Accommodation reflex

The Accommodation Reflex is a reflex action of the eye, in response to focusing on a near object, then looking at distant object (and vice versa).

A near object (for example, a computer screen) appears large in your field of vision , and the eye receives light from wide angles. When you focus on a near object, the pupil constricts in order to prevent diverging light rays from hitting the periphery of the retina and resulting in a blurred image. As the pupil constricts, the lens becomes more spherical to allow for the diverging light rays.

When you look at a distant object, parallel light rays enter the eye, and the pupil dilates. Muscles in the eye flatten the lens.