Histologic Findings of the Levator Muscle in Ptosis

ABSTRACT

The authors have studied 67 biopsy specimens of the levator muscle, obtained from the external levator resection for ptosis of 50 patients. Atrophy marking as 3+ and complete absence of the levator muscle fiber were predominating in the specimens of severe congenital ptosis or ptosis with poor levator funtion. The degree of levator muscle atrophy seemed to be related with levator function. Fibrosis and fatty infiltration of the levator muscle and Muller's muscle were examined frequently in the specimens with severe atrophy of muscle fibers. On histochemical detection of muscle fibers using ATPase stain, lightly stained Type I fibers of the levator muscle were larger in amount than darkly stained Type II fibers and atrophy of the two fibers was similar in degree. Muller's muscle fibers were evenly stained with positive ATPase reaction but slightly lighter than Type II fibers.