Anthropometry of eyelid and orbit in four southern Thailand ethnic groups.

OBJECTIVE To study the basic eyelid and orbital measurement in the four main ethnic groups of southern Thailand. MATERIAL AND METHOD The basic eyelid and orbital surface anatomy of 101 normal subjects aged 20-40 years old were measured in the four ethnic groups of which the majority of people in southern Thailand belong to: Thai, Chinese, Thai-Malay, and Thai-Chinese. RESULTS Of the 101 subjects, 51 were male and 50 were female. Each ethnic group had at least 12 normal subjects. Male-female data were analyzed separately and compared between groups. The palpebral fissure heights in Thai, Chinese, Thai-Malay, and Thai-Chinese males were 9.5, 9.0, 10.2 and 9.6 mm respectively, which demonstrated statistically significant differences between Thai-Malay versus Thai, and Thai-Malay versus Chinese. The palpebral fissure lengths were 30.4, 29.8, 30.5 and 30.5 mm, but without statistically significant differences. The marginal reflex distances were 3.2, 2.8, 3.7 and 3.1 mm respectively with a statistically significant difference only between Thai-Malay versus Chinese. The levator functions were 15.2, 15.2, 15.3 and 15.2 mm. The upper lid creases were 7.1, 4.0, 6.6, and 4.4 mm, statistically significantly different in Thai versus Chinese, Thai versus Thai-Chinese and Chinese versus Thai-Malay. The Hertel exophthalmometer measurements were 15.4, 16.3, 16.6 and 15.9 mm without statistically significant differences. The female measurements were overall similar to the male measurements, with some parallel differences between the groups. The eyebrow position in this age group was mostly at and above the orbital rim in both genders and all ethnic groups. An absence of upper lid crease and an epicanthal fold were found in significantly greater numbers in the Chinese group compared to the others, while parallel lid crease was significantly found in greater numbers in the Thai-Malay group than in the others. CONCLUSION Different eyelid characteristics in diferent ethnic groups are an important feature to note when planning for eyelid surgery. As there is a wide range of ethnic groups in Asia, with many differences in eyelid characteristics, it is important for the ophthalmologist to be aware of and understanding these anatomical variations in clinical assessment and treatment in Asians.