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Visual deficiencies-Myopia and hypermetropia

How visual deficiencies termed as myopia and hypermetropia can be optically described?

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Myopia is the visual situation in which the images are made before (or in front of) the retina. Hypermetropia is the visual situation in which the point of image made is beyond (or behind) the retina. In reality myopia is due to a raise in the distance between the retina and crystalline lens, mostly caused by a slight flattening of the eyeball. In hypermetropia, the retina is very close to the crystalline lens due to slight shortening of eyeball. In myopia the near point and far point of vision come closer (that is, the refractivity of crystalline lens which corresponds to the maximum distension capacity of ciliary muscles is not sufficient to give visual accommodation). In hypermetropia, the ciliary muscles are not capable to contract more to compensate the insufficient position of the retina, that is, the near point becomes more far-away.

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