The Eye-Structural / Anatomical view
Considering the refractive states (only when it is a matter of Distance Vision) we can establish 4 groups,-
A) Normal Eye- Able to see all distance Objects clearly with out any extra efforts or strain on their eye.
Proper definition: The parallel rays of incident lights are creating a focus on Retina, when accommodation of the Eye is minimum.
so the picture / diagram will be,-
B) Eyes having refractive error-
The person who is able to see all near Objects clearly.
(We will not think about some one's inability)
Proper definition: All the parallel incident light rays are creating a focal point before retina
when accommodation of the eye is minimum.
And the diagram will be,-
2) Farsightedness: One can see the distance Objects clearly.
Proper definition: The parallel incident light rays are creating a focal point before retina when accommodation of the eye is minimum.
And the diagram will be,-
3) Astigmatism: One person can see neither the Distance Objects nor the Near Objects clearly.
Proper definition: Some of the parallel incident light rays are creating a focal point before retina & Some of the parallel incident light rays are creating a focal point after retina when accommodation of the eye is minimum.
And the diagram will be,-
4) Presbyopia: This condition is common among the age group of 40 and more then 40.
One person can not get clear vision while there are performing some near work although they don't have any refractive error for their distance vision.
Proper definition:
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