What is Glaucoma?


Glaucoma is the name given to a set of different eye disorders which cause progressively increasing damage to the optic nerve, leading to progressive irreversible loss of visual field. The optic nerve connects and transmits visual signals from the eye to the brain. In most types of glaucoma, the pressure within the eye is higher than normal, and this high pressure directly damages the nerve. Not every eye with high pressures develops glaucoma, however, it is a known risk factor and people with high pressures therefore need regular eye examinations to rule out glaucoma. There is no specific level of eye pressure that definitely causes glaucoma or eliminates the risk of glaucoma. In some cases normal pressures can still lead to glaucoma. Advanced glaucoma can lead to blindness, hence its early diagnosis and treatment is imperative

What is eye pressure?


The cornea and the lens are special parts of the eyeball responsible for focusing and transmitting light. For this purpose they require to be crystal clear. Blood vessels, which normally supply nutrition to cells, are absent from these parts of the eyeball, as they will reduce their clarity. In order to supply nutrition to these sensitive parts, a special liquid, called the aqueous humour is produced in the eye. This liquid bathes the lens and back surface of the cornea, and then drains out of the eye through the ‘trabecular meshwork’, situated in the angle of the eye. When the normal outflow is blocked due to any cause, the pressure in the eye builds up, like a blocked sink. Eye pressures above the normal upper limit of 20 mmHg can lead to optic nerve damage – the mechanism for most types of glaucoma.

Causes of Glaucoma


Glaucoma can occur without any other eye disease being present. This is called Primary glaucoma, and can be of two types – Open angle or Closed angle depending on the status of the drainage angle.
Occasionally, glaucoma can be a complication of other eye diseases. This is then called a Secondary glaucoma, and can occur due to injury, eye inflammation, cataract, advanced diabetes, and use of certain medicines.
Glaucoma can also occur as a congenital entity in newborns, due to abnormal development of the eyeball which does not allow the aqueous fluid to be drained out normally.

How do you know if you have Glaucoma?


Glaucoma being a silent thief of sight, rarely has any symptoms. Very often, patients come to us with complete loss of vision in one eye. Sometimes, in cases of closed-angle glaucoma, patients complain of headaches which are more in the evenings or in the dark. They may also complain of seeing coloured haloes (rainbows) of light when their eye pressure rises. In case of an attack of acute angle closure the patient may complain of severe headache, redness of the eyes, and sudden blurring of vision. This may be associated with nausea and vomiting, and can mimic an abdominal emergency. In India, ange closure accounts for nearly 40% of all cases of glaucoma, and these are the patients who progress to blindness very rapidly. Hence it is very important to diagnose these patients early, and prevent progression of the disease by treating it promptly.
Children with Congenital Glaucoma typically have large eyes, with photophobia and watering. If diagnosed and treated in time these are the eyes where early damage to the optic nerve may be reversed.