Question

What is hypermetropia?How is it caused?​

Answer 1

Answer:

Hypermetropia (hyperopia, long-sightedness or far- sightedness) is a form of refractive error in which parallel rays of light coming from infinity are focused behind the light sensitive layer of the retina, when the eye is at rest.

• Donders (1864) discusses in his historical review about hypermetropia. Much of the problem was caused by confusion between the effects of presbyopia and hypermetropia on near vision.

• Small hypermetropia may be corrected by voluntary accommodation. Even high errors of refraction may be corrected this way, but convex glasses may be required if symptoms are not relieved.

• Emmetropia is the condition where the eye has no refractive error and requires no correction for distance vision. Refractive error (ametropia) results when cornea and lens inadequately focus the light rays, resulting in blurred images. The measuring unit for refractive error is dioptre (D), which is defined as the reciprocal of the focal length in meters.

• In hypermetropia, the cornea is flatter or the axial length is too short. Therefore, the images do not focus by the time they reach to the retina. For clear vision, a hypermetropic eye must accommodate to increase its lenticular power to bring distant objects in focus on retina. This requires contraction of ciliary muscle, and therefore, far-sighted eye is never at rest and work even harder to see near objects clearly. Hypermetropic corrections add positive focusing power to the eye for clear vision.

Answer 2

In an eye with hyperopia, light rays entering the eye focus behind the retina, rather than directly on it. Typically, this is because the eyeball of a farsighted person is shorter than normal.

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