A review and a suggested classification system for myopia on the basis of age-related prevalence and age of onset.

Systems for the classification of myopia are usually based on etiological dichotomies such as hereditary vs. environmental, physiological vs. pathological, structural vs. functional, or axial vs. refractive. The purpose of this paper is to propose a system for the classification of myopia based not on assumed etiological factors but on readily available and easily verifiable information, including age-related prevalence and age of onset. The proposed system classifies myopia into four categories: congenital, youth-onset, early adult-onset, and late adult-onset. Paradoxically, such a classification, being devoid of etiological assumptions, may help to make possible a better understanding of the etiology of the various categories of myopia.