Vision Terminology

Nearsightedness
Also known as myopia, the light entering the eye doesn't focus on the retina, but at some point in front of it. It is frequently caused by an abnormally long eye shape, or by an excessive curvature of the cornea. When this occurs, objects at a distance appear blurry.

Farsightedness
Also known as hyperopia, the light entering the eye focuses at a point behind the retina, making objects closer to the eyes blurry, while those far away are in focus. It is frequently caused by an abnormally short shaped eye, or an excessively flat cornea.

Astigmatism
This is caused not by the length of the eye, but the shape. The normal cornea is shaped like a ball. An astigmatic eye, however, takes a football-like shape. The result is that objects are not focused into a single image. Vision is blurred and distorted. Most commonly, people with nearsightedness also suffer from astigmatism.

Presbyopia
The inability to focus on objects close-up. The condition occurs when the lens of the eye loses its ability to focus at close range. It is a normal occurrence, usually beginning in the early forties, tending to decrease visual acuity with age.