- Email: [email protected]
Asymmetry of the palpebral fissure and upper eyelid crease in Koreans
Journal of Plastic, Reconstructive & Aesthetic Surgery (2007) 60, 251e255
Asymmetry of the palpebral fissure and upper eyelid crease in Koreans W.C. Song a, S.J. Kim b, S.H. Kim c, K.S. Hu d, H.J. Kim d, K.S. Koh a,* a
Department of Anatomy, College of Medicine, Konkuk University, 322 Danwol-dong, Chungju, Chungbuk 380-701, Republic of Korea b Department of Plastic and Reconstructive Surgery, National Medical Center, 243 Euljiro 6 (yuk)-ga, Jung-gu, Seoul 100-799, Republic of Korea c Department of Plastic and Reconstructive Surgery, College of Medicine, Konkuk University, 322 Danwol-dong, Chungju, Chungbuk 380-701, Republic of Korea d Division in Anatomy and Developmental Biology, Department of Oral Biology, College of Dentistry, Oral Science Research Center, Human Identification Research Center, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-752, Republic of Korea Received 25 January 2006; accepted 23 April 2006
KEYWORDS Asymmetry; Palpebral fissure; Upper eyelid crease; Inclination; Height; Width
Summary The purpose of the present study was to quantify the asymmetry of the palpebral fissure (PF) and upper eyelid crease in normal Koreans. Photographs were taken of 273 males and 321 females aged from 20 to 49 years with a standard head position and eyes open. We investigated the presence of asymmetries of the PF inclination (PFI), PF height (PFH), PF width (PFW) and the upper eyelid crease. The criteria for asymmetry were 2 for PFI, 1 mm for PFH and 3 mm for PFW. The PFH was larger on the right side than on the left side, whereas the PFW was larger on the left than on the right. The prevalence of asymmetry of the PFI, PFH and PFW was 22.3%, 24.2% and 18.3% in males, and 35.8%, 26.5% and 18.7% in females, respectively. In most cases of PF asymmetry, the PFH was larger on the right and the PFW was larger on the left. A left-only upper eyelid crease was more common than a right-only upper eyelid crease in both sexes. The asymmetry of the PF was generally more common in females. ª 2006 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.
* Corresponding author. Tel.: þ82 43 840 3733; fax: þ82 43 851 9329. E-mail address: [email protected] (K.S. Koh).
1748-6815/$-seefrontmatterª2006BritishAssociationofPlastic,ReconstructiveandAestheticSurgeons.PublishedbyElsevierLtd.All rightsreserved. doi:10.1016/j.bjps.2006.04.027
252
W.C. Song et al.
Differences between the right and left sides of the head and face are always present, but are only regarded as asymmetries when certain thresholds are exceeded. Many studies have applied various criteria to estimating the prevalence of asymmetry, and most have found right-dominant asymmetries of the head and face to be present.1e7 Although the individual structures of the face including the eyes, nose and mouth may be asymmetric, only a few studies have considered asymmetries of the palpebral fissure (PF).5,8,9 Moreover, some of the applied criteria have been inappropriate or difficult to assess. In addition to PF size, there have been many investigations of the prevalence and classification of the upper eyelid crease; these studies have been mainly in Asians10 because most Caucasians have an upper eyelid crease.11 However, asymmetry of the upper eyelid crease is not well described.8 The purposes of the present study were to quantify the asymmetries of the PF and upper eyelid crease in Korean subjects, and to suggest appropriate criteria for these asymmetries.
Materials and methods Five hundred and ninety-four Korean volunteers (273 males and 321 females) were recruited, none of whom had obvious deformity or injury of the eyelid or surgical history. The age of the subjects ranged between 20 and 49 years, with a mean of 33.1 years. We used standardized photographs to investigate the PF size and the presence of an upper eyelid crease. The PF is a relatively small structure and many subjects blink or frown when a measuring instrument is placed close to the eyes, and hence direct measurements were considered less accurate than indirect measurements using photographs. Each subject was photographed from a distance of 1.5 m (F-801s, Nikon, Japan) whilst seated with a standard head position and eyes open, with a scale bar included in the image. The
Table 1 Sex Male Female Total
Figure 1 Metric measurement items. 1: Palpebral fissure height; 2: palpebral fissure width; and 3: palpebral fissure inclination.
photographs were printed at a size of 8 10 inches, scanned at 150 dpi (Epson Perfection 1640SU, Epson, Japan), with subsequent measurements made using an image analyser (Image-Pro Plus 5.0, MediaCybernetics, Silver Spring, MD, USA). The PF inclination (PFI), PF height (PFH) and PF width (PFW) were measured to investigate the degree of asymmetry (Fig. 1). The effects of the epicanthus and/or epiblepharon that are prevalent in Asians were not considered in the present study, because the focus was on the natural PF shape. Various asymmetry criteria have been applied in previous studies; we applied new criteria for the presence of a difference between the right and left sides that were based on the mean values as measured in the present study. We also investigated asymmetry in the presence of an upper eyelid crease. The calculations and statistical analyses were performed using standard computer software (SPSS for Windows v12.0, SPSS Inc., Chicago, IL, USA).
Results The values of all measured parameters are listed in Table 1. Positive values of the PFI indicate that the lateral canthus was higher than the medial canthus. The PFI was larger in females than in males, but the difference was not statistically significant (independent-samples t-test, p > 0.05). The PFI also did not differ significantly between the two sides (paired-samples t-test, p > 0.05). However, both the PFH and PFW differed significantly with sex (p < 0.01) and side (p < 0.05): the PFH was
Values of the measurements Height*,** (mm)
Inclination ( )
Width*,** (mm)
Right
Left
Right
Left
Right
Left
8.5 2.5 9.2 2.5 8.9 2.5
8.4 2.4 9.3 2.5 8.9 2.5
10.0 1.6 10.2 1.6 10.1 1.6
9.9 1.6 10.0 1.7 9.9 1.6
28.2 3.1 26.8 3.6 27.5 3.5
29.0 3.0 27.6 3.5 28.2 3.4
Mean S.D. *There was a statistically significant difference between both sexes (p < 0.05); **There was a statistically significant difference between both sides (p < 0.05).
Palpebral fissure asymmetry Table 2
253
Prevalence of the asymmetry of the palpebral fissure inclination
Sex
Right-sidedominant (%)
Symmetric (%)
Left-sidedominant (%)
Asymmetric (%) (right þ left)
Male* Female* Total
11.3 17.1 14.5
77.7 64.2 70.4
11.0 18.7 15.1
22.3 35.8 29.7
*There were statistically significant differences between both sexes (p < 0.05); right-side-dominant: right-minus-left difference more than 2 ; symmetric: right-minus-left or left-minus-right difference less than 2 ; and left-side-dominant: left-minus-right difference more than 2 .
larger on the right than on the left, the PFW was larger on the left than on the right, females had a larger PFH, and males had a larger PFW. We applied the following new criteria for the presence of asymmetry: 2 for PFI, 1 mm for PFH and 3 mm for PFW; the terminology ‘right-sidedominant’ (or ‘left-side-dominant’) asymmetry indicates that right-minus-left (or left-minus-right) difference was higher than the above criteria in individual measurements. In case of the PFI, right-side-dominant asymmetry (14.5%) and leftside-dominant asymmetry (15.1%) showed similar prevalences (Table 2), with PFI asymmetry being more common in females (35.8%) than in males (22.3%). In the case of PFH, right-side-dominant asymmetry (16.7%) was about twice as common as left-side-dominant asymmetry (8.7%), as was independent of sex (Table 3). The overall prevalence of PFH asymmetry was similar in both sexes: 24.2% in males and 26.5% in females. In the case of PFW, left-side-dominant asymmetry (14.5%) was over three times more common than right-side-dominant asymmetry (4.0%), in contrast to asymmetry of the PFH (Table 4). The overall prevalence of PFW asymmetry was similar in both sexes: 18.3% in males and 18.7% in females. An upper eyelid crease was more common in females. The prevalence of an upper eyelid crease being absent in both eyes was similar to the prevalence of both-present cases in females. However, both-absent cases were much more
Table 3
common than both-present cases in males (Table 5). A left-only upper eyelid crease (7.4%) was over twice as common as a right-only upper eyelid crease (3.5%). The overall prevalence of an upper eyelid crease being present in only one eye was 10.3% in males and 11.5% in females.
Discussion Farkas5 reported that the prevalences of PFH and PFW asymmetry were below 2%, and that the prevalence of PFI asymmetry was 2.3% in both sexes in Caucasians. However, inexact criteria for the difference between the sides were applied in his study. Lam et al.9 reported that applying a criterion of 1 mm resulted in a prevalence of PFH asymmetry of 5.7% in Caucasians. Previous studies have found that the PFH is larger in Caucasians than in Asians,10,12 and it is reasonable to assume that the asymmetry of the PFH would be larger in people having a large PF (if the asymmetry is based on an absolute rather than a percentage measurement). However, although we applied the same criterion as Lam et al.,9 the prevalence of PFH asymmetry in the present study was much higher. In addition, when we applied more strict criteria to asymmetries of the PFI and PFW, the prevalences were also much higher than those of Farkas.5 Few studies have investigated PF asymmetry in different races, which makes it
Prevalence of the asymmetry of the palpebral fissure height
Sex
Right-sidedominant (%)
Symmetric (%)
Left-sidedominant* (%)
Asymmetric (%) (right þ left)
Male Female Total
15.8 17.5 16.7
75.8 73.5 74.6
8.4 9.0 8.7
24.2 26.5 25.4
*There was statistically significant difference between both sides (p < 0.05); right-side-dominant: right-minus-left difference more than 1 mm; symmetric: right-minus-left or left-minus-right difference less than 1 mm; and left-side-dominant: leftminus-right difference more than 1 mm.
254 Table 4
W.C. Song et al. Prevalence of the asymmetry of the palpebral fissure width
Sex
Right-sidedominant (%)
Symmetric (%)
Left-sidedominant (%)
Asymmetric (%) (right þ left)
Male Female Total
3.3 4.7 4.0
81.7 81.3 81.5
15.0 14.0 14.5
18.3 18.7 18.5
Right-side-dominant: right-minus-left difference more than 3 mm; symmetric: right-minus-left or left-minus-right difference less than 3 mm; and left-side-dominant: left-minus-right difference more than 3 mm.
difficult to compare the results obtained. However, it is considered that the prevalence of PF asymmetry is particularly high in northeast Asians (including Koreans), and more studies on PF asymmetry are needed on Japanese and Chinese populations. In the present study, there was no tendency for side dominance in the PFI, whereas the PFH and PFW exhibited right- and left-side-dominant tendencies, respectively, in both the mean value and the prevalence of the asymmetry. We previously reported that the calvarium and facial skeleton are vertically larger on the right than on the left in Koreans.7 Woo1 reported that the zygoma and maxilla were larger on the left than on the right. These observations are consistent with those in the present study showing that the PFH was larger on the right and the PFW was larger on the left. Because a right-side-dominant tendency of the head and face is evident in other races (including northeast Asians),1e7 it will be interesting to examine the side dominance of PF asymmetry in other races. Ishikawa8 reported that the prevalence of asymmetry in the presence of an upper eyelid crease in Japanese adults was 5.7% (3.8% in males and 6.7% in females; recalculated from his tables). Although the presence of a right- or left-only upper eyelid crease in adults was not reported, Ishikawa8 demonstrated that left-only upper eyelid creases were about four times more common than right-only upper eyelid creases in infants between 6 months and 1 year old. Therefore, these
Table 5
tendencies for asymmetry of the upper eyelid crease, including side (left-only > right-only) and sex (females > males) differences, are considered as being common in northeast Asians, but further comparative studies are needed to investigate whether these asymmetry traits are present in Caucasians or other races. PF asymmetry was more frequent in females in the present study, especially in the case of the PFI. Ishigawa8 reported that asymmetry of the upper eyelid crease was more common in females. However, the presence of few gender differences in the PF and facial asymmetries in Caucasians has also been reported.4,5 We therefore also consider the gender differences in the PF to be a trait of northeast Asians. The prevalence of asymmetries varies with the criteria used to measure them. Although various criteria for PF asymmetry have been reported,5e8 we consider them all to be inappropriate for defining the asymmetry. We suggest that the most appropriate criteria for assessing PFI, PFH and PHW asymmetry are 2 , 1 mm and 3 mm, respectively; these criteria correspond to the mean values found in the present study. In conclusion, 20e25% of the Korean subjects in the present study had a PFH that was larger on the right side and a PFW that was larger on the left side, and this asymmetry was more common in females. Moreover, the prevalence of PF asymmetry was higher than that reported in Caucasians. Future studies should determine the degrees of asymmetry that require surgical correction.
Prevalence of asymmetry of the upper eyelid crease
Sex
Both absent (%)
Both present (%)
Right only (%)
Left only (%)
Asymmetric (%) (right þ left)
Male Female Total
65.6 43.0 53.4
24.1 45.5 35.7
2.2 4.7 3.5
8.1 6.8 7.4
10.3 11.5 10.9
Palpebral fissure asymmetry
References 1. Woo TL. On the asymmetry of the human skull. Biometrika 1931;22:324e41. 2. Figalova ´ P. Asymmetry of the face. Anthropologie 1969;7: 31e4. 3. Shah SM, Joshi MR. An assessment of asymmetry in the normal craniofacial complex. Angle Orthod 1978;48:141e8. 4. Farkas LG, Cheung G. Facial asymmetry in healthy North American Caucasians. An anthropometrical study. Angle Orthod 1981;51:70e7. 5. Farkas LG. Anthropometry of the head and face. 2nd ed. New York: Raven Press; 1994. p. 103e11. 6. Ferrario VF, Sforza C, Poggio CE, et al. Distance from symmetry: a three-dimensional evaluation of facial asymmetry. J Oral Maxillofac Surg 1994;52:1126e32.
255 7. Kim YS, Chung MS, Park DK, et al. Asymmetric study on the Korean skull using bilateral measurements. Korean J Phys Anthropol 2000;13:271e9. 8. Ishikawa T. Frequency and morphological change of double eyelid fold in relation to age. Hokkaido Igaku Zasshi 1995; 70:195e208. 9. Lam BL, Lam S, Walls RC. Prevalence of palpebral fissure asymmetry in white persons. Am J Ophthalmol 1995;120: 518e22. 10. Song WC, Park SH, Koh KS. Metric and non-metric characteristics of Korean eyes using standardized photographs. Korean J Phys Anthropol 2002;15:95e107. 11. Zamora RL, Becker WL, Cruster PL. Normal eyelid crease position in children. Ophthalmic Surg 1994;25:42e7. 12. Matsunaga RS. Westernization of the Asian eyelid. Arch Otolaryngol 1985;111:149e53.
Asymmetry of the palpebral fissure and upper eyelid crease in Koreans W.C. Song a, S.J. Kim b, S.H. Kim c, K.S. Hu d, H.J. Kim d, K.S. Koh a,* a
Department of Anatomy, College of Medicine, Konkuk University, 322 Danwol-dong, Chungju, Chungbuk 380-701, Republic of Korea b Department of Plastic and Reconstructive Surgery, National Medical Center, 243 Euljiro 6 (yuk)-ga, Jung-gu, Seoul 100-799, Republic of Korea c Department of Plastic and Reconstructive Surgery, College of Medicine, Konkuk University, 322 Danwol-dong, Chungju, Chungbuk 380-701, Republic of Korea d Division in Anatomy and Developmental Biology, Department of Oral Biology, College of Dentistry, Oral Science Research Center, Human Identification Research Center, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-752, Republic of Korea Received 25 January 2006; accepted 23 April 2006
KEYWORDS Asymmetry; Palpebral fissure; Upper eyelid crease; Inclination; Height; Width
Summary The purpose of the present study was to quantify the asymmetry of the palpebral fissure (PF) and upper eyelid crease in normal Koreans. Photographs were taken of 273 males and 321 females aged from 20 to 49 years with a standard head position and eyes open. We investigated the presence of asymmetries of the PF inclination (PFI), PF height (PFH), PF width (PFW) and the upper eyelid crease. The criteria for asymmetry were 2 for PFI, 1 mm for PFH and 3 mm for PFW. The PFH was larger on the right side than on the left side, whereas the PFW was larger on the left than on the right. The prevalence of asymmetry of the PFI, PFH and PFW was 22.3%, 24.2% and 18.3% in males, and 35.8%, 26.5% and 18.7% in females, respectively. In most cases of PF asymmetry, the PFH was larger on the right and the PFW was larger on the left. A left-only upper eyelid crease was more common than a right-only upper eyelid crease in both sexes. The asymmetry of the PF was generally more common in females. ª 2006 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.
* Corresponding author. Tel.: þ82 43 840 3733; fax: þ82 43 851 9329. E-mail address: [email protected] (K.S. Koh).
1748-6815/$-seefrontmatterª2006BritishAssociationofPlastic,ReconstructiveandAestheticSurgeons.PublishedbyElsevierLtd.All rightsreserved. doi:10.1016/j.bjps.2006.04.027
252
W.C. Song et al.
Differences between the right and left sides of the head and face are always present, but are only regarded as asymmetries when certain thresholds are exceeded. Many studies have applied various criteria to estimating the prevalence of asymmetry, and most have found right-dominant asymmetries of the head and face to be present.1e7 Although the individual structures of the face including the eyes, nose and mouth may be asymmetric, only a few studies have considered asymmetries of the palpebral fissure (PF).5,8,9 Moreover, some of the applied criteria have been inappropriate or difficult to assess. In addition to PF size, there have been many investigations of the prevalence and classification of the upper eyelid crease; these studies have been mainly in Asians10 because most Caucasians have an upper eyelid crease.11 However, asymmetry of the upper eyelid crease is not well described.8 The purposes of the present study were to quantify the asymmetries of the PF and upper eyelid crease in Korean subjects, and to suggest appropriate criteria for these asymmetries.
Materials and methods Five hundred and ninety-four Korean volunteers (273 males and 321 females) were recruited, none of whom had obvious deformity or injury of the eyelid or surgical history. The age of the subjects ranged between 20 and 49 years, with a mean of 33.1 years. We used standardized photographs to investigate the PF size and the presence of an upper eyelid crease. The PF is a relatively small structure and many subjects blink or frown when a measuring instrument is placed close to the eyes, and hence direct measurements were considered less accurate than indirect measurements using photographs. Each subject was photographed from a distance of 1.5 m (F-801s, Nikon, Japan) whilst seated with a standard head position and eyes open, with a scale bar included in the image. The
Table 1 Sex Male Female Total
Figure 1 Metric measurement items. 1: Palpebral fissure height; 2: palpebral fissure width; and 3: palpebral fissure inclination.
photographs were printed at a size of 8 10 inches, scanned at 150 dpi (Epson Perfection 1640SU, Epson, Japan), with subsequent measurements made using an image analyser (Image-Pro Plus 5.0, MediaCybernetics, Silver Spring, MD, USA). The PF inclination (PFI), PF height (PFH) and PF width (PFW) were measured to investigate the degree of asymmetry (Fig. 1). The effects of the epicanthus and/or epiblepharon that are prevalent in Asians were not considered in the present study, because the focus was on the natural PF shape. Various asymmetry criteria have been applied in previous studies; we applied new criteria for the presence of a difference between the right and left sides that were based on the mean values as measured in the present study. We also investigated asymmetry in the presence of an upper eyelid crease. The calculations and statistical analyses were performed using standard computer software (SPSS for Windows v12.0, SPSS Inc., Chicago, IL, USA).
Results The values of all measured parameters are listed in Table 1. Positive values of the PFI indicate that the lateral canthus was higher than the medial canthus. The PFI was larger in females than in males, but the difference was not statistically significant (independent-samples t-test, p > 0.05). The PFI also did not differ significantly between the two sides (paired-samples t-test, p > 0.05). However, both the PFH and PFW differed significantly with sex (p < 0.01) and side (p < 0.05): the PFH was
Values of the measurements Height*,** (mm)
Inclination ( )
Width*,** (mm)
Right
Left
Right
Left
Right
Left
8.5 2.5 9.2 2.5 8.9 2.5
8.4 2.4 9.3 2.5 8.9 2.5
10.0 1.6 10.2 1.6 10.1 1.6
9.9 1.6 10.0 1.7 9.9 1.6
28.2 3.1 26.8 3.6 27.5 3.5
29.0 3.0 27.6 3.5 28.2 3.4
Mean S.D. *There was a statistically significant difference between both sexes (p < 0.05); **There was a statistically significant difference between both sides (p < 0.05).
Palpebral fissure asymmetry Table 2
253
Prevalence of the asymmetry of the palpebral fissure inclination
Sex
Right-sidedominant (%)
Symmetric (%)
Left-sidedominant (%)
Asymmetric (%) (right þ left)
Male* Female* Total
11.3 17.1 14.5
77.7 64.2 70.4
11.0 18.7 15.1
22.3 35.8 29.7
*There were statistically significant differences between both sexes (p < 0.05); right-side-dominant: right-minus-left difference more than 2 ; symmetric: right-minus-left or left-minus-right difference less than 2 ; and left-side-dominant: left-minus-right difference more than 2 .
larger on the right than on the left, the PFW was larger on the left than on the right, females had a larger PFH, and males had a larger PFW. We applied the following new criteria for the presence of asymmetry: 2 for PFI, 1 mm for PFH and 3 mm for PFW; the terminology ‘right-sidedominant’ (or ‘left-side-dominant’) asymmetry indicates that right-minus-left (or left-minus-right) difference was higher than the above criteria in individual measurements. In case of the PFI, right-side-dominant asymmetry (14.5%) and leftside-dominant asymmetry (15.1%) showed similar prevalences (Table 2), with PFI asymmetry being more common in females (35.8%) than in males (22.3%). In the case of PFH, right-side-dominant asymmetry (16.7%) was about twice as common as left-side-dominant asymmetry (8.7%), as was independent of sex (Table 3). The overall prevalence of PFH asymmetry was similar in both sexes: 24.2% in males and 26.5% in females. In the case of PFW, left-side-dominant asymmetry (14.5%) was over three times more common than right-side-dominant asymmetry (4.0%), in contrast to asymmetry of the PFH (Table 4). The overall prevalence of PFW asymmetry was similar in both sexes: 18.3% in males and 18.7% in females. An upper eyelid crease was more common in females. The prevalence of an upper eyelid crease being absent in both eyes was similar to the prevalence of both-present cases in females. However, both-absent cases were much more
Table 3
common than both-present cases in males (Table 5). A left-only upper eyelid crease (7.4%) was over twice as common as a right-only upper eyelid crease (3.5%). The overall prevalence of an upper eyelid crease being present in only one eye was 10.3% in males and 11.5% in females.
Discussion Farkas5 reported that the prevalences of PFH and PFW asymmetry were below 2%, and that the prevalence of PFI asymmetry was 2.3% in both sexes in Caucasians. However, inexact criteria for the difference between the sides were applied in his study. Lam et al.9 reported that applying a criterion of 1 mm resulted in a prevalence of PFH asymmetry of 5.7% in Caucasians. Previous studies have found that the PFH is larger in Caucasians than in Asians,10,12 and it is reasonable to assume that the asymmetry of the PFH would be larger in people having a large PF (if the asymmetry is based on an absolute rather than a percentage measurement). However, although we applied the same criterion as Lam et al.,9 the prevalence of PFH asymmetry in the present study was much higher. In addition, when we applied more strict criteria to asymmetries of the PFI and PFW, the prevalences were also much higher than those of Farkas.5 Few studies have investigated PF asymmetry in different races, which makes it
Prevalence of the asymmetry of the palpebral fissure height
Sex
Right-sidedominant (%)
Symmetric (%)
Left-sidedominant* (%)
Asymmetric (%) (right þ left)
Male Female Total
15.8 17.5 16.7
75.8 73.5 74.6
8.4 9.0 8.7
24.2 26.5 25.4
*There was statistically significant difference between both sides (p < 0.05); right-side-dominant: right-minus-left difference more than 1 mm; symmetric: right-minus-left or left-minus-right difference less than 1 mm; and left-side-dominant: leftminus-right difference more than 1 mm.
254 Table 4
W.C. Song et al. Prevalence of the asymmetry of the palpebral fissure width
Sex
Right-sidedominant (%)
Symmetric (%)
Left-sidedominant (%)
Asymmetric (%) (right þ left)
Male Female Total
3.3 4.7 4.0
81.7 81.3 81.5
15.0 14.0 14.5
18.3 18.7 18.5
Right-side-dominant: right-minus-left difference more than 3 mm; symmetric: right-minus-left or left-minus-right difference less than 3 mm; and left-side-dominant: left-minus-right difference more than 3 mm.
difficult to compare the results obtained. However, it is considered that the prevalence of PF asymmetry is particularly high in northeast Asians (including Koreans), and more studies on PF asymmetry are needed on Japanese and Chinese populations. In the present study, there was no tendency for side dominance in the PFI, whereas the PFH and PFW exhibited right- and left-side-dominant tendencies, respectively, in both the mean value and the prevalence of the asymmetry. We previously reported that the calvarium and facial skeleton are vertically larger on the right than on the left in Koreans.7 Woo1 reported that the zygoma and maxilla were larger on the left than on the right. These observations are consistent with those in the present study showing that the PFH was larger on the right and the PFW was larger on the left. Because a right-side-dominant tendency of the head and face is evident in other races (including northeast Asians),1e7 it will be interesting to examine the side dominance of PF asymmetry in other races. Ishikawa8 reported that the prevalence of asymmetry in the presence of an upper eyelid crease in Japanese adults was 5.7% (3.8% in males and 6.7% in females; recalculated from his tables). Although the presence of a right- or left-only upper eyelid crease in adults was not reported, Ishikawa8 demonstrated that left-only upper eyelid creases were about four times more common than right-only upper eyelid creases in infants between 6 months and 1 year old. Therefore, these
Table 5
tendencies for asymmetry of the upper eyelid crease, including side (left-only > right-only) and sex (females > males) differences, are considered as being common in northeast Asians, but further comparative studies are needed to investigate whether these asymmetry traits are present in Caucasians or other races. PF asymmetry was more frequent in females in the present study, especially in the case of the PFI. Ishigawa8 reported that asymmetry of the upper eyelid crease was more common in females. However, the presence of few gender differences in the PF and facial asymmetries in Caucasians has also been reported.4,5 We therefore also consider the gender differences in the PF to be a trait of northeast Asians. The prevalence of asymmetries varies with the criteria used to measure them. Although various criteria for PF asymmetry have been reported,5e8 we consider them all to be inappropriate for defining the asymmetry. We suggest that the most appropriate criteria for assessing PFI, PFH and PHW asymmetry are 2 , 1 mm and 3 mm, respectively; these criteria correspond to the mean values found in the present study. In conclusion, 20e25% of the Korean subjects in the present study had a PFH that was larger on the right side and a PFW that was larger on the left side, and this asymmetry was more common in females. Moreover, the prevalence of PF asymmetry was higher than that reported in Caucasians. Future studies should determine the degrees of asymmetry that require surgical correction.
Prevalence of asymmetry of the upper eyelid crease
Sex
Both absent (%)
Both present (%)
Right only (%)
Left only (%)
Asymmetric (%) (right þ left)
Male Female Total
65.6 43.0 53.4
24.1 45.5 35.7
2.2 4.7 3.5
8.1 6.8 7.4
10.3 11.5 10.9
Palpebral fissure asymmetry
References 1. Woo TL. On the asymmetry of the human skull. Biometrika 1931;22:324e41. 2. Figalova ´ P. Asymmetry of the face. Anthropologie 1969;7: 31e4. 3. Shah SM, Joshi MR. An assessment of asymmetry in the normal craniofacial complex. Angle Orthod 1978;48:141e8. 4. Farkas LG, Cheung G. Facial asymmetry in healthy North American Caucasians. An anthropometrical study. Angle Orthod 1981;51:70e7. 5. Farkas LG. Anthropometry of the head and face. 2nd ed. New York: Raven Press; 1994. p. 103e11. 6. Ferrario VF, Sforza C, Poggio CE, et al. Distance from symmetry: a three-dimensional evaluation of facial asymmetry. J Oral Maxillofac Surg 1994;52:1126e32.
255 7. Kim YS, Chung MS, Park DK, et al. Asymmetric study on the Korean skull using bilateral measurements. Korean J Phys Anthropol 2000;13:271e9. 8. Ishikawa T. Frequency and morphological change of double eyelid fold in relation to age. Hokkaido Igaku Zasshi 1995; 70:195e208. 9. Lam BL, Lam S, Walls RC. Prevalence of palpebral fissure asymmetry in white persons. Am J Ophthalmol 1995;120: 518e22. 10. Song WC, Park SH, Koh KS. Metric and non-metric characteristics of Korean eyes using standardized photographs. Korean J Phys Anthropol 2002;15:95e107. 11. Zamora RL, Becker WL, Cruster PL. Normal eyelid crease position in children. Ophthalmic Surg 1994;25:42e7. 12. Matsunaga RS. Westernization of the Asian eyelid. Arch Otolaryngol 1985;111:149e53.