Junctional variations of the levator palpebrae superioris muscle, the levator aponeurosis, and Müller muscle in Asian upper eyelid

Abstract

Purpose: To examine the junctional variations of the levator palpebrae superioris (LPS) muscle, the levator aponeurosis, and Müller muscle in Asians. Methods: Postmortem specimens of 17 upper eyelids and orbits of 13 Asians (9 right and 8 left; average age, 78.5 years old) were used. Full-thickness sagittal sections of the central part of the upper eyelids and orbits were microscopically examined using Masson trichrome staining. Results: Peripheral branching of the LPS muscle was demonstrated in 12 specimens. Five of these showed that the complete origin of Müller muscle was from the inferior branch, whereas the levator aponeurosis originated from the superior branch. In the other 7 specimens, part of the Müller muscle origin was from the orbital smooth muscle network. The superior branch was significantly thicker (average: 340.8 µm) than the inferior branch (average: 247.5 µm) (p = 0.014). Two specimens did not demonstrate any branching structures, and most areas of the distal end of the LPS muscle was connected to Müller muscle. The other 3 specimens also did not demonstrate these branching structures, and Müller muscle was seen originating from the orbital smooth muscle network and from the inferior aspect of the LPS muscle. Conclusions: The authors demonstrated variations of the junctional anatomy of the LPS muscle, the levator aponeurosis, and Müller muscle. These new anatomical findings may help better understanding of the anatomy of the upper eyelid and the relations to the orbital smooth muscle network.