The term “power of accommodation” refers to the ability of the human eye to adjust its focus in order to clearly see objects at different distances. This adjustment is achieved by changing the shape of the eye’s natural lens.
The lens of the eye is flexible and elastic. When a person looks at objects that are close, the ciliary muscles surrounding the lens contract. This contraction causes the lens to become thicker and more convex, increasing its refractive power. As a result, the eye is able to focus on nearby objects. The power of accommodation tends to decrease with age, a condition known as presbyopia, making it more difficult to focus on close objects.

Ciliary muscles of eye are responsible for change in its focal length.