【摘要】 AIM: To evaluate the optic disc parameters in the three main ethnic groups of Malaysia (Malay, Chinese and Indian). Possible relationships between optic disc parameters and gender, intraocular pressure and axial length of eye were also studied.
METHODS: The study included 244 eyes of 122 subjects (61 cases with open angle glaucoma and 61 nonglaucomatous individuals) with clear ocular media. Magnification corrected measurements of optic disc diameters and area were done using Zeiss FF450 Plus fundus camera. Differences between the three ethnic groups were tested by using ANOVA. The association between factors such as gender, intraocular pressure and axial length of the eye, and the optic disc size was tested through Pearson's bivariate correlation analysis.
RESULTS: The overall mean vertical optic disc diameter was (1.96±0.20)mm, horizontal optic disc diameter was (1.84±0.20)mm and optic disc area was (2.84±0.56)mm2. Indians had larger optic disc area compared to Malay and Chinese. However, the difference was not statistically significant.
CONCLUSION: Optic disc size is larger in Malaysian population than Caucasians. Among the three ethnic groups, Indians have the largest optic disc size without any statistical difference.
KEYWORDS: optic disc diameter; optic disc area; Malay; Indian; Chinese
【关键词】 optic disc diameter optic disc area Malay Indian Chinese
INTRODUCTION
Despite its relatively small area compared to other countries in the region, Malaysia is uniquely featured with its multiracial population. Of a total population of about 23 millions in Census 2000, Bumiputra (majority of which are Malays) accounted for 65.1%, Chinese 26.0% and Indians 7.7%[1].
Clinical examination of the optic disc is an important part of the assessment of its health. In the literature, the normal area of optic disc were extensively studied in different countries among different races. The effect of ethnicity on optic disc size was well studied and documented in some countries. Previous studies have shown that AfroAmericans have larger discs compared to Caucasians[25]. Indians were found to have large optic disc size comparable with AfroAmericans[6,7]. Wang et al[8] also reported the optic disc size of Chinese people larger than that of Caucasians. So far, there is no data available in the literature on optic disc size of Malays.
The present study was conducted to determine the vertical and horizontal optic disc diameters and area in three ethnic groups of Malaysia (Malay, Chinese and Indian). The relations between optic disc size and gender, intraocular pressure, and axial length of the eye were also evaluated.
PATIENTS AND METHODS
This study included 244 eyes of 122 individuals (61 open angle glaucoma patients and 61 nonglaucomatous controlsrelatives of patients) selected from those attending the eye clinic, University of Malaya Medical Centre (UMMC), Kuala Lumpur between March 2006 and February 2007. The sample was planned to equally represent the three main ethnic groups of Malaysian populationMalay, Chinese and Indian. At the beginning of the study, inclusion criteria were circulated among colleagues in the eye clinic and medical technicians in the visual field room, and patients suitable for enrollment were selected on referral basis. The study protocol was approved by the medical ethics committee of the UMMC.
The study included glaucoma patients and nonglaucoma individuals attending the eye clinic in the study period, with clear ocular media that allowed taking clear fundus photos of both eyes. Patients with narrow angles and shallow anterior chambers were excluded to avoid the possibility of pupillary block when the pupils were dilated for fundus photography. Patients with opaque ocular media were also excluded because of problems in taking clear fundus photos of optic disc.
After obtaining informed consent, autokeratorefractometry (KR8100 autokeratorefractometer, Topcon Co., Tokyo, Japan) was performed. Axial length was measured by Ascan ultrasonography (EZ scan AB5500+, Sonomed, NY, US). The pupils were then dilated and a 30degree fundus photographs of both eyes were taken with fundus camera (FF 450 Plus, Zeiss Inc., Germany).
The refractive error, radius of corneal curvature, height and weight of the subject were entered into the fundus camera software to calculate the error of magnification for each eye. Corrected measurements of the vertical and horizontal disc diameters and optic disc area were recorded for each eye.
Statistical analysis was performed by using SPSS version 12. The mean of optic disc area was measured for the three ethnic groups, and the statistical significance of the differences between them was tested by ANOVA. The statistical strength of correlation was reported as correlation coefficient (r). All P values were two sided and were considered statistically significant when the values were less than 0.05.
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