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Defect of vision
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Cause
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Corrective Measure
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Myopia
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Lengthening of eye ball from front to back or the lens is too curved.
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Using suitable concave lens.
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Hyperopia
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Shortening of eye ball from front to back or the lens is too flat.
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Using suitable convex lens.
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Astigmatism
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Uneven curvature of the cornea.
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Using suitable cylindrical lenses.
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Presbyopia
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Loss of flexibility of lens.
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Using suitable convex lens.
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Cataract
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Lens turning opaque
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Surgery or use of convex lens or implantation of plastic lens.
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Colour Blindness
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Genetic defect
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No control measure
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Squint
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Formation of cross-eye
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Surgery and suitable exercise.
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