Study on the differences in the pre-tarsal fat-fascia layer tissue structure between congenital single eyelids and double eyelids

LONG Xiren; CHEN Qian; LI Gaofeng; LI Xi; FU Anqi

doi:10.3969/j.issn.1673-7040.2025.09.002

Abstract：Objective To explore the relationship between the pre-tarsal fat-fascia layer and upper eyelid morphology,guiding bionic natural double eyelid reconstruction surgery.Methods From January to September 2021,Department of Dermatology and Cosme-tology,Changsha County People's Hospital investigated the pre-tarsal fat-fascia layer in single and double eyelids through ultrasound imaging,intraoperative observation,cadaver dissection,and histological analysis.(1)Ultrasound observation:An Aplio ultrasound with an 18 MHz probe was used to examine 58 volunteers(116 eyelids),divided into Group A(congenital single eyelids,58 eyes)and Group B(congenital double eyelids,58 eyes).Ultrasound images were analyzed to observe the pre-tarsal fat-fascia structure.Measurements were taken at three points.Point a:Intersection of the pupillary midline and double eyelid line(7 mm from the eyelid margin in single eyelids).Point b:Midpoint between Point a and the lateral canthus on the double eyelid line.Point c:Midpoint between the double eyelid line and medial canthus.The thickness and layering of the pre-tarsal fat-fascia layer were recorded.(2)Intraoperative observation:86 eyelids(Group A:47 single eyelids;Group B:39 double eyelids)were analyzed during surgery.Structural differences and volume of the pre-tarsal fat-fas-cia layer were measured.(3)Cadaver dissection and histological observation:Six cadaver heads(Group A:3 single eyelids;Group B:3 dou-ble eyelids)were dissected.Gross observation was performed on one side of the bilateral eyelids,and specimens were taken from the other side for HE and Masson staining observation.Results(1)Ultrasound observation:Both groups exhibited a two-layered pre-tarsal fat-fas-cia structure:a superficial loose fat-fascia layer(hypoechoic)and a deep dense fascia layer(hyperechoic).The dense layers of the double eyelid and the single eyelid were closely attached to the surface of the tarsal plate and were very thin,and there is no statistically significant difference(P＞0.05).Thickness of loose fat fascia tissue:In group A,the thickness at Point a was(1.03±0.34)mm,the thickness at Point b was(2.43±0.79)mm,and the thickness at Point c was(2.53±0.49)mm.In group B,the thickness at Point a was(0.88±0.14)mm,the thickness at Point b was(2.06±0.76)mm,and the thickness at Point c was(1.82±0.45)mm.The thickness of the three points in group A was all higher than that in group B(P＜0.001).(2)Intraoperative observation:Both groups showed a layered structure.The loose layer in Group A was thicker and continuous with the retro-orbicularis oculi fat(ROOF),while the dense layer connected to the orbital septum and levator aponeurosis.After removal,the loose layer volume in Group A[0.06(0.04～0.07)ml]exceeded Group B[0.04(0.03～0.05)ml](P＜0.001).(3)Cadaver and histological observations:Gross dissection revealed continuity between the pre-tarsal loose fat-fascia layer and ROOF.HE staining confirmed two layers:a loose layer(fat and sparse connective tissue)and a dense layer(tightly adhering to the tarsal plate).Group A had a thicker loose layer.Masson staining showed the dense layer comprised dense fibrous connective tissue with abundant vasculature,while the loose layer contained fat and minimal fibrous tissue.Conclusion The pre-tarsal fat-fascia layer in single and dou-ble eyelids consists of superficial loose and deep dense layers.The loose layer may critically influence double eyelid formation.Manipulat-ing the pre-tarsal loose fat-fascia layer may aid in shaping a bionic double eyelid.