Upper Eyelid Anatomy Revisited based on Detailed Operating Microscope Observations.

This anatomical study of the upper eyelid is based on detailed analysis of 74 consecutive primary upper blepharoplasty procedures (148 eyelids) performed under the operating microscope. There were 54 Asian and 20 Caucasian patients. Visualization under the miscroscope provided a unique operative perspective on the structural anatomy and relationships of the upper eyelid. The anatomy of the orbital septum and its relationships to the retro-orbicularis oculi fat (ROOF), levator aponeurosis, and retroseptal fat pads are presented in detail. The lower-positioned transverse ligament, its relationship to the anterior fascial sheath of the levator aponeurosis and the bilaminar nature of the levator aponeurosis, consisting of anterior and posterior layers, were clearly demonstrated. The lower-positioned transverse ligament was identified in 94% of eyelids. The mean length of the levator aponeurosis was 17.6 mm (range, 14-21 mm), and the mean length of its fused proximal portion was 5.4 mm (range, 4.0-8.0 mm). The clinical relevance of these anatomical findings in upper blepharoplasty is discussed. An anterior approach to the Müller muscle and its dissection is also presented. Finally, danger zones for bleeding are detailed with videographic demonstration. This paper provides a clearer surgical roadmap, offering practical anatomical guidance for various cosmetic and reconstructive upper eyelid procedures.