Prism correction

Eye care professionals use prism correction as a component of some eyeglass prescriptions.

Sometimes an image that one eye sees is not in line with what the one other eye sees, and so creates an impression of two images instead of only one. A lens which includes some amount of prism correction, will displace the viewed image, as seen by that eye, toward a direction so as to bring that image into proper binocular sync with the image that is viewed by the other eye. This prism correction is used to treat muscular imbalance or other conditions (see vergence dysfunction) that cause errors in eye orientation, such as double-vision.