Refractive Errors

The Normal Eye

The eye's surface is convex, and light rays that hit it bend toward its center.

In an eye that has a normally-curved corna and the correct shape, an image focuses exactly on the retina.

Nearsightedness (Myopia)

When the eyeball is too long or the corna is too steeply curved, light rays

focus in front of the retina. Near objects are clearly seen while distant

objects are not.

Farsightedness (Hyperopia)

When the eyeball is too short or the corna is too flat, light rays focus behind the retina. Distant objects are seen clearly while near objects are not.

Astigmatism

When the surface of the cornea is unevenly curved, light focuses at multiple points on the retina, leading to blurred or multiple vision.