Levator sheath revisited

Abstract

The aim of this study was to reconfirm the detailed histologic structure of the levator aponeurosis and superior transverse ligament, which were first described by Whitnall. Twenty-eight upper eyelids from 28 Korean adult cadavers (mean age, 79.5 [SD, 11.3] years; 16 males and 12 females) were used. Sagittal sections on the midpupillary line were made, and 10-μm-thick sections were prepared. Twenty-five were stained with Masson trichrome, and 16 were prepared for immunohistochemical staining for smooth muscle fibers using mouse monoclonal anti-smooth muscle Ab. The levator palpebrae superioris muscle was covered with its fascial sheath along its course. The superficial part of the fascia sheath that covered the upper aspect of the levator palpebrae superioris just behind the aponeurosis was condensed to form a definite ligamentous band. In front of this ligamentous condensation, the sheath becomes abruptly so thin that it appears to end in a free border, but it could be traced forward as a very delicate layer up to the supratarsal border. The orbital septum consisted of 2 layers. The whitish outer (superficial) layer descends to interdigitate with the levator aponeurosis with loose connective tissue, and then it disperses inferiorly. The inner (deep) layer initially follows the superficial one, and then it reflects at the levator aponeurosis and continues posteriorly with the levator sheath. In most of the specimens, the levator aponeurosis consisted of a single layer in 27 (96.4%) of 28 eyelids. Only 1 eyelid has been observed to show a double-layered levator aponeurosis (3.6%). Some immunostained smooth muscle fibers in the lower side of the levator aponeurosis ran along its entire course. We reconfirmed the levator sheath covering the levator aponeurosis, and it continued anteriorly with the inner layer of the orbital septum, as Whitnall described. This information will be helpful when performing upper eyelid surgeries.