A Comparison On The Effect Of Two Kinds Of Optically Designed Orthokeratology Lens For Moderate Myopia In Adolescents

Purpose:To observe the difference of orthokeratology lens with different optical designs CRT and VST in control of moderate myopia adolescents.Methods:A retrospective cohort study.A total of 72 moderate myopia adolescents aged8-16 years were fitted with CRT and Hiline orthokeratology lens and spectacle respectively.The axial length was measured before enrollment and 1 year,and the corneal topography was measured before enrollment and 3 months.Relative refraction is defined as subtracting the corneal apex refraction from the peripheral refraction.The relative refraction of cornea was calculated before and after 3 months of lens wearing.SCPC（3mm）was defined as the sum of changes in relative corneal refraction within a diameter of 3mm,and SCPC（7.2mm）was defined as the sum of changes in relative corneal refraction within a diameter of 7.2mm.The ANOVA was used to compare the changes of axial length in CRT group,VST group and spectacle group for 1 year.Multiple linear regression was used to analyze the influencing factors of axial length growth.Results:The axial length changes of CRT group,VST group and spectacle group for 1year were（0.25±0.18）mm,（0.08±0.16）mm and（0.40±0.21）mm,respectively.There were significant differences in the axial length changes of the three groups for 1 year（P<0.05）.The increase of axial length in CRT group and VST group was less than that in the control group,and the increase of axial length in the VST group was less than that in the CRT group in 1 year.The SCPC（3mm）in CRT group and VST group were（-0.07±1.24）D·mm and（1.44±1.28）D·mm,respectively,and the SCPC（3mm）in the VST group was larger than that in the CRT group,the difference was significant（P<0.0001）.The SCPC（7.2mm）in the two groups were（8.22±5.96）D·mm and（12.49±6.36）D·mm,respectively.SCPC（3mm）in the VST group was higher than that in the CRT group,and the difference was significant（P=0.018）.There was no significant difference in the changes of corneal apex refraction and the maximum value of corneal relative refraction（Rmax）between CRT and VST groups.The changes of horizontal coma in the CRT group and VST group were（0.357±0.704）μm and0.721（0.244,1.481）μm,respectively,and the differences were significant（P=0.043）,while the changes of HOA RMS,Trefoil 0°,Vertical coma,Trefoil 30°,Spherical aberration in the two groups were not significant.Multiple linear regression analysis,including age,initial axial length and SCPC（3mm）,showed that 1-year axial length change was significantly correlated with age（standardizedβ=-0.453,P<0.001）and SCPC（3mm）（standardizedβ=-0.309,P=0.013）.There was no correlation with baseline axial length（standardizedβ=0.078,P=0.521）.The regression equation for predicting1-year axial changes using SCPC（3mm）and age was acceptable（adjusted R²=0.341）and significant（F=13.653,P<0.001）.The regression equation using SCPC（3mm）(X₁)and baseline age（X₂）as functions for 1-year axial growth（Y）was Y=0.737-0.04X₁-0.049X₂.Conclusion:The two optical designs of orthokeratology lens are effective in controlling the progression of myopia,and they are better than the spectacle group.The CRT group and VST group have different effects on control of moderate myopia in adolescents,and VST group is superior CRT group.Baseline age and the sum of corneal refractive changes within diameter 3mm of cornea were the factors affecting axial growth.