Exams and Tests

Many different methods are used to measure pressure within the eye. Other tests determine whether you have glaucoma and how advanced your glaucoma may be. Most diagnostic tests need to be repeated on a regular basis to follow the presence or progression of glaucoma.

• Air puff test: The "air puff" test is the most common. This test is a way to measure the IOP without having to actually touch the eye. For this test, you sit in front of a machine with your chin resting on a brace. The eye doctor points a small jet directly at your eye. This jet then delivers a quick puff of air onto the surface of your eye. By measuring the response of the eye to the puff of air, the doctor can make a rough estimate of the intraocular pressure. This is a good screening test for elevated IOP, but it is not very accurate.

• Direct tonometry: Direct tonometry on the surface of the front part of the eye is a much more accurate measurement of IOP. It, however, requires greater skill and expertise to perform. A sensor is placed gently on the surface of an anesthetized eye, and a very accurate IOP is measured.

• Dilation: An examination to inspect the back of the eye through dilated (widened) pupils is required to diagnose glaucoma. To do this, drops are put into the eyes to enlarge, or dilate, the pupils. This allows the eye doctor to see more of the inside of the eye. An eye doctor can recognize a characteristic divot or depression in the optic nerve at the back of the eye caused by damage from the elevated eye pressure. This enlargement is called "cupping" of the optic nerve and means the condition may be relatively advanced.

• Perimetry: Another test, perimetry, is used to determine the presence of defects within the visual fields, particularly vision to the side (called your peripheral vision). Because people with glaucoma tend to lose their vision from the outer edges to the center, checking peripheral vision is very important. In perimetry, a machine is used to test your peripheral vision. You are asked to look at a series of blinking lights. By recording when you see the lights, an accurate map of your peripheral vision can be made. If you have glaucoma, you will have decreased peripheral vision. This test can be performed to follow the progress of your glaucoma or to determine the severity of the initial diagnosis.