Glaucoma is a group of eye disorders leading to progressive damage to the optic nerve, and is characterized by loss of nerve tissue resulting in loss of vision. The exact cause  of glaucoma is unknown. Although the disease is usually associated with an increase in the fluid pressure inside the eye, other theories include lack of adequate blood supply to the nerve.

Risk factors

Certain factors can increase the risk for developing glaucoma. They include:

• Age: People over age 60 are at increased risk for the disease. For African Americans, however, the increase in risk begins after age 40. The risk of developing glaucoma increases slightly with each year of age.
• Race: African Americans are significantly more likely to get glaucoma than are Caucasians, and they are much more likely to suffer permanent vision loss as a result. People of Asian descent are at higher risk of angle-closure glaucoma and those of Japanese descent are more prone to low-tension glaucoma.
• Family history of glaucoma: Having a family history of glaucoma increases the risk of developing glaucoma.
• Medical conditions: Some studies indicate that diabetes may increases the risk of developing glaucoma, as do high blood pressure and heart disease.
• Physical injuries to the eye: Severe trauma, such as being hit in the eye, can result in immediate increased eye pressure and future increases in pressure due to internal damage. Injury can also dislocate the lens, closing the drainage angle, and increasing pressure.
• Other eye-related risk factors: Eye anatomy, namely corneal thickness and optic nerve appearance indicate risk for development of glaucoma. Conditions such as retinal detachment, eye tumors, and eye inflammations may also induce glaucoma. Some studies suggest that high amounts of nearsightedness may also be a risk factor for the development of glaucoma.
• Corticosteroid use: Using corticosteroids for prolonged periods of time appears to put some people at risk of getting secondary glaucoma.

Categories of Glaucoma

Primary open-angle glaucoma: This is the most common form of glaucoma. Glaucoma is thought to develop when the eye's drainage system becomes inefficient over time. This leads to an increased amount of fluid and a gradual buildup of pressure within the eye.

 Angle-closure glaucoma: This type of glaucoma, also called closed-angle glaucoma or narrow angle glaucoma, is a less common form of the disease. It is a medical emergency that can cause vision loss within a day of its onset. It occurs when the drainage angle in the eye (formed by the cornea and the iris) closes or becomes blocked. Angle-closure glaucoma can be chronic (progressing gradually) or acute (appearing suddenly).

Secondary glaucoma: This type of glaucoma occurs as a result of an injury or other eye disease. It may be caused by a variety of medical conditions, medications, physical injuries, and eye abnormalities. Infrequently, eye surgery can be associated with secondary glaucoma.

Normal-tension glaucoma: In this form of glaucoma, eye pressure remains within what is considered to be the "normal" range, but the optic nerve is damaged nevertheless.

Ocular hypertension:  An increase in the pressure in your eyes that is above the range considered "normal" with no detectable changes in vision or damage to the structure of your eyes. The term is used to distinguish people with elevated pressure from those with glaucoma.

Lifelong treatment

There is no cure for glaucoma. Patients with glaucoma need to continue treatment for the rest of their lives. Because the disease can progress or change silently, compliance with eye medications and eye examinations are essential, as treatment may need to be adjusted periodically.By keeping eye pressure under control, continued damage to the optic nerve and continued loss of your visual field may slow or stop. Early detection, prompt treatment and regular monitoring can help to control glaucoma and therefore reduce the chances of progression of vision loss.