Astigmatism is a malformation or imperfection, congenital or accidental, of the globe of the eye, in consequence of which the individual does not see objects clear and distinct, but with a blurred outline. It is due to the cornea or transparent outer coat of the eye not being regularly spherical, but having different degrees of curvature in different directions. Usually the degree of convexity is not the same horizontally as it is vertically, so that the rays from an object, instead of converging into one focus, meet in more than one. If a person with this defect is looking at vertical lines crossed by horizontal ones he will see the one set more distinctly than the other, though a slight movement will enable him to see the other distinctly also, but not at the same time. Almost all eyes are more or less astigmatic, but persons only become aware of it when it is excessive. Special lenses are required to correct it - usually lenses plane in one direction, and concave or convex in the other. Short-sight or long-sight is often associated with astigmatism, so that the necessary spectacles may not be very easily provided. Research Astigmatism
Abbreviations
Medicine
Research Astigmatism