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Explain presbyopia and astigmatism

Explain presbyopia and astigmatism?

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Presbyopia refers to the visual impairment where there occurs loss of cililary muscle strength hence, decreasing the capability of crystalline lens in order to adjust the images of nearby objects onto the retina. In presbyopia, the near point of the vision becomes more distant. The disease normally takes place in the old people. Astigmatism is caused due to irregular shape of refractive structures, specially the cornea. In astigmatism, a single object-point can generate more than one image onto the retina and therefore the vision becomes distorted.

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