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Comparisons of anterior segment biometry between Chinese and Caucasians using anterior segment optical coherence tomography C K Leung, P-M Palmiero, R N Weinreb, et al. Br J Ophthalmol 2010 94: 1184-1189 originally published online July 7, 2010
doi: 10.1136/bjo.2009.167296
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Clinical science
Comparisons of anterior segment biometry between Chinese and Caucasians using anterior segment optical coherence tomography C K Leung,1 P-M Palmiero,2,3 R N Weinreb,4 H Li,1 Z Sbeity,2,3 S Dorairaj,2,3 D Leung,1 S Liu,1 J M Liebmann,2,3 N Congdon,1 D S Lam,1 R Ritch2,3 1
Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, P. R. China 2 Einhorn Clinical Research Center, The New York Eye and Ear Infirmary, New York, New York, USA 3 Department of Ophthalmology, The New York Medical College, Valhalla, New York, USA 4 Hamilton Glaucoma Center and Department of Ophthalmology, University of California, San Diego, La Jolla, California, USA Correspondence to Dr Christopher Kai-shun Leung, Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong;
[email protected] Accepted 15 November 2009 Published Online First 7 July 2010
ABSTRACT Purpose To compare anterior segment parameters between eyes of Chinese and Caucasians using anterior segment optical coherence tomography and to evaluate the association between these parameters and anterior chamber angle width between the two ethnic groups. Methods 60 Chinese and 60 Caucasians, 30 with open angles and 30 with narrow angles (defined as Shaffer grade #2 in $3 quadrants during dark room gonioscopy) in each group, were consecutively enrolled. One eye of each subject was randomly selected for imaging in a completely darkened room. Measurements, including anterior chamber depth (ACD), scleral spur-toscleral spur distance (anterior chamber width (ACW)), anterior chamber angle width, iris convexity and iris thickness, were compared between the groups. The associations between angle opening distance and biometric measurements were evaluated with univariate and multivariate regression analyses. Results There were no differences in age, axial length, anterior chamber angle measurements, pupil diameter and iris convexity between Chinese and Caucasians in both open-angle and narrow-angle groups. However, the ACD and ACW were smaller and the iris was thicker in Chinese. In the multivariate analysis, the ACD was the most influential biometric parameter for angle opening distance in both Chinese and Caucasians. After adjusting the effects of axial length, age and sex, ACD and ACW were significantly smaller in Chinese. Conclusions Chinese eyes had smaller ACD, smaller ACW and greater iris thickness than Caucasians. ACD was the most influential parameter in determining the angle width in both ethnic groups.
Primary angle closure (PAC) glaucoma is a leading cause of blindness in Asia.1 It has been estimated that 86.5% of patients with primary angle closure glaucoma would live in Asia in 2010.1 Whereas a shallow anterior chamber, short axial length and small corneal diameter have been considered risk factors for PAC,2e6 biometric differences between Chinese and Caucasians remain poorly understood.1 7 It is uncertain which biometric parameters are most influential in determining the angle width in different ethnic groups. Evaluation of the anterior chamber angle (ACA) in clinical practice has long relied on gonioscopy. However, precise measurement is attainable only with cross-sectional imaging techniques such as anterior segment optical coherence tomography (ASOCT). The ASOCT also allows measurement of 1184
the anterior chamber width (ACW; the scleral spurto-scleral spur distance), iris convexity and iris thickness, which cannot be quantified with gonioscopy or slit-lamp biomicroscopy. Investigating ocular biometric differences between Chinese and Caucasians may provide insight to understanding differences in prevalence of PAC. In this study, we measured and compared a number of biometric parameters (anterior chamber depth (ACD), axial length, ACA width, iris convexity, iris thickness, ACW) using ASOCT in Chinese and Caucasian subjects recruited in Hong Kong, PRC, and New York City, USA, respectively.
METHODS Subjects This is a clinic-based study. We consecutively enrolled 120 subjects (60 Chinese in Hong Kong, PRC, and 60 Caucasians in New York, New York, USA). At each site, 30 subjects with open angles and 30 with narrow angles were included. Except for cataract, these subjects had no evidence of ocular disease or glaucoma. The method for gonioscopy grading was standardised as follows. Indentation gonioscopy was performed using a Zeiss four-mirror gonioprism at 325 magnification with a short and narrow beam width (
