Histological changes in congenital and acquired blepharoptosis.

Histological specimens of eyelids from patients with congenital genuine ptosis and acquired involutional ptosis are compared. In congenital ptosis there is evidence of true muscular dystrophy of the levator muscle as demonstrated by: loss of cross striations, random decrease in muscle fibre diameter, sarcolemmal retraction, nuclei alignment, and fibrous and fatty tissue displacement of the striated fibres. In involutional ptosis disinsertion of the levator aponeurosis from its normal insertion on the inferior-anterior surface of the tarsus is demonstrated. Correlation between clinical presentation and surgical correction is explained in light of these findings.