Visual field testing, also known as perimetry, measures your complete field of vision — both what you see straight ahead and what you can detect off to the sides, without moving your eyes. It's one of the primary tools we use to evaluate peripheral vision and to detect blind spots that you might not notice in everyday life.
How the Test Works
During visual field testing, you'll look into a bowl-shaped instrument and focus on a central target. As small points of light appear at different locations within your field of vision, you press a button each time you notice one, while a computer tracks which points you detect and which you miss. One eye is tested at a time, with the other eye patched, and the resulting printout maps your field of vision, highlighting any areas of reduced sensitivity.
Why It's Used
Visual field testing is most commonly associated with monitoring glaucoma, since peripheral vision loss is often an early and otherwise unnoticeable sign of the disease. It's also used to evaluate vision loss related to the optic nerve, retina, or neurological conditions affecting the visual pathway, such as after a stroke. Because the test produces objective, repeatable measurements, it's valuable for tracking whether a condition is stable or progressing over time.
What to Expect
The test itself is painless and non-invasive, though it does require sustained attention and typically takes several minutes per eye. There's no need for dilation, and you can resume normal activities immediately afterward. Your provider will review the results with you and explain how they fit into your overall eye health picture.