Overview

The human body has evolved in a rough and ready response to environmental demands. The eye is no exception to this rule, for very few people have perfect vision. The many with imperfect vision fall into two general groups, the farsighted who have trouble focusing on near objects (presbyopes) and the nearsighted who have poor vision beyond a very short distance (myopes). Presbyopes require spectacles with convex lenses that curve outwards on both surfaces, myopes need lenses that are concave, or curve inwards. Attempts to correct human vision are as old as human society. The oldest known lens, of polished rock crystal, was found in the ruins of ancient Nineveh. The classical Roman writer Seneca is said to have read all the books in Rome by using a glass globe of water to enlarge the handwritten letters. However, spectacles in some...