Glaucoma

Glaucoma is the name for a group of eye conditions where the optic nerve is damaged at the point it leaves the eye. This nerve carries information from your retina — the light-sensitive layer at the back of the eye — to your brain, where it’s turned into a picture.

Your eye needs a certain amount of pressure to keep its shape and work properly. In some people, the damage is caused by eye pressure being too high. Others have eye pressure within normal limits, but the damage happens because there’s a weakness in the optic nerve itself. In most cases, both factors play a part, to varying degrees. Eye pressure is largely independent of blood pressure, so normal blood pressure doesn’t rule out raised eye pressure.

If the optic nerve comes under too much pressure, it can be injured. Even a lower level of pressure can cause damage — just more slowly, gradually affecting your sight if left untreated.

Chronic glaucoma is by far the most common form. Eye pressure rises very slowly, with no pain to show there’s a problem — but the field of vision gradually becomes impaired. The early loss is usually shaped like an arc, a little above and/or below the centre when looking straight ahead. Left untreated, this blank area spreads outwards and inwards until the centre is last affected, eventually feeling like looking through a long tube — so-called ‘tunnel vision’.

Acute glaucoma is much less common in Western countries. It happens when there’s a sudden rise in eye pressure, which can be painful and will cause permanent damage to your sight if not treated promptly. The affected eye becomes red, sight deteriorates and may even black out, sometimes with nausea and vomiting, and misty rainbow-coloured rings may appear around white lights.

Chronic glaucoma becomes much more common with age. It’s uncommon below 40, but affects around one percent of people over that age, and five percent of people over 65.

If you’re of Afro-Caribbean origin, you’re more at risk of chronic glaucoma, and it may come on earlier and be more severe.

Family history matters too. If you have a close relative with chronic glaucoma, you should have an eye test every year — and it’s worth advising other family members to do the same, especially if they’re over 40. People over 40 with a family history of glaucoma (a parent, child or sibling diagnosed with it) are entitled to a free NHS sight test every year, making regular monitoring easy to access if you’re in this higher-risk group.

Most people can still drive if the loss of visual field is not too advanced. You will need a special test to assess any damage to your peripheral vision against the standards of the Driver and Vehicle Licensing Authority.

Early detection and treatment will usually prevent or slow further damage from glaucoma. Much can be done to help you use your remaining vision as fully as possible — ask us about low vision aids and whether you’re eligible to register as partially sighted or blind.