Ptosis is a condition characterized by drooping of the upper eyelids when the eye is open. It may be congenital (present at birth) or occur later in life. It is generally divided into several types that are determined by the cause of the drooping eyelid: Myogenic, Neurogenis, Mechanical, and Involutional.
Myogenic ptosis is usually caused by a muscle disorder. The two muscles responsible for raising the eyelid are the levator muscle and Mueller’s muscle. In some cases the ptosis is a result of all voluntary muscles in the body weakening because of abnormalities in the muscles. Congenital myogenic ptosis is a result of scarred or non-functional eyelid muscles. Some forms of myogenic ptosis respond to medication.
Neurogenic ptosis is caused by abnormal nerve function. The nerve responsible for raising the eyelid is the oculomotor nerve. The eyelid will droop if the oculomotor nerve is damaged. In most cases neurogenic ptosis occurs adventitiously. Diabetes, tumors, aneurysms, strokes and injuries are all conditions that can affect the oculomotor nerve. Mueller’s muscle,which raises the eyelid, is controlled by several nerves known as the sympathetic nerves. Sympathetic nerve damage can cause a minor drooping of the eyelid. Sympathetic nerves travel at the top of the chest cavity; thus, abnormalities in the lungs can lead to ptosis. Malignant tumors in the lungs can also lead to ptosis. Some types of neurogenic ptosis run their course and improve over time.
A third type of ptosis is mechanical. Mechanical ptosis is a result of eyelids that are simply too heavy to lift. Eyelids may become heavy with extra skin, fat, or tumors. Mechanical ptosis can generally be corrected with surgery.
Involutional ptosis develops as a result of the aging process or stretched eyelid tissue when the muscle attatchments to the eyelid degenerate. The nerves and muscles function properly; however, the muscle is no longer fully attached to the eyelid. Although the muscle contracts, the eyelid cannot come up.
Most problems from ptosis can be corrected surgically. The muscles can be shortened to increase pulling strength of the eyelid or can be reattached to the eyelid. In some cases, the eyelids can be raised with tissues attached to the eyebrows ; the lid is lifted when the eyebrow is raised.
Other conditions associated with ptosis are strabismus (improperly aligned eyes), refractive errors, or astigmatism. In most cases ptosis affects visual field but may also result in blurred vision (acuity). Ptosis may be indirectly responsible for serious neck problems when an individual tips his or her head back to see underneath the drooping eyelid. If congenital ptosis blocks any part of the child’s visual field, it must be corrected through surgical procedures as soon as possible. If left untreated, permanent loss of vision may occur as a result of amblyopia (lazy eye). Amblyopia prevents the eye from developing normal vision during early childhood.
Ptosis.- eyelids that droop. Retrieved July 4, 2010, from