Refractive error Refraction is the bending of light as it passes through one object to another. Vision occurs when light rays are bent (refracted) as they pass through the cornea and the lens. The light is then focused on the retina. The retina converts the light-rays into messages that are sent through the optic nerve to the brain to the occipital lobe in the cerebral cortex. The brain interprets these messages into the images we see. Refractive errors occur when the shape of the eye prevents