glossary

The optical power (of a lens) required for near vision, in addition to that required for far vision.

A condition that includes deterioration of the macula and resulting in loss of sharp central vision. Most common cause of decreased vision after age 60.

This term describes a visual field defect in which either the upper or lower half of the visual field is selectively affected. The selective abnormality often creates a horizontal line across the visual field (known as “respecting the horizontal meridian”). Altitudinal defects occur in retinal vascular disease, glaucoma, and other disorders that affect the eye itself.