title: [Contrast visual acuity in adults with normal visual acuity].
abstract: OBJECTIVE
  To evaluate the contrast visual acuity (CVA) in Chinese normal adults and to study the effects of different contrast levels between the optotypes and background, age and sex on the CVA.
  
  
  METHODS
  It was a cross-sectional study. Three hundreds and fifty-three normal adults with age from 20 to 70 years were selected as the normal adults (naked visual acuity equal or more than 0.8, and equivalent sphere diopter -1.00 - +1.00 DS, astigmatic diopter -0.75 - +0.75 DC). After conducting eye and refractive examination, all examinee were received the CVA measurements in the different contrast levels between the optotypes and background (100%, 25%, 10% and 5%) in the dark room by the multifunction visual acuity chart. SPSS 18.0 software package was used for one-way ANOVA (analysis of variance), Spearman correlation and paired t test.
  
  
  RESULTS
  In the normal adults, CVA significantly decreased by the decrease of the contrast level between optotypes and background (F(OD) = 1317.21, P < 0.01; F(OS) = 991.09, P < 0.01; F(OU) = 1223.87, P < 0.01). In the same contrast level between optotypes and background, CVA significantly decreased by aging (F(100%CVAOD) = 10.86, P = 0.000; F(25%CVAOD) = 11.54, P = 0.000; F(10%CVAOD) = 7.63, P = 0.000; F(5%CVAOD) = 4.88, P = 0.001; F(100%CVAOS) = 15.26, P = 0.000; F(25%CVAOS) = 16.93, P = 0.000; F(10%CVAOS) = 8.33, P = 0.000; F(5%CVAOS) = 4.08, P = 0.003; F(100%CVAOU) = 11.87, P = 0.000; F(25%CVAOU) = 15.08, P = 0.000; F(10%CVAOU) = 11.71, P = 0.000; F(5%CVAOU) = 9.51, P = 0.000). CVA in the high contrast was similar between male and female, however, there was a significantly difference in CVA in the low contrast between male and female (F(100%CVAOD) = 0.341, P = 0.560; F(25%CVAOD) = 0.434, P = 0.510; F(10%CVAOD) = 5.615, P = 0.018; F(5%CVAOD) = 9.492, P = 0.002; F(100%CVAOS) = 0.212, P = 0.645; F(25%CVAOS) = 0.132, P = 0.716; F(10%CVAOS) = 4.588, P = 0.033; F(5%CVAOS) = 4.812, P = 0.029; F(100%CVAOU) = 0.775, P = 0.379; F(25%CVAOU) = 1.043, P = 0.308; F(10%CVAOU) = 8.555, P = 0.004; F(5%CVAOU) = 5.630, P = 0.018). A significantly correlation could be seen between the visual acuity of ETDRS and 100% CVA (r(OD) = 0.632, r(OS) = 0.536, r(OU) = 0.456, all P < 0.01). The 100% CVA was higher than the visual acuity of ETDRS (t(OD) = 20.70, t(OS) = 17.25, t(OU) = 23.47, all P < 0.01).
  
  
  CONCLUSIONS
  Age and the different contrast levels between optotypes and background significantly affect CVA. In the low contrast between optotypes and background, CVA in the female is better than in male.
authors.affiliation: Department of Ophthalmology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, China. zhaojialiang@medmail.com
authors.forename: Jie
authors.initials: J
authors.lastname: Li
authors.forename: Jia-liang
authors.initials: JL
authors.lastname: Zhao
mesh_terms: D000328:Adult; D000368:Aged; D015350:Contrast Sensitivity; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014787:Vision Tests; D014792:Visual Acuity; D055815:Young Adult