How to get your peripheral vision tested

A visual field test can check how well your peripheral vision works and catch conditions ranging from glaucoma to strokes.
Most eye exams include a visual field test, which basically checks your peripheral or side vision. When your eyes are fixed on a single point, it measures what you can see, and how well, above and below, as well as to the sides of your field of vision.

Blind spots or abnormalities can indicate a variety of eye and brain disorders. For example, optic nerve damage caused by glaucoma is a specific, readily identified visual field defect. Other eye problems caught by the test can include optic nerve damage from disease or damage to the light-sensitive retina.

Strokes, brain tumours and other neurological issues can also be detected by visual field tests.

There are a variety of ways to conduct the test.

With this basic test, the eye doctor asks the patient to cover one eye and stare at a fixed object, like the examiner’s eye. Then the doctor moves his or her hand out of the patient’s visual field and then brings it back in. The patient signals when it comes back into view.

Only testing the outside of the visual field, this exam is not as comprehensive as some of the other visual field tests. But it can help the doctor decide if further testing is required.

Perimetry is a comprehensive test that measures light sensitivity in the visual field by detecting test targets on a defined background. As the name suggests, it is a method of testing the perimeter of the visual field.

The automated perimetry test uses a computer program. The patient peers into a dome-shaped instrument and the doctor instructs them to look at an object in the middle of the dome throughout the test.

As the patients spot flashes of light on the dome, they press a button, allowing the computer program to create a map of their visual field.

• Tangent screen: Using a white tangent screen, this simplest form of perimetry tests vision by presenting different sized pins attached to a black wand, which may be moved against a black background.
• Goldman perimeter: Here a hollow white spherical bowl is positioned a set distance in front of the patient. The doctor presents a test light of variable size and intensity, which either moves or stays in place. Once quite popular, the Goldman method has been overtaken by automated perimetry.

This test measures electrical activity generated by the photoreceptor cells in the retina when the eye is stimulated by a special strobe light or a reversing checkerboard pattern of light. An electrode on the cornea captures the measurement and creates a graphic record called an electroretinogram, or ERG.

The test is useful in capturing conditions such as a detached retina or changes to the retina caused by diabetes or arteriosclerosis.

If glaucoma is detected, the visual field test can be used to determine the severity of disease and what kind of follow-up care is required. After the initial diagnosis, the doctor will repeat the visual field test to check for any worsening of glaucoma, in three or 12 months, depending on how bad things are.