Relation of childhood myopia progression rates to time of year

One potential method for assessment of the effect of near work on childhood myopia progression is to compare progression rates overtime spans that have differing near-point demands.

Myopia progression rates were calculated for a 6-month period during the school year (called school rate in this article) and for a 6-month period that included the 3 months of summer vacation (called summer rate). Data used for analysis were right eye spherical equivalents from manifest subjective refractions of 27 children in a longitudinal study at Northeastern State University in Oklahoma, and 15 children in a longitudinal study at Indiana University. All subjects wore single-vision spectacle lenses.

The mean summer rate for the 42 subjects was -0.39 diopters per year (D/yr) (SD = 0.46). The mean school rate was -0.72 D/yr (SD = 0.57). The rates during the two periods were significantly different by two-tailed paired t-test (p = 0.006).

The differing amount of nearpoint activity during the school year and the summer is a potential explanation for the different rates of myopia progression during those two time periods.