THE NORMAL EYE
One of the most critical components of your eye is the cornea – the "window" of your eye. The job of the cornea is to bend, or refract, light rays precisely on the retina.

THE NEAR-SIGHTED EYE
Myopia (near-sightedness) is the result of an eyeball which is too long, or a cornea which is too curved. In both cases, light rays entering your eye fall short of the retina, and objects in the distance appear blurred. If you have this condition, you are not alone; more than 70 million people in North America have myopia.

THE FAR-SIGHTED EYE
Hyperopia (far-sightedness), is the opposite of myopia. Here, your eye is too short or your cornea is less curved. Consequently, light rays entering your eye fall behind the retina. This results in blurred vision – which is worse at near distances than far.

THE ASTIGMATIC EYE
Astigmatism occurs when your cornea is shaped like a football with two different curvatures. Images appear blurred or ghost-like because light rays are refracted unequally. In extreme cases, images both near and far appear blurred. Many people who have myopia also have astigmatism.