When you look at an optical illusion, such as a curved line that is truly straight or a moving object that is static, you can believe that you are seeing things. You question whether your vision is deceiving you.

Not your eyes, I say. Because of how your brain and complete visual system receive and interpret an image, an illusion is evidence that you don't always see what you believe you do.
Visual illusions occur due to properties of the visual areas of the brain as they receive and process information. In other words, your perception of an illusion has less to do with the optics of your eye and more to do with how your brain processes information.