Experimental and clinical data on the insertion of the levator palpebrae superioris muscle.

Radiographic and electron microscopic evidence showed that the upper eyelid skin crease is formed by the insertion of the levator palpebrae superioris muscle into the septa between the orbicularis muscle into the septa between the orbicularis muscle bundles and not into the skin itself. Experiments on monkeys showed that the insertions of the aponeurosis and of Müller's muscle both contribute to normal eyelid elevation. No histologic evidence was found for a disinsertion of Müller's muscle in 20 cases of blepharoptosis. This, with other evidence discussed, supports the functional importance of the human aponeurotic insertions in eyelid elevation.