Nearsightedness, also referred to as myopia, occurs when light rays entering the eye are focused in front of the retina instead of directly on it. 'Overpowered' eye requires laser correction to flatten the cornea and 'weaken' the eye optically, thus permitting clear distance vision.
Farsightedness, or hyperopia, occurs when light rays strike the retina before coming to a sharp focus; the focal point is said to be 'behind the retina'. The eye is 'underpowered' and requires laser correction to re-shape the cornea.
In the astigmatic eye, either the cornea or the lens is not equally curved; it is slightly oval in shape, resembling a rugby ball. Light rays entering the eye bend unequally, resulting in a distorted image. Laser treatment will change the shape of cornea, thus enabling light to come to a single point of focus on the retina.
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