Seasonal variation in myopia progression and axial elongation: an evaluation of Japanese children participating in a myopia control trial.
OBJECTIVE
To investigate the seasonal variations in myopia progression and axial elongation in Japanese children.


METHODS
Ninety-two children who were enrolled in a myopia-control trial and wearing single vision or progressive addition lenses were included in the analyses (mean ± SD age 11.4 ± 1.7 years, mean spherical equivalent refractive error -4.40 ± 1.38 D). Refractive error and axial length were measured every 6 months for 1.5 years by non-cycloplegic autorefraction and partial coherence interferometer, respectively. Myopia progression and axial elongation for each 6-month interval were calculated by subtracting the measure at the end of the interval from that at the beginning. Seasons were classified as summer, winter or others, based on mid-day of the 6-month period between visits.


RESULTS
Myopia progression was not significantly influenced by the season. After adjusting study groups (type of spectacles), years and age at the baseline, the mean (±SE) myopia progression was 0.35 ± 0.04 D for summer, 0.28 ± 0.06 D for winter and 0.38 ± 0.04 D for the others. In contrast, axial elongation was significantly influenced by the season, and the mean axial elongation was 0.137 ± 0.010 mm for summer, 0.170 ± 0.013 mm for winter and 0.163 ± 0.008 mm for the others. The seasonal variation in axial elongation, however, was smaller than that previously reported overseas.


CONCLUSIONS
In Japanese children myopia progression did not slow in summer. Although axial elongation slightly decreased in summer, myopia progression seems to be fairly stable throughout the year.
Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan. miyuki_1215@hotmail.com
Miyuki
M
Fujiwara
Satoshi
S
Hasebe
Risa
R
Nakanishi
Kohhei
K
Tanigawa
Hiroshi
H
Ohtsuki
D000293:Adolescent; D044466:Asian People; D058452:Axial Length, Eye / Q000473:pathology*; D002648:Child; D018592:Cross-Over Studies; D018450:Disease Progression; D004311:Double-Blind Method; D005139:Eyeglasses; D005260:Female; D006801:Humans; D007564:Japan; D008297:Male; D009216:Myopia / Q000503:physiopathology* / Q000628:therapy*; D011446:Prospective Studies; D012621:Seasons