The cause of Glaucoma is the increase in the pressure within the eye.
The central part of the eye is filled with a transparent and viscous liquid known as Aqueous Humor. This fluid continuously circulates within the eye. It is a major source of nourishment to eye structures that do not have capillaries for blood supply. The fluid normally flows out through its own circulation channel. The exit point of the fluid is the junction or cornea and iris.
For unknown reasons, this circulation channel gets blocked partially. This blockage increases the pressure within the eye because of fluid buildup. The increased pressure directly affects the optic nerve and causes it to degenerate overtime.
Another important factor that affects the pressure inside the eye is the overall blood pressure within the body. An increase in blood pressure increases the pressure of the fluid within the eye. Thus, hypertension is often considered an important contributing factor of Glaucoma.
An important thing to remember at this point is that increased pressure within the eye is not dangerous by itself. In fact people often have different pressure within the eye. Glaucoma is the result of the damage that the heightened pressure within the eye causes to optic nerve.
In addition, Glaucoma could develop even when the pressure within the eye is within tolerable limits. This is a special for of the disorder known as normal-tension Glaucoma.
Glaucoma could affect one eye or both eyes at the same time. Since there are no initial symptoms, it is difficult to diagnose the condition in early stages.