Male Speaker: We see when light from an object enters our eyes and falls on the retina where sensitive cells are stimulated sending messages along the optic nerve to the brain. Focusing is controlled by the lens and the ciliary muscles and ligaments which surround it to focus on something close-up the muscle contracts relaxing the tension in the ligaments which pull less strongly on the lens. The lens bring to a round shape to focus on something far away the muscle relaxes and the lens becomes flatter. The amount of light entering the eye is regulated by the muscles in the iris. These make the pupil larger or smaller letting more or less light in.