Structural abnormalities in the levator palpebrae superioris muscle in patients with congenital blepharoptosis.

BACKGROUND AND OBJECTIVE

To evaluate structural and ultrastructural abnormalities of the levator palpebrae superioris (LPS) complex in patients with congenital blepharoptosis.

PATIENTS AND METHODS

Samples of the LPS complex were obtained from patients operated on for congenital blepharoptosis between 2000 and 2001 and studied under light microscopy (15 cases) and electron microscopy (9 cases).

RESULTS

Findings of light microscopy evaluation of the LPS complex correlated closely with the clinical grading of congenital blepharoptosis-hypoplasia, decreased number and varying diameter of muscle fibers, and fibrous tissue hyperplasia in the endomysium and perimysium. The Müller's muscle preserved a normal appearance. Mild blepharoptosis revealed proliferation of collagen fibers on electron microscopy. Moderate blepharoptosis showed abnormal distribution of myofibrils and distortion of the tubular system and mitochondria in addition to the changes observed in mild blepharoptosis. Severe blepharoptosis showed mitochondria loss, cytoplasm thinning, and homogenous fiber areas in addition to the changes observed in mild and moderate blepharoptosis.

CONCLUSIONS

The clinical degree of severity of congenital blepharoptosis correlates positively with the degree of histopathologic changes in the levator palpebrae superioris muscle.