Refraction is a natural effect that alters the image of an object when viewed through a transparent medium (glass, water). If we give it a thought, Refraction is very important in the way we perceive the world, because practically all our visual stimuli are the result of Refraction. Between an object, a landscape or a person and our eyes there is always the atmosphere. And in fact, depending on its temperature, the Refraction is also different. Then the vitreous of our eyeballs intervenes. Which can have a different consistency and density from person to person. What would be the image we would have of the world had not the Refraction intervened?