The Facts
The cornea is a special layer on the surface of the eye that does most of the work of bending light as it enters the eye. Light must be bent properly so that it creates a sharp image. Theoretically, the eye's cornea should be perfectly round, like a slice off the surface of a ping-pong ball. Astigmatism is a condition in which the cornea is oval, like the bottom of a dessert spoon. This means that the focus is smeared so that while lines in one direction may be sharp, lines in another direction will be blurry.
Causes
We don't know what causes astigmatism, but we know it tends to run in families. Some people are born with astigmatism. Others get astigmatism later in life, sometimes after eye damage. Everyone has a tiny degree of astigmatism - no cornea is perfectly round. It's only a problem when it interferes with vision.
