title: Axial length/corneal radius ratio: association with refractive state and role on myopia detection combined with visual acuity in Chinese schoolchildren.
abstract: OBJECTIVE
  To evaluate the association between the AL/CR ratio and refractive state and explore the effectiveness of this ratio in the assessment of myopia, especially when combined with uncorrected visual acuity in schoolchildren among whom myopia is common.
  
  
  METHODS
  Cross sectional study. 4686 children from 6 primary schools, aged from 6 to 12 years were selected using the clustered-stratified random sampling method. Uncorrected visual acuity (UCVA), axial length (AL), corneal radius of curvature (CR), and cycloplegic refraction were tested. Refraction was measured as the spherical equivalent (SE).
  
  
  RESULTS
  3922 children were included in the analysis. The mean AL/CR ratio was 2.973±0.002, increased with age, and different in gender. The coefficients of correlations of the SE with the AL/CR ratio, AL, and CR were -0.811, -0.657, and 0.095, respectively. Linear regression showed a 10.72 D shift towards myopia with every 1 unit increase in the AL/CR ratio (P<0.001, r2 = 66.4%). The estimated SE values obtained by substituting the AL/CR ratio and gender back to the regression model that were within a difference of ±0.50 D in ATE/LER (allowable total error and limits for erroneous results) zones compared to the actual measured values was 51%. The area under the ROC curve of the AL/CR ratio, AL, and UCVA for myopia detection were 0.910, 0.822, and 0.889, respectively, and the differences between each pair were statistically significant (P<0.01). At a specificity of 90%, the sensitivities were 72.98%, 50.50%, 71.99%, and 82.96%, respectively, for the AL/CR ratio, AL, UCVA, and the combination of the AL/CR ratio and UCVA.
  
  
  CONCLUSIONS
  The AL/CR ratio was found to explain the total variance in SE better than AL alone. The effectiveness of the AL/CR ratio was statistically significantly better than UCVA for detecting myopia in children, and combining the two produced increased sensitivity without significantly decreasing specificity.
authors.affiliation: Department of Eye Disease Prevention, Shanghai Eye Disease Prevention & Treatment Center, Shanghai, China.
authors.forename: Xiangui
authors.initials: X
authors.lastname: He
authors.affiliation: Department of Eye Disease Prevention, Shanghai Eye Disease Prevention & Treatment Center, Shanghai, China; Department of Ophthalmology, Shanghai First Peoples' Hospital, affiliated Shanghai Jiaotong University, Shanghai, China.
authors.forename: Haidong
authors.initials: H
authors.lastname: Zou
authors.affiliation: Department of Eye Disease Prevention, Shanghai Eye Disease Prevention & Treatment Center, Shanghai, China.
authors.forename: Lina
authors.initials: L
authors.lastname: Lu
authors.affiliation: Department of Eye Disease Prevention, Shanghai Eye Disease Prevention & Treatment Center, Shanghai, China.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhao
authors.affiliation: Department of School Health, Baoshan Center for Disease Prevention and Control, Shanghai, China.
authors.forename: Huijuan
authors.initials: H
authors.lastname: Zhao
authors.affiliation: Department of School Health, Baoshan Center for Disease Prevention and Control, Shanghai, China.
authors.forename: Qiangqiang
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of Eye Disease Prevention, Shanghai Eye Disease Prevention & Treatment Center, Shanghai, China.
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Zhu
mesh_terms: D044466:Asian People; D002648:Child; D002681:China / Q000453:epidemiology; D003315:Cornea / Q000033:anatomy & histology* / Q000473:pathology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D009216:Myopia / Q000175:diagnosis / Q000453:epidemiology; D015995:Prevalence; D012372:ROC Curve; D012029:Refraction, Ocular; D014787:Vision Tests; D014792:Visual Acuity