Myopia (near-sightedness) is the most common refractive vision disorder in children. It is characterized by blurring of objects viewed at a distance, and is commonly the result of abnormal elongation of the eyeball – which causes the refractive image formed by the cornea and the lens to fall in front of the photoreceptors of the retina (Figure 1).
The underlying biological cause of myopia is unknown, and there is no widely accepted means of prevention or cure. The optical error of myopia can be corrected only by using spectacle or contact lenses or corneal surgery. If left untreated, moderate myopia is one of the leading causes of visual impairment worldwide. The greater the degree of myopia, the greater the risk of complications such as macular degeneration, retinal detachment, cataracts, and glaucoma (1); the risk is especially great when the negative refractive error is more negative than -6.00 D (diopters), a condition called ‘high myopia’. The prevalence of myopia varies greatly, depending on ethnicity, geographical location, and socioeconomic status, but is rising rapidly in most populations studied (2) (Figure 2). Myopia is a centuries-old problem, and although we have made great progress in scientific investigation of its underlying cause, we have been unsuccessful in preventing it from becoming named by the World Health Organization as an ever-increasing global health concern (3).
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