Myopia or nearsightedness is corrected with contact lenses, spectacles or laser surgery through optical repositioning of the image of a distant object to a point closer to the eye. This type of vision imperfection is generally caused by combined corneal/crystalline lens refraction that is too strong in relation to the length of the eye. Light is thus focused at a point in front of the retinal fovea, resulting in blurred vision. In many cases a nearsighted person is capable of seeing clearly without correction when viewing objects relatively close to the eye.
There are a variety of reasons why a person may develop myopia: congenital, environmental, physiological, or some combination of these factors can all play a role in the development of nearsightedness. Some studies indicate that excessive "near vision work" such as prolonged periods of computer use or reading from school age and through teenage years can cause a physiological condition called accommodative cramp with resultant nearsightedness. Other researchers have observed a link between nearsightedness and proximity to urban areas in children.