Myopia is a visual defect in which distant objects appear blurred because their images are focused in front of the retina (the light-sensitive layer at the back of the eye). So-called simple myopia, or near-sightedness ("short-sightedness" in the UK), is due to the eyeball being slightly longer, or the cornea (the front part of the eye) being slightly steeper, than normal. It can be easily corrected by using diverging spectacle lenses or contact lenses to move the image back to the retina or through the surgical procedure known as LASIK (laser in situ keratomileusis).

Simple myopia tends to run in families and may develop rapidly or slowly, often gradually getting worse during childhood and adolescence. It affects boys and girls equally, often stabilizing during young adulthood.