Myopia is a common disease of the eye with increasing prevalence in the Western World as well as in South East Asia where 60-90% of the children are affected. High myopia is associated with an increasing risk of sight threatening complications such as retinal detachment, glaucoma, macular choroidal degeneration and myopic choroidal neovascularization. In myopia the eye is elongated compared to an emmetropic eye. If the elongation of the eye can be controlled the progression of myopia can be controlled. Asian studies have shown reduction in axial length growth by 36-46% in children using orthokeratology contact lenses (OKL). OKL are custom fit, form stable lenses. During sleep the cornea is reshaped creating an emmetropic vision during the day, so no glasses or contact lenses are needed. Twin and family studies have shown a high heritability for the development of myopia, and more than 40 genetic loci have been identified indicating that the effect of OKL in Asian children might not be the same in North European children which is why we want to execute a similar study on North European children.