Ptosis is a dropping or drooping of the upper eyelid from a weakness or paralysis of the muscles. The normal position of the upper eyelid is midway between the superior limbus and the upper pupillary margin. Another name for this condition is blepharoptosis.

Ptosis may be congenital or acquired, and is usually hereditary. The types of pstosis as classified by their etiology are as follows:

• Levator maldevelopment results from dystrophy of the levator muscle, affecting both contraction and relaxation of fibers.

• Myogenic ptosis includes blepharophimosis; external ophthalmoplegia; myotonic dystrophy; congenital fibrosis of the extraocular muscles; and myasthenia gravis.

• Aponeurotic ptosis occurs following ocular surgery, and trauma.

• Neurogenic ptosis evidenced by the opening of the eye when the jaw opens because the trigeminal nerve and oculomotor nerve both innervate the levator muscle.

• Mechanical ptosis characterized by a scar or tumor that may prevent the upper lid from opening.

• Apparent ptosis indicated by a downward deviation of the eye giving the appearance of ptosis.

A drooping upper eyelid is present in the primary position of gaze, and there is limited movement on the upgaze and impaired lid closure on the downgaze.

Tests that may be used include: visual acuity; visual fields; ocular motility; alignment testing; extraocular movement testing; ophthalmoscopy; slit lamp; tonometry; and computed tomography (CT) scan.

All types of ptosis are treated surgically with the exception of myasthenia gravis.

The goal of surgery is symmetry. This goal is possible if the levator muscle function is unimpaired. Those with little or no levator function require a more complex type of surgery.

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