Glaucoma

Glaucoma is the third biggest cause of blindness worldwide. It affects around 60 million people, of whom about 4.5 million have become blind. It is common in both developed and developing countries.

What is glaucoma?

Glaucoma is when the nerve, known as the optic nerve, that carries images from the eye to the brain is damaged. This is caused by clogged drainage channels within the eye which cause pressure in the eyeball. The result is loss of vision. It develops gradually, and people may not realise they have it. On reaching an advanced stage glaucoma is extremely difficult and expensive to treat.

Glaucoma is often associated with ageing, though it is not confined to the elderly. People with glaucoma in their family history are far more likely to be at risk. It is more prevalent among African and Asian people.

The main types of glaucoma:

• primary open angle glaucoma is the most common glaucoma. It happens when blockages deep in the eye's drainage channels cause the inner pressure of the eye to build because not enough fluid is drained. This causes a gradual loss of vision.
• angle closure glaucoma (or acute or narrow angle glaucoma) is less common, but develops swiftly. It is caused by a build up in fluid - the result of blockages at the entrance to the eye's drainage channels. Symptoms include headaches, eye pain and blurred vision.
• secondary glaucoma is generally caused by eye injury, tumour or advanced cataract. It can also be a side-effect of certain drugs - particularly steroids.
• normal tension glaucoma causes damage to the optic nerve even though there is no notable increase in the pressure of the eyeball. The causes are subject to debate.
• pigmentary glaucoma occurs when pigmentary granules from the iris break up and spread into the fluid of the eyeball. These then block eye drainage channels.

Treatments for glaucoma

In western countries, the key to reducing the incidence of glaucoma is early diagnosis. This is done by ensuring that a glaucoma check is part of a routine eye test. It measures eye pressure using a jet of air, and examines the inner eye for symptoms.

In Asia and Africa, where eye tests are not as common, checking for glaucoma isn't easy. This makes the impact of the disease far greater as it is caught much later on, when it is difficult to treat.

Treating open angle glaucoma is done by lowering the inner-eye pressure through:

• reducing the amount of aqueous humour produced using medication
• increasing the amount drained from the eyeball using surgery or laser treatment.

For closed angle glaucoma, surgery is the only treatment with noticeable benefits.

Medication

Medication normally comes in the form of eye drops, which often need to be administered every day, for life. As with other forms of long-term medication, this can prove difficult in places where 'western' approaches to medication are not common practice. In poor countries, eye drops are also often either not available or very expensive.

Laser treatment

Laser treatment is very costly and provides only a temporary lowering of pressure.

Surgery

Surgery is the prime treatment for glaucoma in the developing world. It involves creating an artificial drainage hole in the eye, allowing the excess aqueous humor to drain from the eyeball. But surgery has its problems - it may fail, and it increases the risk of cataract.