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    Question

    Which one of the following lenses should be used to

    correct the defect of astigmatism?
    A Cylindrical lens Correct Answer Incorrect Answer
    B Concave lens Correct Answer Incorrect Answer
    C Convex lens Correct Answer Incorrect Answer
    D Bifocal lens Correct Answer Incorrect Answer

    Solution

    Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. This may be due to an irregular or toric curvature of the cornea or lens. The two types of astigmatism are regular and irregular. Irregular astigmatism is often caused by a corneal scar or scattering in the crystalline lens, and cannot be corrected by standard spectacle lenses, but can be corrected by contact lenses.

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