Epidemiology and Pathogenesis of Myopia

Myopia is a common refractive condition in children and teenagers globally, and is considered as a public health issue of twenty-first century. It was predicted that half of the world’s population (nearly five billion) will become myopic by the year 2050. The prevalence of myopia and its progression rate varies with age, geographical location and ethnicity. The development of myopia is generally irreversible with the majority of cases being associated with excessive elongation of the eye. It has a complex multi-factorial aetiology which includes both genetics and environmental risk factors. The mechanical stretching and thinning of retina, choroid, and sclera over time contribute to the development of pathologic myopia. Various theories and ocular expansion models are proposed to be linked with pathogenesis of myopia. This chapter summarizes the prevalence and progression trends for myopia, and the mechanisms that are believed to be associated with myopiagenesis.