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Holmdel, NJ 07733
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Pertinent Eyelid Anatomy

The eyelids and tissue around the eye constitute a very delicate and complex arrangement. Beginning from the skin surface the layers of the eyelid from outside to inside are as follows–
The orbicularis muscle surrounds the eye in a circular fashion in both the upper and lower eyelids. The orbicularis muscle is responsible for closing the eye. The orbicularis muscle is therefore very important in the blink mechanism and closing the eye for protection.
In the upper lid is the levator muscle. The levator muscle begins deep behind the eye and fans out in the upper eyelid to eventually attach to the tarsal plate and skin. The levator muscle is primarily responsible for elevating the upper eyelid. As you can see two different muscles work to open and close the upper eyelid. Another muscle that has a small role in elevating the upper eyelid is Muller’s muscle. This muscle becomes more important in patients with thyroid eyelid problems. In the lower eyelid, one finds the capsulopalpebral fascia, a retractor of the lower eyelid. This fascia is analogous to the levator muscle of the upper eyelid.
The tarsal plate is a cartilaginous structure that gives support to the upper and lower eyelids. It is only in a portion of the eyelid. Without the tarsus, the eyelid would be very floppy. Within the tarsal plate are many oil producing glands called meibomian glands. The meibomian glands serve a vital function in maintaining the proper moisture in the eye. A blockage in these glands to one of the most common eyelid infections called a chalazion. A chalazion is sometimes confused with a stye.
Attached to the tarsus is the orbital septum. The orbital septum is a fine membrane that inserts into the tarsus and the bony rim around the eye. This structure keeps the orbital fat from protruding and creating unsightly “bags”. The orbital fat surrounds the eye and acts like a “shock absorber” to protect the eyeball in case of injury.
Lining the inside of the eyelid and in contact with the eyeball is the conjunctiva. The conjunctiva is called a mucous membrane because it provides lubricating functions for the eye and eyelid.
The two corners of the eyelid where the upper and lower eyelids meet are called the canthi. The lateral canthus is located at the outer corner and the medial canthus is located at the inner corner.
The eyelid margin is where the upper and lower eyelids “end”. The eyelid margin goes from one canthus to the other and is located at the level of the eyelashes. The distance between the upper eyelid margin and the lower eyelid margin defines how “opened “ the eye is. This is called the palpebral fissure.
The eyebrows have a number of muscles that work to depress and one basic elevator. The corrugator and procerus muscles primarily depress the brow. Simply speaking these muscles are located between the brows. The corrugator and procerus muscles are the main muscles treated with botox for glabellar frowns. The main elevator of the brow is the frontal muscle. Contraction of this muscle can cause excessive forehead lines and is frequently treated with botox.

Lacrimal System

The tear duct or lacrimal drainage system is composed of two small openings, one in the upper eyelid and one in the lower eyelid. These are located near the medial canthus and are called the lacrimal punctum. They are small openings in the lid and constitute the beginning of the drainage apparatus. From the puncta the tears enter a narrow tube called the canaliculus. The canaliculi from the upper lid and lower lid connect together and drain into a reservoir called the lacrimal sac. From the lacrimal sac, the tears drain down a bony canal on the inside of the nose and eventually empty into the nose and are swallowed. All this happens without one being aware of the process.
Tears are produced by the lacrimal gland located under the upper eyelid in outer part above the lateral canthus. Tears therefore have to travel from the upper outer area of the eye to the inner or medial canthus in order to go down the drainage system. This is accomplished by the active contractions of the eyelid muscles with each blink. Thus the blink mechanism is very important to help distribute the tears.

Copyright © 2009 Atlantic Eye Physicians