glossary

A test to determine the refractive state of the eye, and the best corrective lenses required to aid in clear vision. A series of lenses in graded powers are offered to determine which provide sharpest, clearest vision.

The amount of myopia, hyperopia or astigmatism. An error in refraction of the eye. An optical defect in an unaccommodating eye in which parallel light rays do not focus sharply on the retina.

Characterizes the way a transparent optical material bends or refracts light.