Pathogenesis and surgical correction of dynamic lower scleral show as a sign of disinsertion of the levator aponeurosis from the tarsus

Abstract

The purpose of this study was to confirm whether lower scleral show is caused by the disinsertion of the levator aponeurosis from the tarsus. Aponeurotic advancement by vascular clips or by surgery involving the orbital septum significantly lowered the global position in the orbit and significantly diminished the degree of retraction of the lower eyelid, resulting in satisfactory improvement of lower scleral show in 100 patients with various aponeurotic blepharoptosis. Therefore, we propose the pathogenesis of lower scleral show as follows: additional contraction of the levator muscle to compensate for the disinsertion of the levator aponeurosis from the tarsus for maintenance of an adequate visual field is accompanied by additional contraction of the superior rectus muscle through the strong intermuscular fascia, resulting in upward rotation of the globe. To maintain the horizontal visual axis and foveation without inclination of the head in the primary gaze position, additional contraction of the inferior rectus muscle is induced, which pulls upon the inferior suspensory ligament of Lockwood and the capsulopalpebral fascia. The former displaces the globe upwards and the latter retracts the lower eyelid, resulting in dynamic lower scleral show as a sign of disinsertion of the levator aponeurosis from the tarsus, which can be surgically corrected.