather than because someone notices a problem. This is the single most important message about glaucoma: regular sight tests save sight. During an eye examination, the optometrist measures the pressure inside your eye, examines the optic nerve at the back, and checks your field of vision to look for gaps at the edges. In the UK, eye tests are free on the NHS for people over 60, and for those over 40 with a close relative who has glaucoma, among other groups. If glaucoma is suspected, you are referred to a hospital eye service for confirmation and a treatment plan.

How it is treated

The goal of treatment is to lower the pressure inside the eye to a level that stops the nerve damage getting worse. Sight already lost cannot be brought back, but further loss can usually be prevented. For many people, the first treatment is a course of eye drops used every day to reduce pressure, and taking them reliably is essential because glaucoma is a long-term condition. Laser treatment to improve drainage is increasingly offered early and can reduce the need for drops. If drops and laser are not enough, surgery can create a new drainage route. Treatment is tailored to the type and severity, and lifelong monitoring checks that pressure and the visual field stay stable.

Living with glaucoma

A diagnosis of glaucoma is not a sentence of blindness — most people who are diagnosed and treated keep useful vision for the rest of their lives. The key is early detection and sticking with treatment, even though you feel no different day to day. Using drops exactly as prescribed, attending follow-up appointments and reporting any new symptoms all protect your sight. Because side vision can be affected, glaucoma can influence driving, and there are legal standards you must meet; your eye team will advise you. Support organisations offer practical help with drops, appointments and adjusting daily life. Encouraging relatives to have their eyes tested is also worthwhile, because glaucoma runs in families.