The exact cause of glaucoma is not known, but risk factors include family history, age, race, and certain medical conditions.
Primary open-angle glaucoma, the most common form of glaucoma, is usually associated with abnormally high pressure in the eye. This pressure is due to increased resistance to the flow of aqueous humor from the eye.
Aqueous humor is a clear fluid that fills the anterior segment of the eye and flows out through the trabecular meshwork and the Schlemm's canal. Normally, the amount of aqueous humor produced daily by the ciliary body is equal to the amount that flows out of the eye, but in glaucoma, there is a decrease in outflow of aqueous humor and an increase in its production, causing increased pressure inside the eye. This increase in pressure may cause damage to the optic nerve and can lead to permanent vision loss. Normal pressure glaucoma occurs in some individuals with POAG in whom the pressure in the eye is not abnormally high.
Primary angle-closure glaucoma occurs when the drainage angle of the eye becomes blocked by iris, causing decreased outflow of aqueous humor and increased pressure. This form of glaucoma usually affects people over age 40. Risk factors for PACG include the following eye conditions:
Pseudoexfoliation myopia hyperopia
Generally, PACG begins as an asymptomatic disease that slowly increases in severity and may even occur in both eyes in a short period of time.
Primary angle closure glaucoma is a potentially blinding eye disease in which a sudden and severe increase in intraocular pressure leads to severe damage to the optic nerve. Glaucoma damage is irreversible and progresses until the point of total vision loss. Primary angle closure glaucoma can be both acute and chronic. The more common chronic condition is generally asymptomatic. This form of glaucoma develops slowly over many years, and, if left untreated, it will eventually lead to blindness.
A sudden, painful episode is characteristic of the acute form of PACGand should be treated quickly to prevent permanent vision loss.
There are three major risk factors for PACG:
Ethnicity: People of Asian descent, particularly people from India, are at high risk for primary angle closure glaucoma. People of Hispanic origin and African-Americans are also at increased risk for primary angle closure glaucoma.
Gender: Women of Asian descent have been shown to have a much higher than average risk of developing this type of glaucoma. Specifically, a 2001 study showed that one in every nine women of Chinese descent over the age of 40 will develop primary angle closure glaucoma, comparedwith one in every 60 men.