glossary

An inheritance pattern in which a person must inherit two copies of an abnormal gene (one from each parent) in order to develop the disease. If two individuals each carry one copy of an abnormal gene, then each child born to these two parents will have a 25% chance of receiving 2 copies of the abnormal gene and as a result, inherit the disease. Cystic fibrosis is an example of an autosomal recessive disease.

Lens with two points of focus, designed to relieve presbyopia. The lower part of the lens allows near vision; the rest of the lens is designed for far vision.

A lens having two separate and distinct points of focus (focal lengths) which incorporate two different powers in each lens, usually for near and distance corrections.