A longitudinal study of oculometric parameters and the risk factors for myopia in students from primary schools

Abstract

Objective To compare the changes in oculometric parameters of students from different grades in 2009 and 2010, and to identify the distinct characteristics and proportion of students with (axial length/corneal radius) AL/CR＞3.Methods It was a prospective investigative study.All students from grades 1 and 4 from primary schools in the Yangfangdian district of Beijing were chosen for 2 years of observation (2009 and 2010).They were examined with the standard logarithmic visual acuity (VA) chart for VA and IOL Master for ocular components.The measures for right eyes were in agreement.Data were analyzed by using independent samples t test,paired t test,and chi-square test.Results Students in grade 1 (n=1282,mean age 6.44±0.52 years) and grade 4(n=1688,mean age 9.25±0.46 years) were examined in 2009; the number of corresponding grades in 2010 were 1210 (mean age 7.44±0.51 years) and 969 (mean age 10.25±0.48 years) respectively.From 2009 to 2010,students from grades 1 and 4 had significantly worse VA (t=-15.54,-10.50,P＜0.01),longer axial length (AL,t=24.21,25.84,P＜0.01) and larger AL/CR (t=11.58,9.77,P＜0.01),but there were no differencesin K,corneal astigmatism (CA) or CR.The boys from different grades had longer AL and CR and smaller K than the girls (P＜0.01).The proportion of students with AL/CR＞3 in grades 4 was higher than those in grades 1 (x2=489.7, 319.9,P＜0.01),during 2009and 2010, and the proportion of students with AL/CR＞3 in 2010 was higher than those in 2009 (x2=140.2,40.1,P＜0.01).Conclusion We found that VA and oculometric parameters were affected as children aged.As age increased, the proportion of students with myopia risk factors increased,resulting in a corresponding increase in the development of myopia. Analysis of the proportion of people with AL/CR＞3 in different groups can be used to estimate the risk factors for myopia and can be generalized for future studies. Key words: Myopia; Prospective studies; Axial length; Corneal radius; Axial length/corneal radius