Abstract
The major genetic and environmental factors responsible for myopia, its increasing incidence, and the mechanism through which each acts have been unknown. Insight into common disorders is sometimes gained from rare, more severe versions of the condition in which the understanding of mechanisms is more accessible. That has proven true for myopia. Mutations associated with common myopia were identified by following clues from the recent identification of photopigment gene mutations at MYP1, the first myopia locus ever mapped, as responsible for a syndromic form of myopia characterized by extraordinarily high refractive errors (often > −15 diopters). Subsequently we demonstrated that sequence variants of the same genes are a factor influencing the development of juvenile onset myopia. Thus, opsin gene mutations and exposure to non-adaptive visual stimuli contribute to a malfunction of emmetropization causing common juvenile onset myopia. These finding suggest that genetic testing may be useful in identifying children who are at the greatest risk of becoming myopic before they manifest any refractive error. Moreover, early detection combined with the use of contact or spectacle lenses designed to balance the relative activity of the cones, thereby helping to restore normal visually guided eye growth, may be useful in slowing the progression of myopia in children.