Question

Answer the following briefly:
What is meant by ‘Power of accommodation’ of the eye? Name the part of the eye responsible for the same.

Answer 1

Hint: To answer this question we should know what about the power of the eye. We can relate power with the focal length of the eye. To solve the next part of the question, we should study the role of different parts of the eyes while focusing for any object in near and far condition. The part with the maximum role will be our answer.

Formula used:
Power = 1/focal length

Complete step by step answer:
Power of Accommodation:
The power of accommodation of an eye is its reflex to change itself because of focusing in on a close to protest and afterward abruptly focusing in on a distant article. It essentially includes the focal point and the Ciliary muscles

Explanation:
When viewing objects which are nearby, the ciliary muscles contract, the lens becomes thicker. It is squeezed into a more convex shape and the focal length decreases hence the curvature increases. The images again fall on the Retina. Here the eye is “accommodating” by taking shape (thicker) so that the image falls on the Retina.

When viewing objects are away, the ciliary muscles expand, the lens becomes thinner. It is relaxed/loosened into a less convex shape and the focal length increases (curvature decreases). The image again falls on the retina. Here the eye is ‘accommodating’ by taking a slimmer shape as the image falls on the Retina.

However, the focal length of the Eye cannot be minimized below a certain minimum limit. When we read a book very close to your eye i.e. closer than $25cm$ , the book will appear blurred. This is because the minimum distance at which our eye can see an object most distinctly without strain is $25cm$ . This is called the “Least distance of Distinct Vision” or “Near point of the eye”. The farthest point up to which the eye can see objects is called the “Far point of the eye”. For a normal eye, it is infinity.

Hence, Ciliary Muscles are responsible for power of accommodation in the eyes.

Notes: Ciliary muscle control the focusing of the eye lens and can change the thickness and curvature of the lens. This process of focusing is called accommodation. The accommodation of an eye is its reflex to change itself. When the ciliary muscle is relaxed, the crystalline lens becomes flat, making the focusing power minimum.