The ocular surface is the surface of the human eye. This includes the cornea, the conjunctiva, and the tear ducts which connect to them. The definition also sometimes includes the eyelids.
The cornea is the most easily recognizable part of the ocular surface. It is made up of a clear piece of tissue which covers the iris. From the side, it looks like a dome. The cornea protects the sensitive iris while still allowing light to reach the pupil, which leads to the lens and the light-sensing cones of the inner eye.
Nerve endings also make up the cornea. These help to sense when there's something in the eye and signal the tear ducts to produce more fluid to get it out. The sensitivity of the cornea also means that some people cannot easily wear contacts.
The cojuntiva is the clear mucous membrane that covers the parts of the eyeball that are not covered by the cornea. Like the cornea, it is also clear. The cojuntiva is thought to have three parts: the part which covers the eye itself, the part which lines the inside of the eyelids, and the part where these two surfaces meet when the eye is shut.
This area produces mucus and some tear fluid. This keeps the ocular surface moist and lubricated so that the eyes can blink easily. It is nourished by many blood vessels. If it becomes infected, these blood vessels can become red and inflamed-looking. This disease is known as "pinkeye."
Finally, tear ducts are also considered part of the ocular surface. There is one in each corner of the eye. They produce tears which cover and lubricate the ocular surface. If these ducts become clogged or otherwise unable to produce tears, the resulting lack of tears and dryness can be extremely painful.
The eyelids have a twofold purpose. They protect the rest of the eye from dust and debris. Also, the action of blinking spreads tears over the eye to keep it moist.
In the early 2000s, a review journal called Ocular Surface was formed in order to encourage the research and development of treatments for disorders that affect the ocular surface. It seeks to provide a place where hundreds of new studies can easily be accessed.