Because it has no noticeable symptoms, glaucoma is a complex disease to detect without regular, complete eye exams.
During a glaucoma evaluation, your ophthalmologist (Eye M.D.) will perform the following tests:
Tonometry
Your ophthalmologist measures the pressure in your eyes (intraocular pressure, or IOP) using a technique called tonometry. Tonometry measures your IOP by determining how your cornea responds when an instrument (or sometimes a puff of air) presses on the surface of your eye. Eyedrops are usually used to numb the surface of your eye for this test.
Gonioscopy
For this test, your ophthalmologist inspects your eye’s drainage angle—the area where fluid drains out of your eye. During gonioscopy, you sit in a chair facing the microscope used to examine the inside of your eye. You will place your chin on a chin rest and your forehead against a support bar while looking straight ahead. The goniolens is placed lightly on the front of your eye, and a narrow beam of light is directed into your eye while your doctor looks through the slit lamp at the drainage angle. Drops will be used to numb the eye before the test.
Ophthalmoscopy
With this test, your ophthalmologist can evaluate whether or not there is any optic nerve damage by looking at the back of the eye (called the fundus). There are two types of ophthalmoscopy: direct and indirect. With direct ophthalmoscopy, your ophthalmologist uses a small flashlight-like instrument with several lenses that magnifies up to about 15 times. This type of ophthalmoscopy is typically performed during a routine physical examination. With indirect ophthalmoscopy, the ophthalmologist wears a headband with a light attached and uses a small, handheld lens to examine the inside of your eye. Indirect ophthalmoscopy provides a clearer view of the fundus, even if cataracts obscure your natural lens.
Visual field test
The peripheral (side) vision of each eye is tested using visual field testing, also known as perimetry. For this test, you sit at a bowl-shaped instrument called a perimeter. While you stare at the center of the bowl, lights flash. Each time you see a flash, you press a button. A computer records your response to each flash. This test checks for any areas of vision loss. Loss of peripheral vision is often an early sign of glaucoma. In certain types of glaucoma, decreased sensitivity can be found near the centre of the vision.
Photography
Sometimes, photographs or other computerized images are taken of the optic nerve to inspect it more closely for damage caused by elevated intraocular pressure.
Special imaging
Different scanners may be used to better determine the 3D structure of the optic nerve head or retinal nerve fibre layer. With the newer, higher-resolution OCT scans offered by Spectral Domain and Swept Source devices, changes can be detected in the ganglion cell layer of the retina. The axons of these cells join downstream to form the optic nerve.
Each of these evaluation tools is a meaningful way to monitor your vision, helping to ensure that glaucoma does not rob you of your sight. Some of these tests will not be necessary for everyone. Your ophthalmologist will discuss which tests are best for you. Some tests may need to be repeated regularly to monitor any changes in your vision that may be caused by glaucoma.
© 2025, 2021, 2009 Robert M Schertzer, MD, MEd, FRCSC, based on 2007 The American Academy of Ophthalmology
