Not Merely an Enveloping Membrane: Anatomy of the Preaponeurotic Fat Membrane and Its Role in Blepharoptosis Correction.

[BACKGROUND] In blepharoplasty, a preaponeurotic fat pad has been considered to provide padding and structural support for the eyelid. In our practice, we have identified a dense fibrous membrane surrounding the preaponeurotic fat pad, which can transmit the uplift force of the levator muscle.

[OBJECTIVES] As the preaponeurotic fat pad and its relationship with the surrounding layers remain controversial, this study aims to determine the histological characteristics of the preaponeurotic fat pad and to introduce a procedure involving the advancement of the posterior layer of the preaponeurotic fat membrane in blepharoptosis correction.

[METHODS] This retrospective study enrolled 42 eyes from 28 blepharoptosis patients who underwent a preaponeurotic fat membrane advancement procedure with or without levator aponeurotic advancement between October 2020 and June 2023. Six cadaveric upper eyelids from three fresh cadaver heads were harvested for histological examination, and one formalin-treated cadaver head was used for macroscopic anatomic evaluation.

[RESULTS] The mean preoperative MRD1 was 1.89 ± 0.89 mm. Among the forty-two upper eyelids, thirty-six underwent advancement of the preaponeurotic fat membrane. The other six upper eyelids had inadequate correction after performing the levator aponeurosis advancement, and therefore, a combined preaponeurotic fat membrane advancement was performed. Nine patients reported lagophthalmos during the first three months postoperatively, but this condition significantly improved by six months postoperatively. In anatomic evaluation, multilayered fibrous tissue structures were identified in and around the preaponeurotic fat pad.

[CONCLUSIONS] Based on our clinical observations and anatomical studies, we believe that this fibrous envelope can be used to correct mild-to-moderate ptosis. The indications for this procedure range from mild-to-moderate ptosis. It can be used alone in patients with mild- or pseudo-ptosis due to overloading of the upper eyelid, or it can be used in conjunction with levator aponeurosis advancement in patients when the procedure is insufficient to achieve a proper correction.

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