What is an accommodation power of an eye? What is the least distance of distinct vision?

The ability of the eye lens to adjust its focal length as per requirement is called accommodation power of lens.

The ciliary muscles modify the curvature of the lens which in turn modifies the focal length of the eye lens. In the relaxed state of the ciliary muscles, the lens is thin and the focal length is more which enables us to see distant objects clearly. When the ciliary muscles contracts, the focal length decreases due to increased curvature of the lens and we are able to see near objects clearly.

The least distance of distinct vision for a young adult with normal vision is 25cm.