Glaucoma: misconceptions galore

Published in The Hindu on March 6, 2008

Cataract may be the most common cause of blindness. Fortunately, symptoms always show up and are easily detected, and surgical intervention can restore vision. Glaucoma, an eye disease that slowly steals vision, is asymptomatic in a majority of the cases and any loss of vision cannot be reversed.

While the awareness of glaucoma is dismal, what is indeed worrying is that the few people who have heard about the disease have some misconceptions.

That increased eye pressure always shows up as a symptom is the biggest misconception. It is to create more awareness and to dispel any misconceptions that March 6 is being celebrated as the World Glaucoma Day.

No symptoms

Those having open angle glaucoma do not have any symptoms and only 1 in 10 Indians with angle closure glaucoma have any symptoms of the disease.

“Not all types of glaucoma present with abnormally high pressure. 60-70 per cent of the people with the disease may have normal pressure at the time of first examination,” said Dr. L. Vijaya, Director, Glaucoma Services at the Sankara Nethralaya Medical Research Foundation, Chennai.

Complicating it further is the fact that eye pressure fluctuation is a common phenomenon even in a normal person. The fluctuation is all the more in the case of those with glaucoma.

Relying on a pressure measurement alone to detect glaucoma is not advisable. “This is more so in those with glaucoma,” said Dr. Ronnie George, Consultant, Glaucoma Services at the Sankara Nethralaya Medical Research Foundation.

Optic disc examination

“Apart from testing pressure, examining the optic disc and nerve fibre layer will help detect glaucoma. We do these regularly,” said Dr. Arulmozhi Varman of Uma Eye Clinic, Chennai.

Additonally, assessing the filtering portion of the eye in Indian and Chinese adults above 40 years is a part of the SE Asia glaucoma interest group guidelines.

Unfortunately, even the loss of peripheral vision, which is the first to be affected and is not a symptom but the result of glaucoma, can fail to alert a person of his disease status.

This is because the loss of vision is a slow process and can go unnoticed till the loss reaches the central field of vision.

Too late

“People don’t realize any vision problem in early and moderate stages of vision loss,” said Dr. George. “In most cases when the patient can notice a vision field restriction, the disease is already in a reasonably advanced stage.”

There is a greater likelihood of a person becoming aware of vision loss if it is in the lower field of vision. For instance, problems while getting down the stairs or reading difficulty is likely to make the person aware of the problem.

The same is not the case with vision loss in the upper field and side vision. That is the insidious nature of glaucoma.

A study done by Dr. Vijaya and her team on 3,924 rural people and 3,850 from Chennai found that 98.5 per cent of the rural population and 94 per cent of the urban population with glaucoma were unaware of their disease.

Medical intervention cannot restore lost vision. It can only arrest further loss of vision.

This makes early detection and timely intervention to minimize the extent of vision loss important.

“If we are able to arrest the disease, even in advanced glaucoma, the person can lead a normal life even with restricted vision,” stressed Dr. Vijaya.

Relieving pressure

Though people may not feel the increased pressure and even simple tests are likely to miss it out, it is the increased pressure that slowly destroys the optic nerve fibres responsible for peripheral vision.

Any increase in eye pressure need not be called glaucoma unless optic nerve damage and vision loss are also seen.

The treatment is therefore aimed at reducing the pressure and preventing any build-up. In the case of open angle glaucoma, medication and regular monitoring are sufficient to control the disease in a majority of the cases.

“Laser is rarely used in India for open angle,” Dr. George said. In the case of angle closure glaucoma, laser along with medication is recommended. Regular check-up is mandatory. Surgery is considered when medical treatment fails.

What is glaucoma?It is a disease of the eye where progressive optic nerve damage causes loss of peripheral vision. Vision loss starts at the periphery and slowly reaches the central field of vision. It is treated by correcting the eye pressure.

A fluid circulates in the front part of the eye between the lens and the cornea. It provides the nourishment for the eye structures. The amount of fluid entering and exiting the eye should be the same. Any imbalance leading to fluid accumulation increases the eye pressure.

The imbalance can be caused by structural changes that narrow down or close the exit point (angle closure glaucoma) or due to the filter at the exit point getting clogged (open angle glaucoma).