The eye is a miraculous creation. This illustration points out many of its key parts.
You’ve heard it said many times, and it’s true: your eye does work very much like a camera, and it has similar parts.

Light coming from objects passes through the cornea, a clear protective shield in the front of your eye. Then it goes through the pupil, an adjustable opening (often called aperture) in the center of the iris, or colored part of your eye.

Behind the pupil is the lens. Muscles inside your eye control the shape of the lens, focusing it (as a camera lens does) to view objects at different distances.

The light rays pass through the dark chamber of your eyeball to the retina (in the camera, this is the film) at the back of your eye. The retina contains nerve cells that signal to your brain through the optic nerve. As your brain receives the messages, you see the object before you.

If light rays do not focus properly on your retina, you have a refractive error. Common refractive errors include myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia.

If you are nearsighted, light rays coming into your eye focus in front of the retina, causing blurry vision. Often, this results when the cornea is too steeply curved.

If you are farsighted, light rays focus behind the retina, which also results in blurry vision. This results most often when the cornea is too flat. In astigmatism, the cornea has an irregular curvature that produces two different focal points. Presbyopia is simply the inability of the eye to read close up, due to aging of the natural lens of the eye.