Why don’t most humans see UV? It might be the cost of having sharp eyesight. When light passes through our lenses, shorter wavelengths are bent at sharper angles. Even if the lens admitted UV, it would focus these wavelengths at a point well in front of the others, blurring the image on the retina. This is called chromatic aberration. It’s less of an issue for small eyes, or for those that don’t need to be very acute. But for big-eyed animals with sharp vision, it’s a problem.
