This graphic shows a side view of four eyes illustrating the following four visual conditions:
The cornea and the lens are responsible for focusing light on the retina. With normal vision, light striking the cornea is focused directly on the central region of the retina.
Myopia, or nearsightedness, occurs when either the cornea is too steep and/or the eye is too long, and light is focused in front of the retina. Close objects appear clear and far objects are blurry.
Hyperopia, or farsightedness, occurs when either the cornea is too flat and/or the eye is too short, and light is focused behind the retina. Distant objects appear clear and close objects appear blurry.
Astigmatism occurs when the surface of the cornea is oval-shaped, rather than round. Light rays have more than one focal point and can focus on different areas of the retina. Astigmatism creates double, distorted or blurry vision.
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2002-JAN-30.