The Study On Refractive Development Index And Its Association With Physical Development In Primary And Middle School Students

ObjectiveIn the context of the Implementation Plan for the Prevention and Control of Myopia for Children and Adolescents which was issued by the Ministry of Education and National Health Commission of the People's Republic of China,the purpose of current study is to explore the correlation between ocular biometrics and refraction on the basis of describing the frequency distribution of ocular biometrics of primary and secondary school students and their differences by age and gender.And further explore associations between anthropometric indicators and both refraction and ocular biometrics to enrich the understanding of the current etiology of myopia.MethodsParticipants were initially recruited using a stratified,clustered,random sampling method.All selected students were invited,but participation in this study was voluntary.Ocular biometrics,such as axial length(AL),central corneal thickness(CCT),anterior chamber depth(ACD),lens thickness(LT),vitreous chamber depth(VCD),and corneal radius of curvature(CR),were measured with a low-coherence optical reflectometry device(Lenstar LS900;Haag-Streit AG,3098 Koeniz,Switzerland)in both eyes before pupil dilation.In addition,the AL/CR ratio was calculated.Cycloplegia was induced following standardized protocols,participants with full cycloplegia underwent autorefraction using an auto-kerato-refractor(Canon Autorefractor RK-F1,Tokyo,Japan),and 3 consecutive measurements were taken in both eyes.The mean value of 3 valid measurements was calculated for spherical equivalent refraction(SER).The SER was calculated as the spherical refraction + 1/2 of the cylindrical refraction.Myopia was defined as an SER of ?-0.50 D.Physical development indicators such as height,weight and BMI were measured by school health care teachers in accordance with the relevant standards in the instruction manual of national survey in Physique and health of Chinese schoolchildren(2014).Information on social-demographic characteristics and potential risk factors for school myopia,such as age,gender,parental myopia,family income,reading and writing distance,and time spent outdoors,was collected by questionnaires.Multiple linear regression analysis was performed to explore the associations between ocular biometrics and refraction,and associations between anthropometric indicators and both refraction and ocular biometrics.ResultsA total of 566(88.71%,566/638)primary and secondary school students aged 6-14 years were included in this study.Complete survey data was obtained from all subjects.The overall myopia prevalence of the subjects was 62.19%(352/566,95% CI: 58.18%,66.20%).The prevalence of myopia in the 6-8,9-11 and 12-14 age groups was 42.93%,61.90%,and 85.47%,respectively(P<0.01).There was no significant difference in the prevalence of myopia between boys and girls(62.58% vs.61.74%,P=0.84).According to the P-P diagram,the distribution of SER,AL,CCT,ACD,LT,VCD,CR and AL/CR ratios showed a normal distribution.AL,ACD,VCD,and AL/CR ratios increased with age,and LT decreased with age,but there was no significant difference between CCT and CC in each age group(P values were 0.63 and 0.42,respectively).AL,CCT,ACD,VCD,CR and AL/CR ratios were higher in boys than that in girls,but LT was higher for girls than boys(All P values were less than 0.05).The regression model based on the associations between refraction and ocular biometrics showed that after controlling for gender,age and height,more negative refractions were independently correlated with deeper VCDs(regression coefficient ?=-1.98,P<0.01),thicker LTs(?=-3.42,P<0.01),deeper ACDs(?=-0.55,P<0.01),and smaller CRs(?= 4.53,P<0.01).Moreover,VCD,CR,and LT were the most important ocular determinants of refraction,both in overall and age-specific analysis.These three combinations could explain 78% of the refractive variation in the whole participants.The regression model based on the associations between anthropometric indicators and both refraction and ocular biometrics showed that,in general,both higher heights(?=-0.28,P<0.01)and heavier weights(?=-0.24,P<0.01)were independently associated with more negative refractions after controlling for age,gender,parental myopia,family income,reading and writing distance,and time spent outdoors.Furthermore,age-specific results demonstrated that height was independently associated with refraction in only 6-to 8-year-old and 9-to 11-year-old participants.Especially from 9 to 11 years of age,higher heights in schoolchildren were associated with longer ALs(+0.24 mm,P<0.01),deeper VCDs(+0.23 mm,P<0.01),higher AL/CR ratios(+0.03,P<0.01),and more negative refractions(-0.42 D,P<0.01)in their eyes.The association pattern in weight was almost the same as that in height in this age group.However,in the 12-14 age group,we did not find any statistically significant association between height,weight,or BMI and both refraction and ocular biometrics.ConclusionCompared with the low-age group,subjects in the high-age group had larger parameter dimensions except for LT(smaller)and CCT and CR(both unchanged).Boys had larger ocular dimensions than girls except for LT(smaller).VCD,CR,and LT were the most important ocular biological parameters of refractive state.Height and weight remained independently related to refraction and various ocular biometrics during the early period of adolescent growth after adequately controlling for covariates,which could support the idea that a shared mechanism may regulate the coordinated growth of body and eye size in children.