Illinois Society for the Prevention of Blindness

The most reliable way to detect open-angle glaucoma is through a comprehensive eye examination with dilated pupils--which, when indicated, includes a visual field test.

To dilate, or enlarge, the pupils, the eye care professional places medicated drops into the eye. By so doing, the practitioner can better examine the back of the eye for early signs of disease, such as optic nerve damage, before noticeable vision loss occurs.

Tonometry is a common and painless test to measure intraocular pressure. In this test, an eye care professional uses an instrument called a tonometer to measure the fluid pressure in the anterior chamber. However, because elevated fluid pressure is only one characteristic of open-angle glaucoma, tonometry does not always indicate whether or not a person has the disease. In fact, many people with elevated fluid pressure never develop any form of glaucoma, while people with seemingly normal pressure during an examination will develop the disease. For this reason, tonometry should be viewed as one important component of the overall examination for glaucoma, but should not be the only test used to detect glaucoma.

When indicated, a visual field test, also called perimetry, is used by the eye care professional to measure the patient's field of vision. This test is particularly important because it can detect a patient's early loss of peripheral vision, a sign of open-angle glaucoma.

The National Eye Health Education Program recommends that people at higher risk undergo an eye examination through dilated pupils at least once every two years.