Refractive vision disorders

Normal vision

Light rays converge at one point on the retina.

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Myopia - (nearsightedness or shortsightedness)

An abnormal disorder of the eye in which objects close to the eye produce clear images because parallel rays of light are brought to a focus before they reach the retina, but far away vision is blurry.

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Hyperopia (farsightedness)

An abnormal disorder of the eye in which distant objects produce images slightly more distinct then near ones because parallel rays of light reach the retina before they are focused. Both images are blurry, especially the near one.

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Astigmatism
Produced by structural or superficial defects of cornea or lens that makes blurriness or gives imperfect images. Light rays entering through the corona converge at many different points on the retina.

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Presbyopia
An eye condition occurring usually after age of 40s, in which only distant objects may be seen distinctly. The condition is caused because the lens inside the eye becomes less elastic and loses its ability to focus on close objects.