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How the Eye Works

By understanding the eye and by working closely with your medical team to prevent, slow or stop eye damage, you play an important part in preserving vision.

The eye functions like a camera, with a lens in front and the retina, a light-sensitive tissue analogous to film in a camera, in back. The retina is a delicate membrane of nerve tissue lining the back of the eye that transforms light energy entering the eye into a neural signal that allows sight.  The area behind the lens and in front of the retina is filled with a thick fluid called the vitreous humor.

Sight occurs when light bounces off an object and then passes through the eye’s cornea and lens, which focus the image on the retina. The retina changes the light signal into nerve impulses, which exit at the back of the eye along the optic nerve. The optic nerve then sends the message to the brain, which interprets the image. Wherever there is damage to the retina, the eye is unable to send these messages to the brain.

When a physician looks into your eyes, he or she sees a pale flat object that looks like a tiny pancake on the back of the eyeball. This structure, called the optic disc or optic nerve head, is the flat side of the optic nerve facing the doctor. Radiating from the optic disc, like spokes of a wheel, are blood vessels. These vessels supply the eye with nourishment. It is these vessels that can be damaged by diabetes.

Page last updated: September 20, 2019