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The conjunctiva is a thin membrane that lines the inside of your eyelids (both upper and lower) and covers the outer portion of the sclera (white part of the eye). It does not cover the cornea, which is the clear covering on the front of the eye. The area where the conjunctiva meets the cornea is called the limbus.
Tenon’s capsule is a sheath that surrounds the eyeball and merges with the conjunctiva in the limbal area. This capsule protects the eye and prevents ocular infections from spreading behind the eye.
The part lining the inner surface of the eyelids is called the palpebral or tarsal conjunctiva. The part covering the sclera is called the bulbar conjunctiva. The bulbar and palpebral conjunctiva comprise one continuous piece of tissue, connecting at the fornix.
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The conjunctiva protects the eye from foreign objects such as dust and dirt, as well as from bacteria and other microbes that can cause infections. Your conjunctiva also contains many blood vessels, which circulate oxygen and nutrients throughout the eye.
Another function is to provide lubrication to the front surface of the eye and the inner eyelids. The conjunctiva contains goblet cells, which secrete mucin. Your tear film is comprised of three layers:
You need all three layers intact to have a healthy ocular surface. Without proper moisture, you can develop dry eye symptoms. Additionally, blinking your eyelids would cause friction that causes further irritation.
If you wear contact lenses, you may wonder if you can get a lens stuck behind the eye. Because of the conjunctiva, it is physically impossible. Although the lens can get stuck underneath the eyelid, it cannot go behind the eye.
The conjunctiva is very thin and practically transparent (except for the blood vessels) so that any tissue underneath the conjunctiva is visible.
Some people confuse the conjunctiva for the white part of the eye, which is the sclera. The sclera is a tough, opaque, fibrous tissue. This connective tissue helps to maintain the shape of your eyeball, while the conjunctiva is a mucous membrane covering the outer part of your sclera.
Many conditions can affect the conjunctiva. Some are common and cause mild symptoms, while others are rare and can be vision-threatening or even life-threatening. Several of these conditions include:
Conjunctival melanomas can be life-threatening if the cancer spreads to other parts of the body via the lymphatic system.
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