Health Conditions

What causes it?

The rise in intraocular pressure (IOP) that causes glaucoma results when the eye is unable to correctly drain the aqueous humor, the fluid circulating inside the eyes. The inability of the eye to drain this fluid may be due to blockage or closure of the draining pores from swelling of the surrounding tissue, problems with the muscles that open the area around these pores, or trauma or scarring from other eye diseases. There is also a hereditary component to developing this eye disease. Some medications have been linked to either causing or worsening glaucoma, but these are not thought to be the main cause of the disease. Usually, the cause of glaucoma is unknown, although some types are due to trauma or other diseases.

To understand how this increased pressure affects the eye, think of your eye as a balloon. When there is too much air blown into a balloon, pressure builds, and the balloon wall thins. Similarly, the eye's walls become weaker and weaker as the pressure increases, especially where the optic nerve is located. The optic nerve carries visual information to the brain through more than 1 million nerve fibers. As the pressure builds, the optic nerve is damaged, causing vision loss. Both types of glaucoma can lead to blindness by damaging the optic nerve. It is interesting to note that even people with normal IOP can suffer damage to the optic nerve--in fact, 25 to 30 percent of people with glaucoma do not have elevated IOP levels.