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HEALTHWATCH

What glaucome can do: As seen through a normal eye.

Glaucoma is often, though not always, associated with an increase in the eye pressure. This can be because of a mechanical blockage of the circulation of the fluid inside the eyeball (angle closure glaucoma) or due to microscopic damage leading to a resistance to fluid leaving the eye (open angle glaucoma).

Unfortunately, it is often difficult for any glaucoma patient to appreciate any early decrease in the peripheral vision. By the time central vision loss is noticed extensive damage has occurred. Most types of glaucoma do not have symptoms in early stages and it is often referred to as the “silent thief of sight”.

Glaucoma most commonly affects persons above the age of 35 years. The risk of being affected by the disease increases with increasing age and almost 10 per cent of those above the age of 70 years have some form of glaucoma. The risk of having glaucoma is greater in blood relatives of persons with glaucoma. Glaucoma can, rarely, even occur at birth and in children. In these cases the disease is more severe and difficult to treat with medication.

Reduction in peripheral vision.

Glaucoma can also occur because of complications related to eye injuries or eye surgery, diabetic changes in the eye, inflammation (uveitis), blockage of blood vessels in the eye and use of certain medications such as steroids. These types of glaucoma require treatment of the underlying condition as well as the glaucoma.

More than 90 per cent of those with glaucoma in India are undiagnosed. This is partly because the disease is usually asymptomatic and also because any decrease in vision is often attributed to cataract, which is also common in the same age group and not investigated promptly. Glaucoma can be diagnosed early only by undergoing a regular comprehensive eye examination, which includes measuring the eye pressure (intraocular pressure), examining the angle of the eye to look for any obstruction to fluid circulation (gonioscopy), examination of the optic nerve and testing the peripheral vision (if required). Without these tests a large number of glaucoma cases can be missed. Further specialised tests to study the optic nerve may also be advised.

Glaucoma is a lifelong disease that requires treatment once the diagnosis is established. Depending on the type of glaucoma, medication or a laser and medication may be advised as the first step. Though glaucoma is now recognised to be a multi-factorial disease, eye pressure remains the only treatable factor. If the eye pressure is lowered, further damage to the optic nerve is likely to be prevented or delayed. The attempt is to try and reduce the eye pressure with the aim of preserving whatever vision the patient has without compromising the quality of life. Once glaucoma has destroyed optic nerve fibres, no known treatment can reverse the damage.

Eye pressure can be lowered in various ways, such as medicines, laser treatment or surgery.

Medicines for reducing eye pressure in the form of eye drops or tablets. A number of eye drops are available and a drug is prescribed depending on the type of disease, age of the person and other associated diseases. The effect of medication has to be monitored on a regular basis, since the disease can become more severe with time, needing more intensive treatment. Just like high blood pressure, eye pressure needs to be controlled. Therefore, glaucoma can never be “cured” but it needs to be “controlled” to preserve visual function.

Laser treatment for Glaucoma works in three main ways. Laser trabeculoplasty is used in open angle glaucoma. It reduces the resistance to fluid circulation and helps reduce pressure. However, not all persons respond well to this and the reduction in eye pressure after laser treatment often lasts a short time Therefore, laser trabeculoplasty is not commonly performed. Laser Peripheral iridotomy is the definitive treatment of the form of glaucoma that affects half the patients in India. A laser is used to create a hole in the iris. This relieves the mechanical blockage to fluid circulation and facilitates fluid drainage. Laser cyclophotocoagulation is used to destroy parts of the Ciliary body, which reduces the fluid formation inside the eye. This is usually performed in eyes with poor vision since it can have significant complications.

If medications do not control eye pressure or if they create intolerable side effects, surgery may be necessary in a small percentage of people with chronic glaucoma. Glaucoma surgery can be performed alone or in combination with cataract surgery if the person has glaucoma and cataract. An operation called trabeculectomy is an option. This involves creating a channel from just inside the eye so that the fluid can bypass the usual circulation pathway.

Surgery may be advised if medications fail to control the disease, especially in younger people, or if eye pressure is very high. Like medications, surgery is not a permanent cure for the disease since it may not control the eye pressure adequately for a person’s lifetime. Regular monitoring is mandatory after surgery too. As with any other surgery there is a small risk of complications and additional medications or repeat surgery may be required.

Glaucoma is a potentially vision threatening disease. However, those with early and moderate disease often do not notice any restriction in their vision for any of their routine activities. It is possible to preserve vision even in the late stages of the disease with appropriate treatment and careful monitoring. Undergoing comprehensive eye examination on a routine basis is the best way of detecting disease early and preventing potential visual loss.

The writers are from the Glaucoma Society of India.

Anybody over 35 years

Those witha blood relative with glaucoma

Any history of eye injury

Those using steroids for a long time

Check eye pressure

Examine the optic nerve

Examine the angle of the eye (gonioscopy)

Assess peripheral vision (if required)

Frequent changes in spectacle power

Attacks of headache and eye pain associated with a decrease in vision or redness

Difficulty in seeing objects on the side

Decrease in vision

A large eye in an infant

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