Glaucoma is an eye disease where the fluid pressure within the eyeball is too high and damages the optic nerve, which carries visual impulses from the eye to the brain. This raised pressure is damaging to sight as it can injure the delicate nerve fibres contained in the retina and the optic nerve at the back of the eyeball. Known as the silent thief of sight, the vast majority of cases develop slowly, and the patient is normally unaware of the gradual loss of sight until very late in the disease when vision is seriously affected.
Glaucoma is classified according to the configuration of the angle (the part of the eye between the cornea and iris mainly responsible for drainage of aqueous humor) into open angle and angle-closure glaucoma. Primary angle closure glaucoma is the major form of glaucoma in Asia.