INTRODUCTION Blepharoptosis, or ptosis, is a drooping of the upper eyelid such that the eyelid margin rests lower with respect to the superior corneal limbus. There are numerous causes for ptosis and these can be classified according to mechanistic etiologies. Aponeurotic ptosis is caused by defects in the levator aponeurosis, either redundancy or frank disinsertion. This can be seen from trauma or surgery, or as an involutional phenomenon which is the most common form of adult acquired ptosis. Myogenic ptosis results from myopathic or myogenic diseases affecting the levator muscle. It most commonly occurs as a congenital developmental defect, but can be associated with chronic progressive external ophthalmoplegia, myotonic dystrophy, oculopharyngeal dystrophy, myasthenia gravis, trauma, or toxins. In neurogenic ptosis there is an interruption of nervous innervation to the levator muscle. Etiologies include vascular lesions, ischemia, multiple sclerosis, toxins, infections, tumors, and trauma. Depending upon the site of neural injury there may be an associated palsy of other extraocular muscles innervated by the oculomotor nerve. Also included in this group are the so-called synkinetic syndromes such as the Marcus Gunn Jaw Wink, and misdirected third nerve fibers. Horner's syndrome resulting from loss of sympathetic innervation to Muller's accessory sympathetic muscle is also grouped under the neurogenic ptoses. Mechanical ptosis refers to a physical restriction to eyelid opening by an orbital or eyelid mass or scarring.
CLINICAL PRESENTATION In all forms of ptosis the eyelid margin lies more than two millimeters below the superior corneal limbus. The condition may be unilateral or bilateral. The ptosis may be mild or severe, and often results in significant loss of superior visual field. In severe bilateral congenital myogenic ptosis a backward head tilt is often seen. Levator muscle function is typically good to excellent (8 or more mm) in aponeurotic, but is usually reduced in myogenic or neurogenic ptosis. In unilateral aponeurotic ptosis the degree of lid droop in the affected eyelid remains constant with respect to the normal opposite eye in all positions of vertical gaze. Typically, the ptosis becomes worse at night or when the patient is tired. In unilateral myogenic ptosis the degree of lid droop increases in upgaze, but decrease in downgaze or the affected lid may even be relatively retracted. This is because of fibrosis of the levator muscle that does not contract or stretch very well. Mechanical ptosis is usually associated with eyelid scars or masses, or with concurrent orbital disease.
TREATMENT The goal of treatment for ptosis is to elevate the eyelid margin to a more normal position and to restore superior visual field. When levator muscle function is good or excellent correction simply requires a tightening or reattachment of the aponeurosis to the tarsal plate. This is achieved through a skin or transconjunctival incision. Surgery is best performed under local anesthesia to allow for patient cooperation in elevating the lid during surgery. When levator muscle function is only fair (5-8 mm) aponeurotic advancement alone will usually be inadequate. Shortening of the levator muscle above the level of Whitnall's ligament will allow greater degrees of shortening and a better result. For poor levator function cases (4 mm or less), the only reliable method of elevating the lid is with a frontalis suspension procedure using a silicone rod or other suspensory material.
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