Myopia is the world's most occurring eye disease, and is usually caused by increasing length growth of the eye. Myopia in itself leads to great personal and societal costs and in addition it also lead to secondary eye disorders such as retinal detachment, glaucoma and cataract. The growth of the eye length is principally developed until mid-childhood, witch is why it is these years witch is most valuable to investigate the underlying factors of the development of myopia.