Glaucoma - Diagnosis

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Perimetry and Other Tests of the Visual Fields

If there is indication of optic nerve damage, the eye professional will conduct tests of the visual fields (the areas that the patient can see). In most people with glaucoma, the first areas to become noticeably impaired are the peripheral visual fields (areas of sight that are not directly in front of a person but more to the sides).

Click the icon to see an image of the visual field test.

Standard Perimetry Tests. Perimetry tests are used to check peripheral vision. One variation of this test is as follows:

• A person sits closely facing a large computer-like monitor.
• Small bright white lights flicker on and off hundreds of times, at different places on the screen, while the patient clicks a button whenever one of the lights is seen.
• The machine prints out a report that maps any blanked-out areas in the person’s vision.

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The test is complex and lengthy; elderly people and those with short attention spans may be inappropriate candidates. Other perimetry tests, some requiring less time to administer and some using "virtual reality" techniques, are currently being developed.

Other Tests. Other visual field tests are being developed that can detect abnormalities years before they can be detected by standard perimetry. Experts recommend some of these tests in selected patients with suspected glaucoma.

For example, a screening test called frequency doubling technology (FDT) checks for changes in particular cells in the retina that are indications of early glaucoma. It takes less than a minute to perform.

Another test called short wave automated perimetry (SWAP) uses colors (blue-on-yellow) and also detects very early abnormalities in the visual field. Testing time is longer than with FDT, however, and the presence of certain types of cataracts can interfere with its accuracy.

Markers

ELAM-1. Endothelial leukocyte cell adhesion molecule 1 (ELAM-1) is a molecule that has been found in glaucoma but not in healthy eyes. This molecule may prove to be a "marker" and its presence may be helpful in diagnosing glaucoma.

Test for Acute Closed-Angle Glaucoma

A simple test using a penlight helps determine the risk for acute closed-angle glaucoma. A beam of light is directed from the side of the face toward the patient's iris. If no shadow appears on the nose, then most likely the angle is wide enough to dilate. Using an instrument called a gonioscope, ophthalmologists can also inspect the front of the eyes and assess the drainage angle between the cornea and the iris and the channels in the trabecular meshwork. This test can differentiate between closed- and open-angle glaucoma.

Review Date: 03/03/2007
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).