Question

The change in focal length of an eye lens is caused by action of what

Answer 1

Answer:

The ciliary muscle is a circular muscle that relaxes or tightens the zonules to enable the lens to change shape for focusing. The zonules are fibers that hold the lens suspended in position and enable it to change shape during accommodation. It increases or decreases the focal length of the eye lens.

Therefore it is caused by ciliary muscles

Explanation: