Detailed anatomy of the transverse superior fascial expansion of the upper eyelid

Purpose: This study was designed to elucidate the detailed anatomy of the transverse superior fascial expansion (TSFE) and its relationship to the superior rectus muscle (SRM) and the levator palpebrae superioris (LPS). Methods: In this cohort study, 46 eyes of 23 cadavers were observed macroscopically. Dissection from the SRM origin to its insertion was performed, and the width, length, and tensile strength of the TSFE were determined. Results: The TSFE was located between the LPS and SRM. It originated at the surface of the SRM, 32.75 ± 4.40 mm from the origin of the SRM, and extended anteriorly. The TSFE firmly adhered to the SRM surface, 1.53 ± 0.47 mm medially and 1.19 ± 0.19 mm laterally, extended upwards and anteriorly, and inserted to the under surface of the LPS. The TSFE width was 6.70 ± 1.17 mm at the origin site on the SRM surface and 11.42 ± 6.70 mm at the insertion site on the LPS under the surface. Its total length was 11.67 ± 0.87 mm medially and 11.55 ± 0.94 mm laterally The TSFE was first encountered 11.49 ± 1.17 mm laterally and 11.57 ± 1.27 mm medially from the SRM insertion on the SRM’s anterior surface. The tensile strength of the TSFE was significantly greater than that of the intermuscular fascia between the SRM and LPS (9.74 ± 4.53 N vs 3.02 ± 1.85 N, P =0.001). Conclusions: This study provides a good understanding of the TSFE structures conducive to performing SRM surgery.