PTOSIS (DROOPING EYELIDS)

Ptosis refers to drooping eyelids. This condition can either be present at birth (congenital ptosis) or develop later in life (acquired ptosis). In general, ptosis is divided into several types, determined by the cause of the drooping eyelid. MYOGENIC ptosis means that the lid sags because of a problem with the muscle that raises the eyelid. NEUROGENIC ptosis refers to the condition where the nerve supply to the muscle is affected. MECHANICAL ptosis occurs when the weight of the eyelid is too great for the muscles to lift. INVOLUTIONAL ptosis develops when the muscular connections in the eyelid weaken.

Myogenic ptosis is usually a reflection of a systemic muscle disorder. When the muscles are weakened by disease, they cannot pull the eyelid up into position. The muscles that raise the eyelid are the levator muscle and Muller's muscle. An example of a muscle condition that causes ptosis is MYASTHENIA GRAVIS. This is a disease in which the voluntary muscles in the body weaken due to abnormalities within the muscles, themselves. People with myasthenia gravis will often have drooping eyelids as well as crossed eyes due to imbalance of the muscles that control eye movement. In congenital myogenic ptosis, the eyelid muscles are either scarred or do not work.

Abnormal nerve function causes neurogenic ptosis. The primary nerve responsible for raising the eyelid is the third cranial nerve, the oculomotor nerve. If this nerve is damaged, the eyelid drops. Some of the conditions that can affect this nerve are: diabetes, tumors, aneurysms, strokes and injuries. A secondary muscle that raises the eyelid is Muller's muscle. This muscle is supplied by different nerves called sympathetic nerves. If these nerves are damaged, a milder sagging of the eyelid is present. Because these sympathetic nerves travel at the top of the chest cavity before going up the neck to the head, abnormalities in the upper areas of the lungs can lead to ptosis. The milder ptosis just described is part of a group of abnormalities called HORNER'S SYNDROME. A Pancoast tumor is an example of a type of lung cancer that can lead to this condition.

Mechanical ptosis occurs when the weight of the eyelid is too great for the muscles to lift. Tumors or excess skin and fat can weigh down the eyelid.

Involutional ptosis develops when the attachments of the muscle to the eyelid degenerate. This occurs with aging or with stretching of the eyelid tissues, due to swelling. In this condition, the nerve and muscle work properly. Since the muscle is no longer fully attached to the solid structures inside the eyelid, the muscle contracts but the eyelid does not come up.

Ptosis can usually be corrected. Some forms of myogenic ptosis respond to medication. Some types of neurogenic ptosis get better by themselves. Most ptosis problems are corrected with surgery. Surgery can strengthen the pulling force of the muscles by shortening them. The muscles can be reattached to the eyelid structures. When the muscle fails to work properly, the lid can be suspended with tissues attached to the eyebrow muscles. Then, the lid is lifted by raising the brow.

Most ophthalmologists are trained in eyelid surgery, oculoplastic surgery, and are the preferred surgeons to evaluate and safely correct these conditions without putting the eyes at excessive risk.

Copyright, 1997. Richard E. Gans, M. D.

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