Known as the silent blinding disease, Glaucoma is the second most common cause for blindness globally accounting for almost eight per cent of blindness cases.
In India, glaucoma is the main cause for permanent blindness leaving at least 12 million people affected and more than one million people totally blind. Unfortunately, more than 90 per cent of glaucoma cases remain undiagnosed in the community.
Glaucoma is actually an eye disease that causes damage of the optic nerve progressively and at the point where the nerve leaves the eye to carry visual information to the brain. It occurs due to a fluid build up (pressure) within the eye that causes damage to the optic nerve. The eye makes a fluid called aqueous humour and as new aqueous flows into the eye, the same amount should get drained out. This is called the intraocular pressure that keeps the vision intact.
If the pressure continues to build up, the optic nerve and other parts of the eye will be damaged resulting in vision loss. As the optic nerve fibres get affected, the person may develop blind spots in the eye and ultimately become blind.
There are many types of glaucoma:
Primary open angle glaucoma: This is the most common type of glaucoma and occurs when the eye does not drain fluid normally. Consequently, there is an eye pressure build-up and damage the optic nerve. Unfortunately, this kind of glaucoma does not give any indication before and is also painless. The only option is to get regular check-ups done to detect early damage. Also, some people are sensitive to even normal eye pressure and they are susceptible to getting glaucoma.
Angle-closure glaucoma: When a person’s iris is very close to the drainage angle in the eye, the iris itself blocks the draining and can cause damage. This is usually an emergency attack because there are no symptoms at first. This requires immediate medical care failing which can lead to blindness. But this condition gives some symptoms, unlike primary open-angle glaucoma. Some of the symptoms are blurred vision, eye pain, headache, nausea and seeing halos around lights.
Normal tension glaucoma: This is the third type where people with normal eye pressure also develop blind spots and blurred vision.
There are people that have higher than normal eye pressure and are called as glaucoma suspects. They have a higher risk of developing glaucoma and so should be monitored regularly.
Congenital glaucoma: This occurs due to increased eye pressure in young children. The cause is usually a genetic disorder.
Glaucoma can be diagnosed only with a complete eye examination that involves measuring eye pressure, examining the eye drainage angle, studying the optic nerve and the damage done to it and measuring the thickness of the cornea.
The usual treatment for glaucoma is the daily use of eye drops which will lower the eye pressure. It can be done through two ways: either by reducing the amount of aqueous fluid in the eye or by helping the eye drain the fluid better. There are two main types of laser surgery to treat glaucoma. They help aqueous drain from the eye.
There are special surgical procedures too to treat glaucoma:
Trabeculoplasty: This is for people who suffer from open-angle glaucoma. A laser is used to make the drainage angle free from fluids and so the eye pressure is reduced.
Iridotomy: This procedure is for people who suffer from angle-closure glaucoma. The surgeon makes a tiny hole in the iris so that the fluid flow is normal.
There is another more complex surgery where the surgeon creates a new draining channel for the fluid so that pressure is normalised. Sometimes the surgeon uses a glaucoma drainage tube in the eye that sends the fluid to a collection area which is then absorbed into the blood vessels directly.
The writer is a Consultant – Opthalmology, Columbia Asia Hospital
Dr Poonam Yadav