Two-year longitudinal change in choroidal and retinal thickness in school-aged myopic children:exploratory analysis of clinical trials for myopia progression

Background:With increasing axial length(AL)and myopia progression,the micro-structure of the retina and choroid gradually changes.Our study describes the longitudinal changes in retinal and choroidal thickness in school-aged children with myopia and explores the relationship between changes in choroidal thickness and myopia progression.Methods:An exploratory analysis of a randomized trial was performed.Children(n=168,aged 7 to 12 years)with myopia from-0.75 diopter(D)to-4.00 D were enrolled in this prospective longitudinal study.Cycloplegic refraction,AL,retinal and choroidal thicknesses were measured at baseline and at 1-and 2-year follow-ups."Rapid progression myopia"was defined as increasing in myopia>1.00 D and'"stable progression myopia"was≤1.00 D during the 2-year follow-up.Factors affecting the changes in choroidal thickness were analysed using linear mixed models.Results:AL significantly increased by 0.67±0.24 mm with a myopic shift of-1.50±0.64 D over the 2 years.The overall retinal thickness increased from 251.12±15.91μm at baseline to 253.47±15.74μm at the 2-year followup(F=23.785,P<0.001).The subfoveal choroidal thickness decreased from 231.03±54.04μm at baseline to 206.53±59.71μm at the 2-year follow-up(F=73.358,P<0.001).Choroidal thinning was significantly associated with AL elongation(β=-43.579μm/mm,P=0.002)and sex(β=-17.258,P=0.001).Choroidal thickness continued to decrease in subjects with rapid progression(F=92.06,P<0.001)but not in those with steady progression(F=2.23,P=0.119).Conclusion:Significant choroidal thinning was observed and was associated with rapid progression and sex.These findings indicate a need to understand the role of the choroid in eye growth and myopia development.Synopsis/Precis:The macular choroidal thickness of myopic children is relevant to different degrees of myopic progression in this 2-year longitudinal study.These findings suggest that control of choroidal thickness might work to regulate human ocular growth.