Glaucoma is a major cause of blindness throughout the world. In developed countries it is one of the major causes of untreatable blindness and visual disability.

What is Glaucoma?

Glaucoma is a condition where the pressure within the eye (intraocular pressure or IOP) is enough to cause damage to the optic nerve. This damage occurs at the point at which the nerve passes through the wall of the eye.

The damage to the nerve causes a loss of its function which may be mild, moderate or severe. In its severe forms, glaucoma can cause total blindness.

The eye has a statistically normal range of pressure but this can be elevated from various causes. 

In some cases of glaucoma, damage to the optic nerve can happen even without apparent elevation of the IOP. In these cases it seems that the optic nerve is predisposed or abnormally vulnerable to damage for some reason.

There are three main categories of glaucoma:

1. Open-angle glaucoma - this usually causes a gradual, but sometimes rapid, loss of vision. The filter mechanism in the anterior chamber of the eye has increased internal resistance to the outflow of aqueous humour.
2. Closed-angle glaucoma - onset can be sudden, and can cause painful, rapid loss of vision. It can also be more gradual. Access to the filter mechanism is blocked by an abnormal configuration of the iris.
3. Secondary glaucoma - the progress of this depends on the cause. The filter mechanism is blocked by a variety of mechanisms related to some other disease process within the eye.

Who gets glaucoma?

Glaucoma is a major cause of blindness throughout the world.

In developed countries it is one of the major causes of untreatable blindness and visual disability.

In some Asian countries, closed-angle glaucoma is a major cause of blindness because of a racial predisposition to develop it.

Open-angle glaucoma is more common and more severe in Negro peoples throughout the world.

The commonest form of glaucoma in developed countries is the open-angle form. This is mainly a disease of old people as IOP rises progressively with age. The most severe forms occur in people who develop it at an early age and who are not diagnosed until it has done a lot of damage.

There are also inherited forms of glaucoma and babies can be born with it (congenital glaucoma).

Symptoms of glaucoma

The symptoms of glaucoma are very variable. In early cases of open-angle glaucoma there are usually no symptoms. Testing can sometimes detect a slight loss of sensitivity of the optic nerve.

Even more advanced disease is often symptom-free but when it becomes severe, variable loss of sensitivity and loss of parts of the field of vision are noticed. In advanced disease the field of vision is severely affected, navigation vision is grossly reduced and even central vision can be lost. In extreme forms, all vision can be lost in both eyes.

In closed-angle glaucoma the symptoms may be acute with sudden loss of vision in one or both eyes, pain caused by very high IOP and nausea and vomiting. Closed-angle glaucoma may also have symptoms more like those of open-angle glaucoma.

All forms of glaucoma can cause blindness.

Damage to the optic nerve generally cannot be reversed once it has occurred.

Can glaucoma be prevented?

In most cases glaucoma cannot be prevented, except in the case of secondary glaucoma by preventing the disease which causes the high IOP.

The key to preventing blindness from glaucoma is early diagnosis and treatment because it is usually possible to slow or stop the progress of glaucoma once it has been diagnosed.

People, especially those over the age of 40, should therefore have a regular examination by a skilled eye-health practitioner. This is especially important when there is a family history of glaucoma or if there are symptoms.

In areas where there is a high prevalence of closed-angle glaucoma, people should be screened to identify those at high risk of developing the condition. These people can then have prophylactic laser treatment so that they do not develop sudden elevation in IOP.

Once glaucoma is diagnosed and treatment commenced, lifelong surveillance by a skilled eye-health practitioner is usually needed.

Can glaucoma be treated?

The main principle of treating glaucoma is to lower the IOP to a level where it will not cause further damage to the optic nerve, and keep it there.

This can be done by a variety of means according to the cause of the raised IOP.

For open-angle glaucoma, drops are the mainstay of treatment and modern therapies can usually be instilled just once or twice a day.

Sometimes laser treatment is used. This can be effective for both open- and closed-angle forms although the technical details of treatment differ according to the type of glaucoma.

In acute closed-angle glaucoma, treatment is urgent. It usually consists of a combination of drops, oral medicines and laser treatment, although sometimes urgent surgery is needed.

Surgery can be used in most forms of glaucoma to create a channel to bypass the filter mechanism of the eye.

This is usually an option for more severe cases or in areas of the world where drop treatment is not an option. 

Note: This information is general in nature and is not a substitute for specialist medical advice. Have your eyes checked regularly every two years, even if you have not noticed any symptoms or changes.