There are several ways to test your peripheral (side) vision, but they all involve covering one eye and staring straight ahead with the other. In the most basic test, your doctor moves her hand through your field of vision, and asks if you can see how many fingers she is holding up. You may also be asked to watch a screen as dots of lights flash. Usually, you’ll press a button each time you see a dot, enabling a computer to map your field of vision. The test detects blind spots due to glaucoma, a stroke or other ailments.