glossary

Lens for near vision only shaped like the lower half of a normal lens.

Far-sightedness, an eye that is too short and/or insufficiently powered. The image forms behind the retina, which explains why the hyperopic subject has better eyesight in far vision than in near vision. In cases of mild hyperopia, the subject sees correctly in far vision by compensating the hyperopia through accommodation. In cases of severe hyperopia, the eye can no longer compensate in this way. Focusing defect in which an eye is underpowered. Light rays coming from a distant object strike the retina before coming to sharp focus, causing blurred vision. Corrected with plus (convex) lenses.

Long-sightedness, requiring a convex lens to focus the vision.