near-sightedness (myopia): the refractive power of the eye is too strong in proportion to the length of the eyeball; the focus lies in front of the retina.
far-sightedness (hypermetropia): the refractive power of the eye is too poor in proportion to the length of the eyeball; the focus lies behind the retina.
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astigmatism: the cornea has no spherical surface; no focus can be produced on the retina.
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Near-sightedness – the eye is too long for the refractive power of the optic system
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Far-sightedness – the eye is too short for the refractive power of the optic system
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