The white part of the eye is known as the sclera.

Light enters the eye through the cornea, which is made of transparent tissue. The cornea is one of the elements that provides focusing power for the eye.

The pupil is the dark, round opening in the center of the colored iris. It acts as an aperture to regulate the amount of light entering the eye by becoming smaller in bright light and larger in dim light.

Directly behind the pupil is the lens, which also provides some of the eye's focusing power.

During the reading process, muscles in the ciliary body contract, which changes the shape of the lens to bring near objects into focus. Around age 40, the lens becomes rigid and the muscles are no longer able to change its shape, so reading glasses or bifocal lenses become necessary.

The retina is made of photosensitive cells that capture light images and translate them into electrical impulses that travel to the brain via the optic nerve. The macula is a specialized area in the center of the retina that is responsible for fine detail.

There is a clear gel-like substance called vitreous inside the eye's cavity which helps maintain the spherical shape of the eye (not shown).

The contour of your cornea, the power of your lens, and the length of your eye determine how clearly you can see. If these elements are matched together perfectly, light rays are properly focused and you can see clearly.

If these elements are not properly coordinated, then your vision will be blurry. These focusing (we call them “refractive”) problems are referred to as myopia, hyperopia, astigmatism, and presbyopia.

Back   |   Next