How the Eye Works

Sharp vision depends on many factors. The parts of the eye work together to refract, or bend, and focus light rays. For normal vision, light must focus onto the retina. 

Cornea

Light enters the eye through this clear, dome-shaped tissue. The cornea also bends light rays to help focus them. Problems with the cornea's shape can affect vision.

Pupil

This circular window in the center of the iris opens and closes to let the right amount of light into the eye.

Iris

This is the colored part of the eye. It contains muscles that dilate or open, and constrict or close, the pupil.

Lens

This disk of clear tissue behind the pupil changes shape to help focus light.

Retina

This thin layer of light-sensitive tissue lines the inside of the eye. The retina sends signals to the optic nerve.

Optic nerve

This nerve carries signals from the retina to the brain. The brain then interprets these signals to make images. These images are what you see.