Looking for a long amount of time at changing patter a ceitam color, or a deimin de of brightness also can affect what we "see." Staring at a certain color of a certain amount of brightness tires our eyes, and as a result, we may perceive things differently. In short, the tiring of our eyes following an excessive exposure to a certain kind of visual can cause optical illusions. These are called physiological optical illusions. An example of a physiological illusion is an "afterimage." Have you ever looked at a light and then the image of the light stayed in your eyes after you looked away? This optical illusion is mostly the result of the operation of the "cones" in one's eyes.