By age 16, about 20 percent of all children develop vision problems, which are correctable with glasses. Special reflex tests are used to test infants under one year of age.
Some authorities recommend testing at an earlier age.
In all instances, if a decrease in visual ability, crossed eyes or other eye problems are noticed, the eyes should be tested. Several tests will reveal any sight-related problems, in addition to considering the patient's eye and health history and conducting a standard eye examination . The red reflex test is performed in a darkened room with a light source at an arm's length from the child. For the fixation test , a light or a small object is moved in front of the child's eyes, both of which should follow the object in coordinated movements. Stereopsis testing , a trial of binocular depth perception, requires polarized glasses and special target cards composed of random-looking dots.