Q. a. what are myopia and hypermetropia ? b.What are their causes? c.How van they be corrected?

Asked by Mrinal | 7th Mar, 2012, 06:40: PM

Expert Answer:

Myopia:
Myopia is that defect of human eye by virtue of which it can see clearly the objects lying at short distances from it. But the far off objects cannot be seen clearly by the myopic eye.
 
Causes:
1. increase in the length of the eyeball, as if distance of retina from the eye lens has increased.
2. decrease in focal length of the eye lens when the eye is fully relaxed. This is as if the ciliary muscles holding the eye lens do not relax fully and have some tension.
 
Correction:
One must wear spectacles with a concave lens of suitable focal length or power.
 
 
Hypermetropia:
It is that defect of human eye, by virtue of which it can see clearly the objects lying at large distances from it. But the nearby objects cannot be seen clearly.
 
Causes:
1. decrease in length of the eye ball, as if distance of retina from the eye lens has decreased.
2. increase in focal length of the eye lens, when the eye is fully relaxed.
 
Correction:
One has to wear spectacles with a convex lens of suitable focal length or power.

Answered by  | 8th Mar, 2012, 12:29: PM

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