glaucoma

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	GLAUCOMA
	*EXPLAINED*

A damaged optic disc

An atrophic optic disc

A normal optic disc

An enlarged optic disc

Advanced glaucoma

A tonometer for eye tension measurement

WHAT IS GLAUCOMA?

Glaucoma is the name given to a group of eye conditions which damage the optic nerve and affects the side vision in a distinctive manner. It is the leading cause of preventable blindness in the UK with about half a million sufferers and accounts for about one in eight of those registered as blind or partially sighted. Over the age of 40 the incidence is about 1-2% and 25% of cases are undiagnosed or not detected until it is too late to prevent some blindness. It is caused by raised eye pressure in most cases or by poor blood flow to the optic nerve. Over 8% of the population over 70 years of age have significantly raised eye pressure and the Afro-Caribbean and Asian population are six times more likely to suffer from glaucoma.

According to the RNIB in 1996 glaucoma accounted for over 11% of those registered as blind or partially sighted.

There are two main types of glaucoma; 1) open angle or chronic glaucoma and 2) closed angle or acute glaucoma.

The most common type by far is open angle glaucoma in which the patient suffers no pain or redness of the eye but the side vision is affected leaving only usable central vision or tunnel vision as the disease progresses, leading to complete blindness if no treatment is provided.

The blindness from the damaged eye may not be noticed as the other eye will be seeing normally. However, a regular eye examination will detect the problem before things are too advanced and once detected, treatment can be implemented to prevent further visual loss.

The second type, acute glaucoma, accounts for less than one tenth of the glaucomas and is accompanied by redness of the eye, pain and blurred vision and must be treated within 48 hours to prevent permanent visual loss.

Treatment for open angle glaucoma is usually in the form of eye drops twice per day, usually Timolol maleate now, although Pilocarpine, two to four times daily, was used for many years. Timolol reduces the production of fluid (aqueous) in the eye but can cause bronchiolar spasm and slow metabolism so it is not used for asthma sufferers or patients with heart problems. More recently newer, more effective, though costly, eye drops have become available. These include the prostaglandin analogues, Latanoprost and Travatan, which increase the outflow of fluid (uveo-scleral outflow) although they change the eye colour and increase eyelash length. Lasers can be used to treat glaucoma. The argon laser trabeculoplasty painless procedure lasts for 15 minutes works well on 80% of the population and the Nd:YAG laser to make a hole in the iris. Marijuana smoking lowers eye pressure but it also reduces blood flow to the optic nerve head.

THE PREVENTION OF GLAUCOMA

The prevention of glaucoma in recent years has become increasingly important and modern techniques can detect the condition at its earliest stage.

PUPIL DILATION

Pupil dilation allows a greater three-dimensional view of the back of your eyes to determine if the optic nerve is pathologically cupped.

VISUAL FIELD ASSESSMENT

Visual field assessment is to determine if your side or peripheral vision is normal. Measuring out to 30 degrees in all directions can detect glaucoma in some people who have normal eye pressure.

CONTRAST SENSITIVITY

Contrast sensitivity is an assessment of your ability to see progressively paler objects and is possible only with the computer-generated vision chart. It has been demonstrated that glaucoma sufferers can have a loss of contrast sensitivity before glaucoma is detectable by any other means.

GONIOSCOPY

Gonioscopy is a technique used to view the angle of the front chamber of the eye to determine if someone is likely to have an acute attack of glaucoma. An acute attack occurs when the pressure suddenly becomes raised and a painful red eye with blurred vision results.

RECENT RESEARCH

TIGHT TIES

According to American researchers the biggest factor governing whether your eye pressure is high is whether your tie is tied too tightly around your neck. Apparently, constriction of the tissues around the neck restricts the flow of blood through the blood vessels that lead to the eye which then causes an increase in measurable eye tension.

WATER

Research has shown that drinking excessive quantities of water within a short space of time can raise eye pressure levels significantly in 80% of glaucoma sufferers. It is recommended to take in fluid in small amounts throughout the day. Large quantities of caffeine have been shown to raise the pressure in the eye for two to three hours so moderate amounts of caffeine are recommended.

EXERCISE

Glaucoma sufferers are advised to get plenty of exercise such as walking and swimming as this may reduce the eye pressure, according to Dr Robert Ritch, medical director of the US Glaucoma Federation. However, he advised against activities necessitating being upside down.

A further benefit of regular energetic exercise is that the blood pressure is better controlled which helps prevent damage to capillaries (small blood vessels). If the glaucoma patient loses weight, the eye pressure is often found to go down, or put another way — the waistline and the eye pressure both benefit from being reduced.