Category of upper eyelid morphology and the preferred double eyelid shape in Asians according to questionnaire survey

The morphological classification of the upper eyelid in Asian people is complex and diverse and usually not consistent with what we know well.


| INTRODUC TI ON
Not only does appearance play a vital role in interpersonal interactions, 1 but it can also induce a feeling of well-being and improve self-esteem. 2In other words, appearances have a positive impact on overall health. 3The eyes are most easily noticed and can play a role in nonverbal communications.The concept of eye beauty among Asian people has changed to mirror that of Western culture.In addition, as people seriously consider their appearances, focus is required regarding the process of transforming single eyelids into double eyelids to meet the demands of beauty seekers.Beauty seekers are more interested in being unique according to their preferences.We should conduct in-depth research on eye aesthetics.Based on previous surveys, the double eyelid rate of Caucasians is 99% and that of Mongolians is only 50%.The eyelids of Asians are characterized by a single eyelid, an upward lateral canthal, and a pronounced epicanthic fold.However, only a few Asians have this feature. 4When the prevalence of the double eyelid in Chinese people living in Malaysia was calculated, it was found to be as high as 70.1%, 5 which is higher than we previously thought.Therefore, the objective of this study is to consummate the classification of upper eyelid morphology and determine the preferences for morphology to provide a reference for plastic surgeons.

| The questionnaire design
The study is a descriptive study.Questionnaires were adminis-

| Classification of upper eyelid morphology
The upper eyelid type was divided into 10 categories prior to the study, including single eyelid, parallel-shaped double eyelid, fanshaped double eyelid, parallel fan-shaped double eyelid, opened fan-shaped double eyelid, crescent-shaped double eyelid, hiddenshaped double eyelid, horizontal-shaped double eyelid, triangleshaped double eyelid, and multiple-fold eyelid (Figure 1).

| The questionnaire information
The information collected in the questionnaire was as follows: (1) social factors, including sex, age, native place, education background, occupation, income, and marital status; (2) classification of upper eyelid morphology, the preferred type, and information; (3) information about eye satisfaction and willingness to undergo blepharoplasty among the population who did not receive blepharoplasty; (4)   for the population willing to undergo blepharoplasty, the information of selected hospitals, preoperative considerations, postoperative concerns, and other factors; and (5) volunteered eye photographs (look straight ahead, 20-30 cm away from the lens).

| Statistical analysis
All statistical analyses were conducted using SPSS Statistics Software 26.0.Significance testing was a chi-square test, with a significance threshold of p < 0.05.

| Demographics
The subjects of this study consisted of a convenience sample of 640 individuals, and the descriptive information is shown in Table 1.
After removing the disqualified images, a total of 485 eyes of 247 people were reviewed.These photographs did not include those that underwent blepharoplasty.Three plastic surgeons were asked to judge the type of eyelid in the photographs.

| Natural upper lid morphology
For all the people who provided photographs and did not undergo blepharoplasty, we grouped their eyes and found that the number of people with a single eyelid was 121 (24.9%), and most of the double eyelid types were open fan-shaped double eyelids (21.0%), fanshaped double eyelids (16.3%), and hidden-shaped double eyelids (12.6%).The proportion of upper eyelid morphology differed significantly between males and females (p = 0.000).The eyelid type with the highest proportion in men was single eyelids (38.9%), whereas most of the women presented with open fan-shaped double eyelids (26.0%) (Figure 2).The prevalence of a double eyelid in the women (82.0%) was higher than that observed in the men (61.1%).

| The preferred double eyelid morphology
There were significant differences in the preferred double eyelid morphology between men and women (p = 0.010).The ideal dou-  common among men and women (Figure 3).However, the distinction among the different age groups (p = 0.060) and the native place (p = 0.316) was not significant.

| Willingness to undergo blepharoplasty
Of the questionnaires collected, 139 people were willing to undergo double blepharoplasty and 433 were not.For those who were willing to undergo blepharoplasty, there were significant differences in sex (p = 0.015), income (p = 0.048), and marital status (p = 0.019) (Table 2).Many factors need to be considered before and after surgery.Before surgery, people focused on the aesthetic of the doctors (29.2%), the cost of the operation (23.8%) and the service (16.2%) (Figure 4).In addition, people cared about the effects of the operation (28.4%), complications (25.3%), and scars (22.2%) (Figure 5).

| DISCUSS ION
The eyelid fold line classically is typically thought of as a crease located on the upper eyelid. 6There are many categories of eyelid creases.According to the height from the eyelid crease to the upper eyelid margin, the eyelid type was divided into single eyelid, low eyelid crease, and double eyelid. 7Based on the relative position be-  9 This study also pointed out that the ratio of single eyelids and eyelids that were hidden-shaped was significantly higher in males than in females.These findings show that the shape of the male eyelid is more implicit than that of the female eyelid.
Additionally, the study also found that the prevalence of double eyelids among Asian females was 82.0%, which is close to that reported in females by Chen in 2013. 16In general, the largest proportion of double eyelids are fan-shaped and opened fan-shaped.In addition, the authors found that some eyelid creases were shallow, while others were deeper.Cheng thought that some double eyelids are gradually formed during the process of growth, but because of the few fibrous connections, weak upper eyelid muscles, and the presence of fat at birth, double eyelid creases are not always formed.As age increases, the elasticity and tension of the eyelid skin becomes stronger, thus forming a double eyelid. 17The author suspects that a shallow double upper eyelid is because there are few distal fibers  | 3367 considered an important feature of beautiful and youthful eyes. 19me doctors transplant fat or inject filler to increase the upper eyelid volume, 20  Caucasians, and the height of the tarsus plays an important role in the formation of eyelid folds. 23However, many Asians overlook this anatomical difference.As time progressed and because Western movies were introduced in the 1980s, Asians increasingly pursued a depressed crease and a hollowing of the upper lid between the medial and central compartments, 24 which is achieved by removing additional fat from the upper eyelid during blepharoplasty.However, excessive removal of fat and skin results in an artificial eyelid condition. 25The previous discussion revealed that the purpose of blepharoplasty is to create a natural double eyelid that conforms to ethnic characteristics.Moreover, it is crucial to consider the patient's opinion to ensure their satisfaction.
Many studies have shown that aesthetic formation is a complex neuropsychological process whose mechanism is based on the functions of cognitive and affective brain systems. 26The perception of beauty varies from person to person and is closely related to cultural background, national characteristics, and living environment.Men and women perceive beauty differently, and the biggest difference between them is that men prefer open fan-shaped double eyelids while women choose crescent-shaped double eyelids.In addition, most people showed a preference for a parallel fan-shaped, a parallel-shaped or an open fan-shaped double eyelid, which is similar to other studies, which suggested that an infold double eyelid is the most popular. 27is curvature makes the eyes look brighter and more attractive. 28 this study, sex, income, and marital status had statistical significance in accepting blepharoplasty.Women are more willing to undergo blepharoplasty than men.This is consistent with previous research, which reports that women are more likely to undergo plastic surgery than men. 29Among Koreans, employment status is positively correlated with acceptance of plastic surgery, but student status has no correlation with acceptance of plastic surgery. 30In this study, the two groups with an income of less than 3000 yuan and 5000-10 000 yuan had the highest acceptance of double eyelid formability.The reason may be related to the fact that most of the respondents with an income of less than 3000 yuan are students.
They are more open-minded and have higher expectations in terms of appearance, are influenced by Western culture and have online beauty anxiety.Jung and Hwang showed similar results in that they showed that body appreciation had a negative influence on the acceptance of cosmetic surgery in Korean and American female university students. 31per eyelid blepharoplasty is also a procedure associated with a high level of patient satisfaction. 32

CO N FLI C T O F I NTER E S T S TATEM ENT
The authors declare that they have no conflicts of interest to disclose.

ACK N OWLED G M ENTS
None.

E TH I C S S TATEM ENT
This article does not contain any studies with human participants or animals performed by any of the authors.

I N FO R M ED CO N S ENT
All the participants agreed to the study.

R E FE R E N C E S
tered online and offline between December 2020 and December 2021.The main research population included individuals who were 15-64 years old.The following groups were excluded: (1) history of periocular surgery (excluding blepharoplasty); (2) eye diseases and systemic metabolic diseases (such as thyroid diseases, diabetes, and systemic lupus erythematosus); (3) patients with high myopia (myopia ≥600 degrees); and (4) long-term wearing of keratoscopes.

F I G U R E 1
Upper eyelid classification of upper eyelid morphology (the blue arrow indicates the start point of the eyelid line).(A) Parallelshaped double eyelid: the double eyelid line is parallel to the upper eyelid margin and is arc-shaped, with the same width inside and outside.(B) Fan-shaped double eyelid: the double eyelid line starts from the inner canthus and gradually widens outward along the upper eyelid margin.(C) Parallel fan-shaped double eyelid: the double eyelid line starts from the upper part of the inner canthus, runs outwardly parallel to the eyelid margin and is slightly wider laterally.(D) Opened fan-shaped double eyelid: the inner side of the double eyelid line is covered by the inner canthus; the double eyelid line starts from the inner 1/5 with the point of origin located medial to the medial edge of the cornea and gradually widens outside.(E) Crescent-shaped double eyelid: the double eyelid line is wide in the middle and slightly narrow inside and outside.(F) Hidden-shaped double eyelid: the double eyelid line appears when the eyes are open incompletely but disappears when the eyes are open completely; the double eyelid line starts lateral to the lateral edge of the cornea.(G) Horizontal-shaped double eyelid: the double eyelid line is horizontal, and the medial and lateral sides are wide.(H) Triangle-shaped double eyelid: the double eyelid line is triangular, wide inside and narrow outside.It is common in older people.(I) Multiple-fold eyelid: there are multiple eyelid lines.(J) Single eyelid: there is no eyelid line on the upper eyelid.
Most of the photograph providers (83.7%) were young people aged 15-34 years.In this part of the population, the main eyelid type is still a single eyelid and an open fan-shaped double eyelid.Among them, open fan-shaped double eyelids (n = 59, 27.7%) accounted for the largest proportion of people aged 15-24 years, while single eyelids (n = 53, 27.9%) accounted for the largest proportion of people aged 25-34 years.Generally, the eyelid types with the highest proportions were single eyelid (26.1%), open fan-shaped double eyelid (23.4%), and fan-shaped double eyelid (16.0%).
ble eyelid shapes were open fan-shaped (19.3%), parallel fan-shaped (18.0%), and parallel-shaped (15.8%) in men, while crescent-shaped TA B L E 1 Data of the information of individuals.

F I G U R E 3
tween the double eyelid crease and the epicanthal fold, Paki et al. divided eyelid shape into three categories: infold, onfold, and outfold 8 ; Based on the position of the eyelid crease to the epicanthic folds, the eyelid type was as follows: (A) Single eyelid (no visible lid crease), (B) Low eyelid crease (low-seated, nasally tapered, including hidden fold), (C) Double eyelid crease, infold type: the height of the upper lid crease is lower than the epicanthal fold, (D) Double eyelid crease, onfold type: the height of the crease is on the epicanthal fold, (E) Double eyelid crease, outfold type: the height of the crease is higher than the epicanthal fold (asterisk), and (F) Double eyelid crease, outfold type without an epicanthal fold. 9Through observation and analysis, we found that there are three kinds of natural upper eyelid morphology: single eyelid, double eyelid, and multiple-fold eyelid.Double eyelids could be subdivided into parallel-shaped double F I G U R E 2 The upper eyelid shapes among males and females.Investigation of the preferred double eyelid morphology.eyelids, fan-shaped double eyelids, parallel fan-shaped double eyelids, opened fan-shaped double eyelids, crescent-shaped double eyelids, hidden-shaped double eyelids, horizontal-shaped double eyelids, and triangle-shaped double eyelids.This is more detailed than the traditional double eyelid classification, which basically covers all the double eyelid morphology, standardizing the terms of double eyelid morphology and explaining all kinds of double eyelid morphology.It also indicates that some double eyelid types appear in different age groups.In 2021, Wang divided double eyelids into five types according to eyelid shape: slightly fan-shaped, obviously fan-shaped, crescent-shaped, low parallel, and high parallel. 10This study is similar to Wang's study in that both studies exclude threedimensional interference factors and focus on the relative positional relationship between the crease line and the eyelid margin line in a two-dimensional space, excluding the effects of skin quality, eyebrow shape and position, condition of the eyelashes (color, length, and shape), eye shape, eye axis, vertical distance of palpebral fissure, and the proportion of the pretarsal space to the upper lid fold on eye aesthetics. 11-15This paper solely focuses on the attractiveness of the upper eyelid shape and refines the classification of double eyelids to help plastic surgeons better satisfy the demand of beauty seekers.The shape of a person's eyelids is not symmetrical.To improve the accuracy of the study, we analyzed each eye individually and classified by three plastic surgeons.Research has shown that male Asians have lower folds of the upper eyelid than female Asians (4-6 mm, 6-8 mm).

TA B L E 2 F I G U R E 4 F I G U R E 5
Data of the individuals who are willing to undergo blepharoplasty.Preoperative considerations.Postoperative considerations.
while studies have shown that there are fluffy fibers in the anterior orbital septum, which prevents the release of fat.When the fibers are cut surgically, the orbital fat is released, thus revealing excess fat and confirming that an upper eyelid is not caused by a lack of fat. 21It is worth noting that Asians and Caucasians have different appearances, despite both groups having double eyelids.Compared to Caucasians, Asians have few fibers in the distal aponeurosis of the upper eyelid, low fusion points of the orbital septum and levator aponeurosis, more fat in the orbital septum, a thicker orbicularis oculi muscle, and thicker upper eyelid skin. 22Some scholars have found that Asians generally have a narrower tarsus than

5 |
Plastic surgeons should focus on the patients' perceptions before and after surgery.Before surgery, patients focus on the doctor's capacity to create positive aesthetic effects and the cost of surgery.After surgery, patients are more concerned about complications, side effects, and scars.Most patients expect a high success rate, but any surgery is risky.Higher expectations for beauty are driving more people to opt for blepharoplasty in the hope of a more attractive appearance.To avoid disputes with patients, the most important thing is to understand the patients' preferences prior to the surgery and to carefully inform the patients of the risks of surgery.The current research is not without limitations.Regarding the questionnaire survey, we collected a few valid photographs, and most of them were provided by young people aged 15-34.There is a lack of information about elderly individuals.Information about the elderly needs further investigation.In addition, this study mainly focused on preoperative research without investigating postoperative information.In a future study, we will improve the postoperative data to better understand the needs of beauty seekers.CON CLUS IONS In this study, we know that the most popular upper eyelid shapes were single eyelids, open fan-shaped double eyelids, and fan-shaped double eyelids.The parallel fan-shaped, parallel-shaped, and open fan-shaped of the double eyelid are favored by men and women.The significance of this study lies in reclassifying the morphology of natural double eyelids and standardizing the terminology.The shape of the double eyelid favored by Oriental was clarified.This is of guiding significance to the design of double eyelid surgery, the most common blepharoplasty in the East.AUTH O R CO NTR I B UTI O N Sinan Zhao and Xin Yan designed the research study.Sinan Zhao, Dongfeng Zheng, Shuqin Wang, and Xin Yan collected the data.Sinan Zhao and Huaqiang Ge analyzed the data.Sinan Zhao and Dongfeng Zheng wrote the paper.Qian Tan revised the article and monitored the data integrity.All authors have read and approved the final manuscript.