title: Ethnic variations in myopia and ocular biometry among adults in a rural community in China: the Yunnan minority eye studies.
abstract: OBJECTIVE
  To determine the prevalence of myopia and ocular biometry in population-based samples of ethnic Yi and Han people living in an inland rural community in China.
  
  
  METHODS
  A random cluster sampling strategy was used to select ethnic Han and Yi adults aged 50 years or older living in Yunnan. Refractive error was determined by subjective refraction and ocular biometric parameters, including axial length (AL), anterior chamber depth (ACD), vitreous chamber depth (VCD), and lens thickness (LT), which were measured using an Echoscan.
  
  
  RESULTS
  Adults of Yi ethnicity had lower prevalence of myopia (10.3% vs. 8.1%; P = 0.02) and high myopia (2.3% vs. 1.6%; P = 0.10) than their counterparts of Han ethnicity. The prevalence of myopia increased with age (P for trend < 0.05), whereas the mean AL did not differ significantly among age groups in both ethnic groups (both P for trend > 0.05). In multivariate analysis, time spent outdoors was associated with myopia (P = 0.003) and AL (P < 0.001) but not high myopia (P = 0.33). No interaction effect was detected between ethnicity and other risk factors on myopia (all P > 0.05). Adjustment for lens nuclear opacity score reduced the excess prevalence of myopia in Han ethnicity by 37.5%.
  
  
  CONCLUSIONS
  There was little evidence showing that ethnic disparities existed in the prevalence and risk factors between the major and minor ethnic groups living in the same communities in rural China. The "cohort effect" on myopia observed in many other populations was not seen in this study.
authors.affiliation: Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases School of Public Health, Medical College of Soochow University, Suzhou, China.
authors.forename: Chen-Wei
authors.initials: CW
authors.lastname: Pan
authors.affiliation: First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Chen
authors.affiliation: First Affiliated Hospital of Kunming Medical University, Kunming, China.
authors.forename: Xun
authors.initials: X
authors.lastname: Sheng
authors.affiliation: First Affiliated Hospital of Kunming Medical University, Kunming, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: First Affiliated Hospital of Kunming Medical University, Kunming, China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Niu
authors.affiliation: First Affiliated Hospital of Kunming Medical University, Kunming, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Kunming Medical University, Kunming, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Wei
authors.affiliation: First Affiliated Hospital of Kunming Medical University, Kunming, China.
authors.forename: Yuansheng
authors.initials: Y
authors.lastname: Yuan
authors.affiliation: First Affiliated Hospital of Kunming Medical University, Kunming, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Zhong
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People; D001699:Biometry; D002681:China / Q000453:epidemiology / Q000208:ethnology; D016000:Cluster Analysis; D005123:Eye / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009216:Myopia / Q000453:epidemiology* / Q000208:ethnology / Q000503:physiopathology; D015995:Prevalence; D012029:Refraction, Ocular / Q000502:physiology; D012307:Risk Factors; D012424:Rural Population