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Glaucoma involves increased pressure within the eye. In the normal eye, a clear fluid called aqueous humor is produced in the rear chamber and flows through the pupil into the front chamber. Once in the front part of the eye, the fluid drains out of the eye through an area called the canals of Schlemm. Aqueous humor provides structural support, oxygen, and nutrition to tissues within the eye.

• Increased IOP results from either increased production or decreased drainage of aqueous humor. The resulting increase in pressure within the eye may eventually damage the optic nerve. This increase in IOP is by far the most common risk factor for vision loss due to glaucoma, but it is not the only factor involved.

• For many years, it was believed that high IOP was the primary cause of optic nerve damage in glaucoma. Now we know that even people with normal IOP can experience vision loss from glaucoma. On the other hand, some people with high IOP never develop the optic nerve damage of glaucoma. Therefore, other factors may affect the optic nerve even when IOP is within the normal range.

• Elevated IOP is still considered a major risk factor for glaucoma, though, because studies have shown that the higher the IOP is, the more likely the optic nerve will be damaged.

• No one knows why certain ethnic groups, such as African Americans, have higher rates of glaucoma that lead to blindness. Primary open-angle glaucoma is the leading cause of blindness among African Americans and Alaska Natives, occurring 6-8 times more often than in whites, often in the earlier stages of life.

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