A drooping eyelid is also called ptosis or blepharoptosis. In this condition, the border of the upper eyelid falls to a lower position than normal. In severe cases, the drooping eyelid can cover all or part of the pupil and interfere with vision.
Ptosis can affect one or both eyes. It may be present at birth (congenital ptosis), or it may develop gradually over decades. Sometimes ptosis is an isolated problem that changes a person's appearance without affecting vision or health. In other cases, however, it can be a warning sign that a more serious condition is affecting the muscles, nerves, brain or eye socket. Ptosis that develops over a period of days or hours is more likely to signify a serious medical problem.
Some of the causes of ptosis include:
Congenital ptosis — In this condition, an infant is born with ptosis because of a developmental problem involving the muscle that raises the upper eyelid (levator muscle). In approximately 70% of cases, the condition affects only one eye. If the drooping eyelid obscures part of the baby's visual fields, surgery must be done to correct the problem early in life to prevent permanent loss of vision.
Aponeurotic ptosis (senile or age-related ptosis) — Aging is the most common cause of ptosis that is not present at birth. In senile ptosis, the long-term effects of gravity and aging cause stretching of a wide, tendon-like tissue that helps the levator muscle lift the eyelid. Although both eyes usually are affected, drooping may be worse in one eye.
Myasthenia gravis — Ptosis can be one of the first symptoms of myasthenia gravis, a rare disorder that affects the ways muscles respond to nerves. Myasthenia gravis can cause progressive muscle weakness, not only in the eyelids but also in the facial muscles, arms, legs and other parts of the body.
Muscle diseases — Ptosis can be a symptom of an inherited muscle disease called oculopharyngeal muscular dystrophy that affects eye motion and can cause difficulty swallowing. In younger adults, ptosis can be caused by a group of muscle illnesses called progressive external ophthalmoplegia, which cause ptosis in both eyes, problems with eye movement, and sometimes other muscle symptoms that involve the throat or heart muscle.
Nerve problems — Because the eye muscles are controlled by nerves that come from the brain, conditions that injure the brain or its cranial nerves sometimes can cause ptosis. These conditions include stroke, brain tumor, a brain aneurysm (a grapelike swelling on a blood vessel inside the brain), and nerve damage related to long-term diabetes. Another cause of ptosis is Horner's syndrome, which also can cause an abnormally small pupil and loss of the ability to sweat — on half the face. One particularly dangerous cause of Horner's syndrome is a cancerous tumor located at the top portion of the lungs.
Local eye problems — In some cases, an eyelid droops because of an infection or tumor of the eyelid, a tumor inside the eye socket, or a blow to the eye.