Structural defects of the eye in which the light rays from a viewed object do not meet in a single focal point, resulting in blurred images being sent to the brain. An astigmatic cornea is not perfectly rounded like a basketball but has an irregular shape more like the side of a football. Astigmatism is most often combined with myopia or hyperopia . A difference in the focal point of the eye in one meridian from another (eg between the horizontal and vertical planes). It can usually be corrected with a cylindrical (toric) lens. An irregularity in the curvature of the cornea, resulting in unequal blur in the two principle meridians. A Refractive Error of the eye in which refractive power is not uniform in all directions (meridians). Light rays entering the eye are refracted unequally through different meridians, which prevents formation of a sharp image focus on the retina. Correctable with a cylindrical lens.

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