What does "accommodation" mean in relation to the eye?

Accommodation refers to the ability of the eye's lens to change shape in order to focus on objects at different distances. The lens rounds to focus on nearer objects and flattens to focus on objects farther away from the eye.

This action is involuntary and occurs in mere milliseconds within healthy eyes, and the eye naturally increases its power of focus as an object nears it. The ability of the eye to accommodate often decreases as a person ages. This explains why people over the age of 40 begin to develop presbyopia, or the inability to focus on objects that are nearby, and need glasses to help focus while reading. Eventually, the ability to see farther away can also be affected.