In normal vision, light enters the eye and is focused by the lens on the retina. The retina transforms the images into electrical impulses which are transmitted to the brain by the optic nerve. If the lens does not focus properly, vision will be distorted. The lens continually changes shape to focus objects which are various distances from the eye. The shape of the lens is controlled by the zonules, thin muscle fibers which hold the lens in place. The zonules contract and relax to control the size and
shape of the lens. When we look at something close up, the zonules relax, allowing the lens to become fatter. When we gaze into the distance, the zonules contract and cause the lens to become thinner.