Myopia, or short-sightedness, is a condition in which near objects are seen more clearly than objects which are far away.
The main symptom is blurred distance vision. Short-sighted people often report difficulty distinguishing details on road signs and scoreboards.
Another common symptom is squinting the lids together in an attempt to see clearer. This works by narrowing the aperture they are looking through and therefore reducing the size of the blur circle on the retina inside the eye.
Myopia tends to first develop during adolescence as the eye grows to full adult size. Myopia occurs either due to hereditary factors or due to environmental stress and a subsequent spasm of the eye focusing muscles.
Myopia is corrected with either contact lenses or spectacles. Since these lenses are thickest at the edge, new spectacle lens technologies have been developed to produce thinner and lighter lenses.