PTOSIS

drooping of the upper eyelid. The condition may be congenital or acquired. In congenital ptosis, which is frequently hereditary, the muscle that elevates the lid (the levator palpebrae superioris) is either absent or imperfectly developed. The condition is often associated with other abnormalities of the eye muscles and with congenital cataracts (opacity of the lens). Acquired ptosis is usually due to injury or disease of the nerves that control the movements of the levator muscle. In a disorder called Horner's syndrome, ptosis occurs in association with excessive contraction of the pupil and abnormally sunken eyes.