In order to keep the tissues of the eyes nourished, fluid constantly moves into and out of the eyes. The fluid also keeps the eyes in the right shape. When this fluid does not find an outlet and gets blocked, it increases pressure inside the eyes. The rising pressure may severely damage the nerve fibre in the light-sensitive retina and optic nerve. It is an alarming situation because the optic nerve carries the visual information from retina to the brain, and therefore, when the damaged nerve is left untreated, it may cause blindness. This disorder is normally a part of ageing process and people above the age of 60 are more affected.

There are four types of glaucoma, out of which two are common and two are rare.
The common types include:
a) Chronic glaucoma
It is a gradual painless deterioration of sight and the build-up of fluid pressure inside the eye takes years to develop. It does not produce symptoms till the eye is damaged severely. Most of the times, loss of vision is the first symptom, so by the time one becomes aware about the problem, it is often too late. However, if detected and treated in its early stages, the disorder can be made less harmful.
b) Acute glaucoma
If the exit of the fluid is blocked suddenly, it immediately increases pressure in the eye and causes rapid loss of vision. If this disorder is suspected, the person should be given medical assistance urgently. When it is not treated promptly, it can cause permanent reduction in vision.

The rare types glaucoma include:
c) Secondary glaucoma
It is a result of an already existing problem like uveitis or retinal vein occlusion. It can also occur because of certain drugs like corticosteroid eye-drops.
d) Congenital glaucoma
It results from an abnormal development of fluid outflow channels in the eye. Such a defect is present right from the birth and may also result in blindness.

If the symptoms suggest that you may have developed glaucoma, you should get treatment immediately to minimise the damage. The eyes are checked with an instrument called tonometer. This instrument measures fluid pressure, and if glaucoma is diagnosed, eye-drops are used first to reduce pressure. However, in certain cases, the outflow of fluid increases after an operation. This also prevents further accumulation of pressure. However, those who fall in the high-risk category should go for an eye check-up at regular intervals. High-risk group includes people with a family history of developing glaucoma and people with a medical condition, which may trigger the problem.

By the age of 60 years, around 60% of men and 40% of women start snoring