TYPES OF GLAUCOMA
Glaucoma is the second leading cause of blindness in the world and the leading cause of irreversible blindness. It is a result of an increase in the pressure of the eye (intraocular pressure) which causes progressive damage to the optic nerve. The optic nerve is responsible for carrying visual impulses to the brain and its damage results in loss of vision. The pressure build-up occurs because of an imbalance between the production and drainage of fluid within the eyeball. In most cases, the condition progresses slowly and insidiously, and the patient is not often aware of the condition until a late stage. By the time the patient notices a deterioration of vision, there is often already moderate to severe damage of the optic nerve. This is why this disease has been called the “silent thief of sight”.
Most glaucomas present as a slowly progressive disease, with the common forms being Primary Open-Angle Glaucoma and Chronic Angle-Closure Glaucoma. These usually affect the middle-aged or elderly people. Glaucoma may be inherited, which means that relatives of people with glaucoma have a higher risk.
Primary Open-Angle Glaucoma
This is the commonest type of glaucoma in most countries. The glaucoma progresses slowly and in the initial stage has no obvious symptoms.
Chronic Angle-Closure Glaucoma
Angle-closure glaucoma occurs commonly among Asians. Singapore has the highest reported incidence of angle-closure glaucoma in the world. In the chronic form, similar to Primary Open-Angle Glaucoma, this type of glaucoma progresses gradually, and often goes unnoticed for a long time. It results from progressive blockage of the drainage channels of the eyeball, resulting in a prolonged rise in eye pressure.
Acute Angle Closure Glaucoma
This type of glaucoma usually affects women in the middle or elderly ages. It develops because of a blockage of the fluid drainage pathway located in the angle of the eye, resulting in a rapid rise in the fluid pressure within the eye. The symptoms are sudden and dramatic requiring patients to seek medical attention urgently.
Glaucoma may arise when there is inflammation of the eyeball or when a cataract becomes too advanced and swollen. Other causes are eye surgery and injury to the eye.