Abstract
Purpose: :
To investigate whether relative peripheral refraction (RPR) changes during myopic progression are symmetric and if RPR is associated with myopic progression in children.
Methods: :
Cycloplegic autorefraction was performed on the right eye of 42 myopic children between 6-11 years of age. Children were then seen every 6 months for two years, and all children wore single vision spectacles. Aberrations were measured after cycloplegia along the line of sight, 30º nasally, temporally, and superiorly, and 20º inferiorly on the retina. Aberrometry-based RPR was calculated for each peripheral retinal location using a previously validated method. A repeated-measure ANCOVA controlling for the progression of myopia was used to determine if there were differences in RPR over time (baseline and 24 months) and if any changes in RPR found with myopic progression were symmetric (i.e., if all measured retinal locations changed similarly). Linear regression was used to determine if baseline RPR could predict the progression of myopia. Control variables included baseline age and gender.
Results: :
The mean age (± SD) and spherical equivalent refractive error (SER) of the children at baseline were 10.1 ± 1.5 years and -2.05 ± 0.88 D, respectively. The two-year mean myopic progression was -0.84 ± 0.63 D. At baseline, RPR differed by location (p < 0.0001): hyperopic in the horizontal meridian (nasal = 0.56 ± 0.62 D; temporal = 0.61 ± 0.72 D) and myopic in the vertical meridian (superior = -0.45 ± 0.88 D; inferior = -0.45 ± 0.80 D). Differences in RPR over the two-year period depended on the amount of myopia progression during that period (p < 0.0001), but not on retinal location (p = 0.77; i.e., changes in RPR over time were symmetrical); therefore, RPR was averaged across locations. Gender was not a significant predictor of myopic progression (p = 0.38). Myopia progression over 2 years was less for older children (β = 0.26 D less myopic progression over 2 years per year of age at baseline; p < 0.0001). The amount of myopia progression over the two-year period was greater in children with more relative peripheral hyperopia at baseline (β = -0.27 D more myopic progression over 2 years per diopter of relative peripheral hyperopia; p = 0.04).
Conclusions: :
Changes in RPR with myopic progression were symmetric. More hyperopic RPR was associated with greater myopic progression. These results suggest that large amounts of relative peripheral defocus would be necessary to have a clinically meaningful influence on myopia progression.
Clinical Trial: :
http://www.clinicaltrials.gov NCT00335049
Keywords: refractive error development • myopia • clinical (human) or epidemiologic studies: natural history