Purpose: Increased levels of outdoor light have been found to be associated causally with decreased rates of myopia. The goal of this study was to measure the effect of indoor nursery school light intensity on refraction of preschool children in Israel. Methods: A total of 1596 children aged 4 to 5 years from 27 nursery schools were examined. Light intensity was tested with a luxmeter device (Lux) inside and outside the nursery school. Noncycloplegic refractions were measured with the PlusOptix vision A09 screening device. Data analysis was performed using Pearson coefficients, chi-square tests for proportions and ANOVA tests by tertiles of illuminance.Results: This study included 1131 kindergarten children with a mean age of 4.87 AE 0.33 years, of which 571 were female (50.5%). The mean light intensity of the low, medium, and high intensity groups differed significantly (ANOVA P < 0.001) at 359 AE 2.64 lux (range 264-431), 490 AE 2.21 lux (range 432-574), and 670.76 AE 3.73 lux (range 578-804), respectively. Mean spherical equivalent (SE) was þ0.56 AE 0.03D for the low-intensity group, þ0.73 AE 0.03D for the medium-intensity group, and þ0.89 AE 0.03D for the high-intensity group (ANOVA P < 0.001). The low-intensity group had 42.1% of children with zero refraction or less, while the high-intensity group had 19.3%. Conclusions: In the nursery schools, lower amounts of illumination were associated with less hyperopic refractive error. As the low hyperopic reserve is a risk factor for developing myopia, this finding needs to be followed up to establish whether this association reflects a causal relationship, which could be modulated for the prevention of myopia.