What is it?
Glaucoma is a disease which affects the optic nerve and can cause blindness. The optic nerve is the nerve that carries visual signals from your eye to your brain, allowing you to see. If caught early, glaucoma can usually be controlled. However, it often has no symptoms, so you need regular eye examinations to check for it.
Glaucoma usually begins when pressure increases in the aqueous fluid of the eye. This fluid bathes the inside of the eye, unlike the tears, which bathe the outside. When the pressure builds up it can damage the optic nerve. The eye constantly produces aqueous fluid. If the normal drainage of fluid from the eye, via a structure known as the trabecular meshwork, becomes clogged, too much fluid collects in the eye causing an increase in pressure. There are two main kinds of glaucoma: “open-angle” and “closed-angle.”
Open angle glaucoma
This is the most common kind of glaucoma. It occurs slowly as people age. The drainage area of the eye becomes clogged and the pressure increases. This causes gradual loss of peripheral vision. Often the vision loss is not noticed until it is very advanced.
Closed angle glaucoma
This is much less common than open angle glaucoma. It usually comes on quickly when the drainage area in the eye suddenly becomes completely blocked. The eye pressure rises quickly. You may notice blurred vision and rainbow halos around lights as well as pain, redness of the eye and nausea. If not treated right away it can cause blindness.
This can occur in association with a large number of conditions, including uveitis, retinal blood vessel occlusions and trauma.
Risk factors for glaucoma
Elevated eye pressure
Family history of glaucoma
Associated conditions: high blood pressure, diabetes, myopia (short-sightedness)
How is it diagnosed?
The vision loss from glaucoma is very gradual and usually starts with the peripheral vision and then progresses toward the centre. Most people are therefore not aware that they have a problem and the glaucoma is picked up on a routine eye exam. Simple tests can be done to measure the pressure in the eye and look at a magnified image of the optic nerve head. Other tests may be done to reveal loss of vision and damage to the delicate structures of the eye.
What can be done?
It is not possible to restore vision which has been lost, but in most cases the eye pressure can be lowered to prevent further loss of sight. Treatment depends on the type of glaucoma that you have and the response of your eye to medications. In many cases the condition can be managed with eye drops. However, your eye doctor may recommend surgery or laser treatment in some cases. Once the diagnosis of glaucoma is made, the treatment with medication is lifelong, and aims to slow or halt the progression of the disease by keeping the pressure low. It is important to have regular follow-up to check that the eye pressure is satisfactory and to monitor the appearance of the optic nerve and the visual field. Some of the medications used for glaucoma, including eye drops, may have side effects so if you are having trouble taking your medication, you should speak to your doctor about it.