Histological analysis of the lower-positioned transverse ligament

Abstract

The lower-positioned transverse ligament (LPTL) had been thought to run parallel to the junction between the orbital septum and the levator aponeurosis (junction). However, its true course was disclosed as crossing the junction. Since earlier histological studies were undertaken before the precise course was elucidated, it was uncertain whether the true LPTL was adequately disclosed. Therefore, we examined ten upper eyelids of 6 Asian patients who underwent blepharoptosis repairs. The LPTL and the tissue running parallel to the junction were harvested intraoperatively. Light-microscopically, the LPTL contained looser and thinner collagen bundles and less elastic fibres than the parallel tissue. Electron-microscopically, collagen microfibrils in the LPTL had almost the same periodicity and thickness as those in the parallel tissue. The LPTL is a loose and inelastic structure, which at a light microscopic level is completely different from the parallel tissue; however, the differences could not be verified by electron microscopy.

Fig. (1)

Modified course of the lower-positioned transverse ligament (LPTL) (top: superior; left: medial). Reprinted with permission of the Japanese Journal of Ophthalmology (Kakizaki H, et al. Posterior aspect of the orbital septum is reinforced by ligaments. Jpn J Ophthalmol 2005; 49: 477-80). The LPTL originates from the trochlea and runs in an inferolateral direction. The LPTL passes over the junction between the orbital septum and levator aponeurosis, attaches onto the posterior aspect of the orbital septum, and runs towards the lateral orbital rim. The LPTL was harvested in the part that the arrow indicates. Tr, trochlea; Jun, junction of the orbital septum and the levator aponeurosis; LA, levator aponeurosis; LG, lacrimal gland; MTL, medial horn tensing ligament; OS, orbital septum; Lig, ligaments on the posterior aspect of the orbital septum; PO, periosteum.

Fig. (2)

Light microscopic findings. (A) Lower-positioned transverse ligament. Collagen bundles are scattered and thin. (B) The parallel tissue on the junction between the orbital septum and the levator aponeurosis. Thick collagen bundles with a few elastic fibres congregate.

Fig. (3)

Transmission electron microscopic findings. (A) Lower-positioned transverse ligament. (B) The parallel tissue on the junction between the orbital septum and the aponeurosis. Both tissues contain microfibrils with the same periodicity and thickness.