A Follow-up Study On Distribution And 5-year Progression Of Astigmatism In School-age Children In Mojiang County Of Yunnan Province

Objective:To investigate the distribution,the prevalence and and the cumulative 5-year incidence rate of refractive astigmatism and corneal astigmatism in 7-8 years old school-age children in MoJiang County of yunnan province;to observe longitudinally changes in the distribution of astigmatism,astigmatism diopter and ocular biometry parameters over five years;to analyze the correlation between astigmatism and changes in the ocular biometry parameters;to explore the law of astigmatism change in school-age children.Methods:This was a cohort study.Based on the results of cross-sectional screening,a 5-year follow-up survey was conducted for 2,432 students which 7-8 years old in 12 primary schools in MoJiang County of yunnan province.Cycloplegic autorefraction was performed(TOPCON RM-8000;tropicamide&phenylephrine opthalmic solution).Refractive astigmatism(RA)and the total axis of astigmatism were obtained.The Len-Star optical biometer was used to measure the ocular biometry parameters(AL、LT、Kf、Ks、ACD、CCT),and obtain the corneal astigmatism(CA)and the axis of astigmatism.The changes of refractive astigmatism,corneal astigmatism and ocular biometry parameters over five years were calculated,and the correlation between astigmatism and changes in ocular biometry parameters was analyzed.The Thibos vector analysis method was used to analyze the vector characteristics of refractive astigmatism and corneal astigmatism,and calculated the astigmatism vector parameters J0,J45 and the five-year changes.The SPSS26.0 statistical software was performed statistical analysis on the right eye data of all subjects.Results:1.A total of 2,432 students completed the examination in the baseline survey,with a mean age of 7.7 years.There were 2169 students in the fifth follow-up survey(follow-up rate 89.2%),one of them was not included in the study due to trauma to the right eye during the follow-up period..In the fifth year,2168 students were incorporated into study the study,and 2095 students completed the measurement of ocular biometry parameters.2.The axes of refractive astigmatism(RA)were mainly with the rule.For RA,the proportion of with-the-rule astigmatism increased in the fifth year(baseline:79.9%;5th follow-up:88.6%),the proportion of against the rules astigmatism(baseline:9.8%;5th follow-up:5.6%)and oblique astigmatism(baseline:10.3)%;5th follow-up:5.8%)were decreased.The prevalence of RA(≥0.75D)at baseline was 8.1%.The cumulative 5-year incidence rate of RA was 11.2%.3.RA increased by 0.09D over 5 years in this cohort.Within five years,38.4%of students had no change in RA,38.8%of students’ RA increased less than 1D,2.1%of the students’ RA increased more than 1D,20.2%of the students’ RA decreased less than 1D,and 0.5%of the students’ RA decrease more than 1D.4.The axes of corneal astigmatism(CA)were mainly with the rule.For CA,the proportion of with-the-rule astigmatism increased in the fifth year(baseline:92.9%;5th follow-up:95.4%),the proportion of against the rules astigmatism was decreased(baseline:3.9%;5th follow-up:1.3%),the proportion of oblique astigmatism was similar to baseline(baseline:3.2%;5th follow-up:3.3%).The prevalence of CA(≥0.75D)at baseline was 67.0%.The cumulative 5-year incidence rate of CA was 41.1%.The prevalence of CA was higher in girls than boys(p<0.05).5.CA increased by 0.08D over five years in this cohort.Within five years,0.9%of students had no change in CA,43.5%of students’ CA increased less than 1D,1.9%of the students’ CA increased more than 1D,52.9%of the students’ CA decreased less than 1D,and 0.8%of the students’ CA decrease more than 1D.6.Within five years,Kf decreased and Ks increased among Students with RA and CA increased,those with astigmatism increased more than 1D had the largest increase in Ks and the fastest increase in axial length.Kf and Ks decreased for those with RA decreased and those with CA decreased less than 1D over five years.Those with CA increased more than 1D had the largest increase in Ks and the largest decrease in Ks.The five-year changes in RA and CA were positively correlated with AL growth,LT growth,and Ks changes,and negatively correlated with ACD shallow and Kf changes.7.The results of astigmatism vector analysis showed that RAJO and CAJO increased by 0.058D and 0.048D,absolute RAJ45 and CAJ45 increased by 0.002D and 0.024D over five years.Myopic children at baseline had a higher RAJO progression than nonmyopes,and the difference was statistically significant(P=0.001).The absolute CAJ45 progression of girls was higher than boys,and there was a gender difference(P=0.003).Conclusions:1.The distribution of refractive astigmatism and corneal astigmatism were mainly with the rule in 7-8 years old school-age children in MoJiang County of yunnan province.The prevalences of RA and CA(≥0.75D)were 8.1%and 67.0%.The cumulative 5-year incidence rate of RA and CA were 11.2%and 41.1%.2.The RA and CA had an increasing trend with age,and with-the-rule astigmatism had a tendency to convert to against-the-rule astigmatism.The 5-year fluctuation of astigmatism was mainly within 1D.3.The increase of RA and C A was related to the increase of AL,the decrease of Kf,the increase of Ks,the increase of LT,and the shallow of ACD.