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Jane E. Gwiazda, Li Deng, Ruth E. Manny, COMET study group; Seasonal Differences in the Progression of Myopia in COMET Children. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2309.
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To investigate seasonal differences in the progression of myopia in children enrolled in the Correction of Myopia Evaluation Trial (COMET).
COMETenrolled 469 ethnically diverse children aged 6 to <12 years with spherical equivalent refractions (SER) between -1.25 and -4.50 D. 235 were randomly assigned to progressive addition lenses (PAL) with a +2.00 addition and 234 to single vision lenses (SVL). The main outcome was myopia progression by cycloplegic autorefraction (Nidek ARK 700A) collected annually. Myopia also was measured at 6-month intervals by non-cycloplegic autorefraction. Only right eye data collected in the first year from children with non-cycloplegic measurements within +/- 35 days of their targeted 6- and 12-month visit dates were used in the analyses. To standardize the duration between visits, semi-annual progression rates were calculated by first dividing the change in SER between 2 consecutive semi-annual visits by the actual number of days between the 2 visits, and then multiplying by 182.5. Additional analyses evaluated data collected in the second and third years of the study. Seasons were classified as either winter (October through March) or summer (April through September) based on the month in which the mid-point between two visits fell. The seasonal difference was tested using a linear mixed model adjusting for demographic variables, baseline refraction, and treatment group.
Overall, for the 386 children with semi-annual visits close to their target dates, the mean progression rate in winter was -0.35 ± 0.36 D and in summer was -0.14 ± 0.34 D, a statistically significant difference of 0.21 D (p<0.0001). The seasonal differences were similar in the PAL (0.19 D) and SVL (0.22 D) groups (p=0.60). The same seasonal pattern was found by age, gender, and ethnicity. The seasonal difference was slightly higher for children with their first visits in the winter (n =147; 0.26 D difference) compared to the summer (n=239; 0.17 D difference), although not statistically significant (p=0.10). Similar seasonal differences were found in each of the following 2 years of the study.
In the COMET cohort progression of myopia was significantly greater in winter than in summer. More near work in winter months and/or more outdoor activity in summer may account for these seasonal differences in progression.
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