Know your Eye

Know your Eye

The main parts of the human eye are the cornea, iris, pupil, aqueous humor, lens, vitreous humor, retina, and optic nerve. To understand how the eye sees, it helps to know the eye structures and functions:

Cornea:

Light enters through the cornea, the transparent outer covering of the eye. The eyeball is rounded, so the cornea acts as a lens. It bends or refracts light.

Aqueous Humor:

The fluid beneath the cornea has a composition similar to that of blood plasma. The aqueous humor helps to shape the cornea and provides nourishment to the eye.

Iris and Pupil:

Light passes through the cornea and aqueous humor through an opening called the pupil. The size of the pupil is determined by the iris, the contractile ring that is associated with eye color. As the pupil dilates (gets bigger), more light enters the eye.

Lens:

While most of the focusing of light is done by the cornea, the lens allows the eye to focus on either near or distant objects. Ciliary muscles surround the lens, relaxing to flatten it to image distant objects and contracting to thicken the lens to image close-up objects.

Vitreous Humor:

A certain distance is required to focus light. The vitreous humor is a transparent watery gel that supports the eye and allows for this distance.