Palpebral ptosis means eyelid drooping. The amount of eyelid drooping is the difference in millimeters between the normal level and the existing level while looking in primary position. It can be estimated accurately evaluating the relation of the lid margin both to upper limbus and to the upper pupillary border. Normally the lid margin should overlap the upper limbus by about 2 mm. Ptosis can be divided into large groups: congenital and acquired.
CONGENITAL PTOSIS
SIMPLE CONGENITAL PTOSIS: developmental dystrophy of the levator muscle of unknown cause, It usually is unilateral. Surgical treatment between 3 and 4 years of age prevent amblyopia. Levator recession if levator function is acceptable or brow suspension if levator function is poor, are the tratment of choice.
CONGENITAL PTOSIS IN PALSY OF THIRD CRANIAL NERVE: the strabismus must be corrected before the ptosis.
MARKUS GUNN JAW-WINKING SYNDROME: it is caused by abnormal levator innervation.
BLEPHAROPHIMOSIS SYNDROME: is a congenital form which may include varying degrees of telecanthus,epicanthus,ectropion of the lower eyelids, a flat glabella,and “lop-ears” in its characterists. The treatment depends on the degree of blepharophimosis.
ACQUIRED PTOSIS
Acquired ptosis can be divided in four categories: neurogenic, myogenic, traumatic and mechanical.
– NEUROGENIC PTOSIS: caused by oculomotor nerve injury or disease,or by injury to or disease of the sympathetic nerve supply to Muller’s muscle. In this group can be includes also the ptosis of multiple sclerosis,cases caused by neurotoxin, such as botulism, heavy metal poisoning.
– MYOGENIC PTOSIS: caused by abnormalities of the levator muscle or its tendon. It includes myasthenia gravis ptosis (the abnormality exists at the myoneuronal junction) and chronic progressive external ophthalmoplegia. The major part are caused by disinsertion of the levator aponeurosis from its attachment to the anterior surface of the tarsus, or by thinning and degeneration of the levator aponeurosis.
– TRAUMATIC PTOSIS: includes cases caused by head or orbital injures by damaging the oculomotor nerve, or by wounds of the eyelid that damage the levator aponeurosis or muscle. They require meticulous reconstructive surgery to bring about satisfactory functional and cosmetic results.