Why does viewing the image formed at the near point cause some strain on the eye while no such strain is observed when the image is formed at infinity?

Asked by akankshyasahu | 29th Feb, 2012, 10:30: PM

Expert Answer:

When the eye is viewing an object at a far distance (such that parallel rays of light are entering the eye), the ciliary muscle within the ciliary body relaxes.  The ciliary processes pull on the suspensory ligaments (or zonules), which in turn pull on the lens capsule around its equator.  This causes the entire lens to flatten or to become less convex, enabling the lens to focus light from the far-away object.

Conversely, when the eye views an object at a near distance, an “accommodative demand” is created.  As a result, the ciliary muscle works or contracts, causing tension to be released on the suspensory ligaments and, subsequently, on the lens capsule.  This causes both (front and back) lens surfaces to become more convex and the eye to be able to focus at near. 

Answered by  | 1st Mar, 2012, 10:16: AM

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