Changes Of Refraction And Ocular Biometric Parameters Of Medical University Freshmen:A 2-year Follow-up Study

PurposeThe purpose of this study is to observe the refraction situation of medical university freshmen.Sequentially,the changes of their refraction and ocular biometric parameters during their undergraduate study were investigated,as well as the relevant risk factors of this potentialMethodsThis is a prospective,follow-up study.Part of freshmen of grade 2016 in Tianjin Medical University were enrolled and followed up using a stratified cluster random sampling.A total three-time-measurement was conducted in their first,second and third grades,respectively.Then spherical equivalent refraction(SER),axial length(AL),central corneal thickness(CCT),anterior chamber depth(ACD),lens thickness(LT),corneal radius(CR),and the ratio axial length/ratio radius(AL/CR)in different times have been acquired.In the first cross-section study,we investigated the prevalence of myopia and the characteristics of ocular biometric parameters in freshmen.The difference between SER and ocular biometric parameters in different gender was analyzed by independent t-test.One-way analysis of variance(ANOVA)and least significant difference t-test(LSD t-test)were used to compare the characteristics of ocular biometric parameters in different refractive error groups.In follow-up study,the Repeated Measures Analysis of Variance(RM-ANOVA)was used to observe the changes of SER and biometric parameters of three years.In the third year,questionnaire was introduced to investigate the status of eye using of the past two years among students,and the outcomes of this questionnaire were concerned as independent variables of the following data analysis.According to the changes of axial length,subjects were divided into two groups:1.larger increase in AL;2.smaller increase in AL.Binary logistic regression analysis was established with an odds ratio(OR)to identify the risk factors associated with refractive changes in this population of university.When the p value<0.05,the differences were considered to be statistically significantResultsThe exclusion criteria of subjects were current eye disease or previous eye surgery.At first year,648 individuals were analyzed in our research,including 262 males and 386 females,with an average age of 18.35±o.68y(16-22y).Mean SER of males was-4.18 ± 2.54D,and that of females was-4.28 ± 2.53D.There was no significant difference between the two genders(p>0.05).The prevalence of myopia was 92.44%,and high myopia was 23.61%.Relatively steady longer axial length and deeper anterior chamber were found in male,while steeper cornea was found in female(p<0.05).Excepted for sample size missing,526 students were finally enrolled in follow-up study,including 213 males and 313 females.Diopter of spherical(DS)and SER showed a significant myopic shift about 0.38D(p<0.05),and the astigmatism did not change significantly(p>0.05).There was no statistical difference in ASER between two genders during these two years(P>0.05).Although the prevalence of myopia didn't show significant changes,the prevalence of high myopia increased significantly to 28.33%.Significant differences were shown in the increase of AL,the thinning of CCT and the thickening of LT(all p values<0.05),while ACD had no significant difference(p>0.05)in these two years.AL growth in female was significantly larger than male(p<0.05),and the other changes were not statistically significant between male and female.Binary logistic regression analysis showed that the students maj oring in literary in medical university had less increase in axial length(OR=0.35,95%Cl:0.13-0.96),while female(OR=1.24,95%Cl:1.03-1.48),long?term exposure to online games(OR=2.09,95%Cl:1.33-3.29)and parental myopia(OR=1.98,95%Cl:1.26-3.09)could lead to larger axial length increasing in undergraduates(p<0.05).The baseline of axial length,near work time excepting daily courses,non-game electronic products using time,and visual fatigue score had no significant effect on the growth of AL in undergraduates(p>0.05).ConclusionsThere was a myopic shift of refractive error of students during their undergraduated program in medical university.While there was no statistically significant difference in their astigmatism.Changes in ocular biometric parameters have been shown as increase of axial length,decrease of central corneal thickness,and increase of lens thickness.Students whose maj ored in arts and less involved in online games showed less refractive changes.