Ocular Surface


Lt Col Reynolds
The ocular surface, or surface of the eye, consists of the cornea and the conjunctiva, and is bordered by the upper and lower eyelids. Dr. Flemings, what can you tell us about the ocular surface?

Lt Col Flemings
Well, Dr. Reynolds, unlike the rest of the body, which is covered by skin, the ocular surface is covered by a thin layer of tear film, which is formed by the tears that spread across the eye’s surface every time a person blinks. Having a stable tear film when the eye is open protects the eye against infection and contributes to eye comfort and clear vision.

Tear film has three layers. The outer layer, called the lipid layer, is oily and keeps tears from evaporating too quickly. The middle layer is called the aqueous layer, which nourishes the cornea and conjunctiva. The bottom, or mucin, layer helps spread the aqueous layer across the eye to ensure that the eye remains wet.

Excess tears drain through ducts in the inner corner of the eyelids. When the production and drainage of tears is out of balance, the tear film may become unstable or inadequate, causing "dry eyes."

The cornea is transparent, or clear, and is the part of the eye that covers the colored iris. It plays a crucial role in the refraction process that allows a person to see.

The conjunctiva is a thin membrane covering the inner surface of the eyelid and the white part of the eyeball, called the sclera.