Defocus (DIMS) Spectacles Versus Ortho-K Lenses (OKL) for Slowing Myopia Progression in Danish Children Aged 6-12 Years.

The purpose is to compare the myopia control efficacy of Ortho-K lenses (OKL) and Defocus (DIMS) spectacles in Danish myopic children aged 6-12 years. It is a clinical randomized non-inferiority trial, where the participants are randomly assigned to either OKL or DIMS spectacles. The participants are followed during 18 months of therapy. The hypotheses: * There is no statistically significant difference between the myopia control efficacy between OKL and DIMS spectacles. * Larger pupil size is positively correlated to treatment efficacy for both devises. * Increasing choroidal thickness during early treatment is positively correlated to treatment efficacy for both devises. * There is no difference in vision related quality of life between the two groups.