Briefly explain the following terms:
Power of accommodation
Topic: Power of accommodation
Answer
The POWER OF ACCOMMODATION is the ability of the EYE LENS to focus both near and distant objects clearly on the RETINA, by adjusting its own FOCAL LENGTH — that is, by changing its curvature.
THE MECHANISM, worth adding since the question says "explain": for a NEAR object the CILIARY MUSCLES CONTRACT, the suspensory ligaments slacken, and the lens becomes MORE CONVEX (thicker), bending light more strongly for a DISTANT object the muscles RELAX, the ligaments tighten, and the lens is pulled THINNER
DO NOT CONFUSE THIS WITH THE IRIS, which adjusts the size of the PUPIL and therefore how much LIGHT enters. The iris controls the AMOUNT of light; the ciliary muscles control the FOCUS.
It is the gradual LOSS of this power with age — as the lens hardens — that causes PRESBYOPIA.