Diagnosing Glaucoma - Glaucoma: Eye Care

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Diagnosing glaucoma

Most doctors agree that a regular eye exam should include glaucoma screening beginning at age 40, and people who are at higher risk should be screened annually. These include people with a family history of the disease, people of African American ancestry, and people with diabetes. Medicare began covering annual dilated eye exams as of January 2002.

During your exam, the ophthalmologist evaluates pressure in the eye through tonometry. Normal pressure is 8–21 millimeters of mercury (mm Hg), but people with eye pressure in this range may still develop the disease. Likewise, those who have slightly elevated pressure may not be destined to get glaucoma; how much stress the optic nerve can withstand differs for each person and each eye.

A thorough evaluation of the optic nerve should be part of a routine eye exam. This is best done with a dilated pupil. The doctor uses both a slit lamp and ophthalmoscope to look for any deterioration of the nerve. If the optic disc, the front surface of the optic nerve, is affected by glaucoma, the doctor may observe a characteristic called cupping: The disc may appear indented, and its color — normally pinkish yellow — may turn pale and more yellow because the advancing disease has hindered blood flow to the area.

If the doctor suspects glaucoma, he or she may perform an examination called gonioscopy. This procedure involves placing a special contact lens on the surface of an anesthetized eye. The lens has special mirrors and facets that, when studied through the slit lamp, give a detailed view of the corner of the eye and show whether the drainage angle is open, narrowed, or closed. To confirm the presence of the disease, the doctor may repeat the tonometry test, particularly because pressure in the eye may vary at different times of the day.

For patients with glaucoma, the ophthalmologist may use a technique called fundus photography to produce three-dimensional pictures of the optic disc, which serve as a baseline for later comparisons of the disc. A change in its appearance usually means that pressure has not been controlled and more treatment is needed. An ophthalmologist may also obtain specialized computer-generated images of the optic nerve to estimate the thickness of the nerve fiber layer. Finally, a visual field examination can determine whether peripheral vision is damaged.

Last updated:	June 19, 2007