Ultrasound‐based histological differences of pretarsal fat fascia before and after double eyelid blepharoplasty with the orbital septum method

To observe the changes of pretarsal fat fascia histological structure after double eyelid blepharoplasty with the orbital septum method.

Results: Ninety-eight patients who underwent double eyelid blepharoplasty with the orbital septum method met the inclusion criteria.All 98 patients aged 22.88 ± 3.00 years, including 7 males and 91 females, followed up for 6-12 months.Included 98 volunteers with congenital double eyelid, aged 23.58 ± 2.59 years, including 49 males and 49 females.Ultrasound showed that the pretarsal fat fascia was divided into two layers.The dense layer adhered closely to the surface of the tarsus with no statistically significant differences.There was a statistically significant difference in the thickness of the pretarsal loose fat fascia layer between Group A and B. The points a b c in Group A were significantly thicker than those in Group B and C, and there was no significant difference between Group B and C. Postoperative evaluation: 83 cases were satisfied, 11 cases were basically satisfied and 4 cases were unsatisfied.

Conclusion:
After double eyelid blepharoplasty using orbital septum, the histological structure of pretarsal fat fascia is similar to that of congenital double eyelid, suggesting that double eyelid blepharoplasty with the orbital septum method can change the structure of pretarsal fat fascia and make it similar to congenital double eyelid, which is one of the anatomical bases for its good clinical effect.

K E Y W O R D S
blepharoplasty, histological differences, orbital septum, pretarsal fat fascia, ultrasound in the past and can be regarded as a classic method.We have used this method for more than 10 years, but we have also found some shortcomings.Therefore, in 2015, we began to use a new method of orbital septum reversal and downward fixation to reconstruct a bionic and natural double eyelid.On the one hand, we removed loose pretarsal fat fascia, retain the orbicularis oculi muscle under the incision and the dense anterior tarsal fascia close to the tarsal plate, then covered tarsus with orbital septum flap to form a tight tissue structure in front of tarsus.On the other hand, we used orbital septum flap to connect levator palpebrae superioris aponeurosis, and the pretarsal muscle and skin to reconstruct double eyelid with direct power, which makes the double eyelid flexible.This new method is called orbital septum double eyelid plasty, 3 and achieved good clinical results.
In clinical operation, we also observed the existence of pretarsal fat layer and there was a significant difference between single eyelid and double eyelid, but there are few studies on the pretarsal fat layer at present, and there are many controversies about whether to remove this layer during double eyelid blepharoplasty.For this question, we got the answer by observing and comparing the differences between single eyelid and double eyelid at pretarsal fat layer.Ultrasound is a non-invasive examination method. 46][7] In order to objectively evaluate the effect of removing loose pretarsal fat fascia and orbital septum double eyelid blepharoplasty, we conducted preoperative and postoperative research on congenital single eyelid patients who underwent double eyelid blepharoplasty with the orbital septum method at the Plastic and cosmetic surgery department of Hunan provincial people's hospi-

| Ultrasound imaging
Observe eyelid of preoperative and postoperative patients with congenital single eyelid who underwent double eyelid blepharoplasty with the orbital septum method and congenital double eyelid volunteers by Aplio 18 MHz ultrasonic probe (PHILIPS ELITE), then obtain ultrasound images to observe the histological differences of pretarsal fat fascia before and after double eyelid blepharoplasty with the orbital septum method.We defined three points before observation marked a, b, c. (Figure 3).
The patients and volunteers took the half-lying position and lightly closed the eyelid probe to try to fit the eyelid well while avoiding compressing the eyelid.Observe the main histological structure of the normal eyelid; distinguish the skin, orbicularis oculi muscle, pretarsal fat fascia; measure the thickness of pretarsal fat fascia at each point.

| Surgical methods
First, remove the pretarsal loose orbital fat and fascial tissue, while preserving the orbicularis oculi muscle under the incision and the dense anterior tarsal fascia close to the tarsal plate; and remove the loose fat fascia tissue under the orbicularis oculi muscle under the incision.Next, the orbital septum is horizontally incised, and the lower orbital septum is flipped downwards at its fusion point with the levator palpebrae superioris fascia, forming an orbital septum flap.The flipped-down orbital septum is then sutured and fixed to the orbicularis oculi muscles and the pretarsal fascia.Finally, a 7-0 nylon thread was passed through the orbital septum and anterior fascia of tarsal plate to suture the skin and orbicularis oculi. 3,8The surgical operation is shown in Supplemental Video File S1.

| Effect evaluation
Follow-up from 6-12 months after operation, observed the double eyelid morphology by ultrasound and photograph, and the incision scar was evaluated.The evaluation criteria are as follow: Satisfactory: the shape of double eyelid appeared natural and smooth, with appropriate width and length, and bilaterally basically symmetrical; Basically satisfactory: the shape of both eyelids appeared natural and smooth, but there are visible asymmetric in width or length, and the incision scars were slightly raised or depressed, but further repair surgery was not needed.Unsatisfactory: The shape of double eyelid fold was poor, with obvious bilateral asymmetry, and the incision scar has obvious bulge and depression, which needs to be repaired again.

| Statistical analysis
All statistical analyses were performed using SPSS22.0statistical software, T-test was used to compare the data between multiple groups, the data before and after operation by paired-sample-T-test.
p-values <0.05 were considered statistically significant.Data were presented as mean ± standard deviation (M ± SD).

| RE SULTS
Finally, this study included 98 patients after applying inclusion and exclusion criteria, All 98 patients aged 22.88 ± 3.00 years, including 7 males and 91 females, followed up for 6-12 months.And included 98 volunteers with congenital double eyelid, aged 23.58 ± 2.59 years, including 49 males and 49 females.

| Ultrasound imaging
Ultrasonic images can clearly distinguish the pretarsal anatomical layers.In the orbital septum double eyelid blepharoplasty preoperative group (Figure 4A), postoperative group (Figure 4B), and congenital double eyelid group (Figure 4C In Group C (98 eyes), The thickness of point a was 0.88 ± 0.13 mm; point b is 2.07 ± 0.40 mm; point c is 1.82 ± 0.40 mm.After statistical analysis of the data of each point, there was a statistical difference between Group A and Group B in the thickness of pretarsal loose fat fascia layer.Each point of Group A was significantly thicker than that of Group B (Table 1).There was no statistical difference between Group B and Group C in the thickness of pretarsal loose fat fascia (Table 2).There was significant difference between Group A and Group C in the thickness of pretarsal loose fat fascia (Table 3).

| Postoperative effect
Ninety-eight patients were follow-up for 6-12 months.The surgical results were rated as satisfactory by 83 patients and basically satisfactory by 11 patients, Postoperative double eyelid folds and shape appeared natural and smooth, with appropriate width and length, and bilaterally basically symmetrical, the incision scar thin flat and imperceptible, no upper eyelid retraction eyelid and patients are satisfied (Figure 5).The surgical results were rated as unsatisfactory by four patients, unilateral double eyelid fold be-  There was significant differences between Group A and B. Each point of Group A was significantly thicker than that of Group B.
folds, and all of them achieved basically satisfactory results after reoperation.

| DISCUSS ION
Double eyelid blepharoplasty with the orbital septum method is a kind of blepharoplasty conceived by our team in clinical operation and involves using the orbital septum to reconstruct the close tissue structure of physiological double eyelids, with a direct power aponeurosis to form a direct power, and adjust muscle strength to make double eyelids flexible. 3,8trasound is a non-invasive examination method.0][11] In this study, we used Aplio ultrasound 18 MHz probe (PHILIPS ELITE) to clearly observe the upper eyelid at all levels in front of tarsus.We

[
Correction added on 15th Aug 2023 after first online publication: Fourth author's name and affiliation has been added in this version.] 1 | INTRODUC TI ON Double eyelid blepharoplasty is the most common operation in cosmetic surgery. 1 With the improvement of people's aesthetic requirements, reconstructing bionic and natural double eyelid has become the goal of double eyelid plasty.In 1963, Boo-Chai 2 proposed that partial excision of the orbicularis oculi muscle and fascia resulted in the difference between the upper and lower tissues of the double eyelid line, so that the skin in front of the orbicularis oculi muscle forms an adhesion with the deep tarsus or the pretarsal fascia, to reconstruct a stable double eyelid.It is a popular double eyelid plasty tal from December 2019 to February 2022.Aplio ultrasound 18 MHz probe (PHILIPS ELITE) was used to observe and evaluate the difference in tissue structure of pretarsal fat fascia and clinical effect.

2 | DATA AND ME THODS 2 . 1 |
General DataThe patients with congenital single eyelid underwent double eyelid blepharoplasty with the orbital septum method at the Plastic and cosmetic surgery department of Hunan provincial people's hospital and the same number of congenital double eyelid volunteers from December 2019 to February 2022.Preoperative eyelid ultrasound images as Group A, postoperative follow-up 6-12 months eyelid ultrasound images as Group B, and congenital double eyelid volunteers as Group C. Inclusion criteria: (1) patients aged >18 years; (2) Patients without history of ocular trauma, family history of ocular abnormality, previous ocular surgery, and other ocular diseases; (3) No histomorphological loss or space-occupying lesion of upper eyelid, and local deformity of upper eyelid; (4) Patients who have not received Botox-A injection within 1 year.Exclusion criteria: (1) Patients who cannot follow-up for more than 6 months after operation; (2) Patients who have received other cosmetic treatments such as upper eyelid injection after operation; (3) Patients who have other systemic or local diseases after operation, affecting the upper eyelid morphology.
Point a: the intersection of pupil midline and double eyelid line.(if single eyelid, Point a: on the midline of pupil is 7 mm from the eyelid margin); (Figure 1).Point b: The midpoint between point a on double eyelid line level and outer canthus.(if single eyelid, Point b: The midpoint between point a and the outer canthus is 7 mm away from the eyelid margin); (Figure 2).Point c: The midpoint between point a on double eyelid line level and inner canthus.(if single eyelid, Point c: The midpoint between point A and inner canthus is 5 mm away from the eyelid margin).

F I G U R E 1
Orbital septum double eyelid Blepharoplasty preoperative eyelid labeling ultrasound observation point a b c. (A) Eye opening, preoperative eyelid open eyes before observation; (B) Eye closure, preoperative eyelid labeing point a b c before observation.Point a: On the midline of pupil is 7 mm from the eyelid margin; Point b: The midpoint between point a and the outer canthus is 7 mm away from the eyelid margin; Point c: The midpoint between point A and inner canthus is 5 mm away from the eyelid margin.F I G U R E 2 Orbital septum double eyelid Blepharoplasty postoperative eyelid labeling ultrasound observation point a b c. (A) Eye opening, postoperative eyelid open eyes before observation; (B) Eye closure, postoperative eyelid labeing point a b c before observation.Point a: The intersection of pupil midline and double eyelid line; point b: The midpoint between point a on double eyelid line level and outer canthus; point c: The midpoint between point a on double eyelid line level and inner canthus.

F I G U R E 3
Congenital double eyelid labeling ultrasound observation point a b c. (A) Eye opening, congenital double eyelid open eyes before observation; (B) Eye closure, congenital double eyelid labeing point a b c before observation.Point a: The intersection of pupil midline and double eyelid line; point b: The midpoint between point a on double eyelid line level and outer canthus; point c: The midpoint between point a on double eyelid line level and inner canthus.
), the pretarsal fat fascia layer is divided into two layers: superficial loose fat fascia layer showing hypoechoic image and deep dense fascia layer showing hyperechoic image respectively.The dense fascia layer is close to the tarsus surface and very thin, but the difference is not significant between three groups.The difference of the thickness of loose fatty fascia tissue in group A, B, and C as followed: In Group A (98 eyes), The thickness of point a was 1.04 ± 0.23 mm; point b is 2.46 ± 0.51 mm; point c is 2.52 ± 0.44 mm.In Group B (98 eyes), The thickness of point a was 0.86 ± 0.20 mm; point b is 2.00 ± 0.31 mm; point c is 1.79 ± 0.24 mm.
came shallow and obvious bilaterally asymmetrical double-eyelid F I G U R E 4 Ultrasonic observation of pretarsal anatomical layer in group A, B, and C. (A) single eyelid ultrasound image before orbital septum double eyelid blepharoplasty preoperative group; (B) ultrasound image before orbital septum double eyelid blepharoplasty postoperative group; (C) congenital double eyelid group ultrasound image; (1) skin; (2) Orbicularis oculi muscle; (3) Loose pretarsal fat fascia layer; (4) tarsus; (5) Fusion part of levator palpebrae superioris aponeurosis and orbital septum; (6) Dense pretarsal fascia layer.TA B L E 1 Comparison of the thickness in point a, b, and c between double eyelid blepharoplasty using orbital septum before and after operation.
All the above indexes are normal distribution by normal distribution test.p-values <0.05 were considered statistically significant.Data were presented as mean ± standard deviation (M ± SD).
drive.The key to orbital septum double eyelid blepharoplasty lies in removing pretarsal loose fat fascia tissue, making orbital septum flap covering tarsus to forming a tight tissue structure in front of tarsus.The thick anterior tarsal fat fascia not only makes the double eyelid thick and fleshy but may also cause the loss of double eyelid looseness.The orbital septum is connected to levator palpebrae superioris aponeurosis, and the muscle and skin in front of tarsus are connected to the orbital septum inferior.This serves to reconstruct the physiological branches of the levator palpebrae superioris observed 98 congenital single eyelid double eyelid blepharoplasty with orbital septum before and after operation ultrasound imaging and 98 congenital double eyelid, Ultrasound showed that the three groups of pretarsal fat fascia were divided into two layers: low echo loose pretarsal fat fascia layer and high echo dense pretarsal fascia layer.In ultrasound imaging, the dense pretarsal fascia layer parallel extended forward and close to the surface of tarsus after the orbital septum and levator palpebrae superioris aponeurosis fusion.The loose pretarsal fat fascia layer was the continuation of fat behind orbicularis oculi muscle in front of tarsus.Ultrasound showed the thickness of dense pretarsal fascia layer was closely connected with tarsal surface and there was no significant difference between the three groups.Therefore, we only measured the thickness of loose pretarsal fat fascia layer, The thickness of pretarsal fat fascia layer was significant difference in Group A and B, Point a, b, and c in Group A thicker than that in Group B. According to some studies shown, the thickness of pretarsal muscle and skin between single eyelid and double eyelid was no significant difference, but we found the thickness of pretarsal fat fascia layer was quite different in our study, which suggested that we could reduce the thickness of tissue under the incision by removing the thicker pretarsal fat fascia layer, meanwhile avoid the adverse effect of removing more orbicularis oculi muscle.There was no significant difference in the thickness of pretarsal fat fascia between Group B and C, indicating that the structure of pretarsal fat fascia was similar to that of congenital double eyelid after orbital septum double eyelid blepharoplasty, suggesting that orbital septum double eyelid blepharoplasty could change the structure of pretarsal fat fascia and make it similar to congenital double eyelid, which is one of the anatomical bases for its good clinical effect.Double eyelid blepharoplasty with orbital septum method to remove the loose pretarsal fat fascia layer, keep the dense pretarsal fascia close to the tarsus and retain the orbicularis oculi muscle under the incision.It may reconstruct the physiological tight tissue in front of tarsus thus the double eyelids feel lightness.The orbital septum flap is turned down and then fixed with the orbicularis oculi and pretarsal fascia, which covers the anterior upper part of the tarsus, TA B L E 2 Comparison of the thickness in point a, b, and c between Orbital septum double eyelid Blepharoplasty postoperative eyelid and congenital double eyelid.All the above indexes are normal distribution by normal distribution test.p-values <0.05 were considered statistically significant.Data were presented as mean ± standard deviation (M ± SD).There was not significant differences between Group B and C. TA B L E 3 Comparison of the thickness in point a, b, and c between single eyelid and double eyelid.

F I G U R E 5
All the above indexes are normal distribution by normal distribution test.p-values <0.05 were considered statistically significant.Data were presented as mean ± standard deviation (M ± SD).There was significant differences between Group A and C. Typical cases.(A) Preoperative image.(B) Eye opening, 12 month postoperative image; (C) Eye closure, 12 month postoperative image.