Glaucoma is a group of eye diseases with characteristic damage to the optic nerve resulting in permanent loss of vision. The fluid pressure within the eye ( intra-ocular pressure) is elevated in most, but not all, of these diseases. Fluid pressure rises as a result of imbalance between the production and drainage of the fluid. When the fluid pressure exceeds the level that the optic nerve can tolerate, the optic nerve suffers damage. The eye pressure at which damage occurs varies between different individuals.
Damage to the optic nerve usually causes loss of vision in the periphery so that it is not noticeable in early stages. Central vision remains normal till late in the disease. Patients often do not experience any pain, redness, tearing or blurring of vision till the disease is very advanced and most of the vision is irreversibly lost. Therefore, Glaucoma is often called the “Silent Thief of Sight”.