Why is normal eye not able to see clearly the objects placed closer than 25 cm ?

Explanation

A normal eye can see nearby objects because the ciliary muscles make the eye - lens more convex (or thick ) thereby increasing its converging power. This increased converging power of eye-lens can make a normal eye see objects clearly only when placed up to 25 cm from the eye. However, when objects are placed closer than 25cm, then the ciliary muscles cannot make the eye-lens more convex to increase its converging power further So as to focus them sharply on the retina. Due to this, such objects are not seen clearly. In other words, a normal eye is not able to see clearly the objects placed closer than 25cm because all its power of accommodation (or ability to increase converging power of eye - lens by making it more convex ) has already been exhausted .