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Ptosis
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.
References:
Ptosis.- eyelids that droop. Retrieved July 4, 2010, from
http/www.allaboutvision.com/conditions/droopinglids.htm
Ptosis. Retrieved July 4, 2010, from
http/www.asoprs.org/files/public/infoptosis.pdf
Ptosis. Retrieved July 4, 2010, from
http/www.nim.nih.gov/../001018.htm
Ptosis. Retrieved July 4, 2010, from
http/www.tsbvi.edu/..ptosis.htm
Ptosis. Retrieved July 4, 2010, from
http/www.emedicine.medscape.com/conditions/ptosis/index.cfm