title: Ethnic variation in optic disc size by fundus photography.
abstract: OBJECTIVE
  To compare optic disc size among Caucasian, Chinese, African, Filipino and Hispanic subjects recruited from a university-based general ophthalmology clinic.
  
  
  METHODS
  In this retrospective cross-sectional study, optic disc size was calculated from fundus photographs. Differences in age, sex and spherical equivalent among the ethnic groups were examined with either Kruskal--Wallis test or Chi-square test. Ethnic differences in optic disc size were evaluated with linear mixed-effects regression models that adjusted for age, sex, spherical equivalent, glaucoma status, lens status and use of both eyes in the same subject.
  
  
  RESULTS
  Five hundred and seventy-four eyes of 305 subjects were analyzed. The mean and standard deviation of the optic disc size were 2.16 ± 0.41 mm(2) for Caucasian, 2.30 ± 0.56 mm(2) for Chinese, 2.31 ± 0.41 mm(2) for Filipino, 2.38 ± 0.40 mm(2) for African and 2.40 ± 0.38 mm(2) for Hispanic subjects. Age and spherical equivalent differed among the ethnic groups by Kruskal--Wallis test (p < 0.05). Sex differed among the ethnic groups by Chi-square test (p < 0.05). Ethnic differences in optic disc size were not observed among African, Hispanic, Filipino and Chinese subjects in linear mixed-effects regression analyses (p > 0.05). However, Caucasian differed from the other ethnicities in linear mixed-effects regression analyses (p < 0.05).
  
  
  CONCLUSIONS
  Optic disc size was significantly smaller in Caucasian compared to the other ethnic groups. Optic disc size differences among non-Caucasian ethnic groups were not significant.
authors.affiliation: Department of Ophthalmology, University of California, San Francisco , CA , USA .
authors.forename: Roland Y
authors.initials: RY
authors.lastname: Lee
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Kao
authors.forename: Toshimitsu
authors.initials: T
authors.lastname: Kasuga
authors.forename: Baotran N
authors.initials: BN
authors.lastname: Vo
authors.forename: Qi N
authors.initials: QN
authors.lastname: Cui
authors.forename: Cynthia S
authors.initials: CS
authors.lastname: Chiu
authors.forename: Robert N
authors.initials: RN
authors.lastname: Weinreb
authors.forename: Shan C
authors.initials: SC
authors.lastname: Lin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People; D044383:Black People; D003430:Cross-Sectional Studies; D005006:Ethnicity; D005260:Female; D005654:Fundus Oculi; D005901:Glaucoma / Q000208:ethnology* / Q000473:pathology*; D006630:Hispanic or Latino; D006801:Humans; D008297:Male; D008875:Middle Aged; D009898:Optic Disk / Q000033:anatomy & histology*; D010781:Photography; D012189:Retrospective Studies; D044465:White People