2.87

2.87 understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity

Rays of light from distant objects are almost parallel when they enter the eye. They require less bending. Muscles in the ciliary body relax and the lens is made thinner by the suspensory ligaments for focussing power.

Rays of light from near objects are already diverging when they enter the eye. They need much more powerful refraction to bend them to a focus on the retina. Ciliary muscles contract and the lens swells to a more rounded shape. This makes it more powerful and the rays are bent more to achieve a focussed image on the retina. 

In bright lights, the circular muscles contract and radial muscles relax, making the pupil smaller. The reverse happens in dim light.