Avoiding Pretarsal Denervation in Lower Blepharoplasty Incisions: Refined Pretarsal Motor Nerve Anatomy

Abstract

Background: Pretarsal atrophy is not uncommonly found in patients who have undergone a transcutaneous or transconjunctival lower blepharoplasty due to intraoperative denervation of the pretarsal orbicularis oculi. The motor supplying concept to the lower eyelid was recently updated, however, there have not yet been any guidelines to preserve motor nerves in lower blepharoplasty incisions based on the refined knowledge. Methods: 46 fresh cadaveric hemifaces were examined to find a safe zone for a lower blepharoplasty muscle incision and a danger zone for an infraorbital incision in the transblepharoplasty midface approach. Additionally, practical anatomy about the pretarsal motor supply was also investigated in detail. Results: The medial, lateral, superior, and inferior borders of the safe zone for a lower blepharoplasty muscle incision were 9.4 mm from the medial canthus line, 3 mm from the lateral canthal crease, and 6.0 and 6.5 mm from the eyelid margin, respectively. The danger zone for an infraorbital incision ranged from 9.4 mm medial to the midpupillary line to 9.7 mm lateral to the midpupillary line. The motor nerve in the danger zone abutted the distal roof of the preseptal pocket making it vulnerable to electrocautery heat. Motor nerve distribution of the lower pretarsal orbicularis oculi was fully identified. Conclusion: There is a safe zone for the lower blepharoplasty muscle incision which if adhered to will preserve the pretarsal motor supply and prevent muscle atrophy. There is an infraorbital danger zone, where surgeons should pay special attention to avoid electrocautery heat injury.