Information about Glaucoma
A common treatable cause of blindness in the United States, glaucoma is a condition in which deterioration of the optic nerve leads to progressive loss of field of vision. Worldwide, glaucoma is among the top three causes of blindness. In the United States, about 1.6 million Americans age 40 years and older have glaucoma. Because the most common form of the conditionopen angle glaucomadoes not cause symptoms in its early stages, about half the people with glaucoma do not realize they have it.
The risk of glaucoma varies with race and age. The condition is more common in blacks and Hispanics than in whites, and it occurs more frequently with increasing age. According to data from the National Eye Institute, the prevalence of glaucoma is less than 1% in people age 40 to 49. By age 70, it is nearly 4%; by age 80, nearly 8%. People with diabetes also are at increased risk.
Two main forms of glaucoma exist:
- Open-angle glaucoma progresses slowly and produces no obvious symptoms until its late stages. It is equally common in men and women and is responsible for about 90% of glaucoma cases.
- Closed-angle glaucoma, which is responsible for most of the remaining 10% of glaucoma cases, occurs more often in people of Chinese descent and some other Asian groups. Women are at greater risk than men.
Both types of glaucoma can lead to blindness, which is caused by damage to the optic nerve. Many people with glaucoma have intraocular pressure (IOP) that is too high for the optic nerve to tolerate. Susceptibility to IOP varies from person to person, and risk factors other than IOP play a role in the development of glaucoma. However, early detection and treatment of elevated IOP levels can help prevent damage to the optic nerve.
Interestingly, people with normal IOP also can suffer damage to the optic nerve. This condition is referred to as normal- or low-pressure glaucoma or low-tension glaucoma. Although the majority of people with glaucoma in North America have elevated IOP levels, many have normal-pressure glaucoma.
Some researchers believe these individuals have extremely pressure-sensitive optic nerves. Others hypothesize that different factors, such as compromised blood circulation, may damage the optic nerve.