Not all snakes have heat pits and the snakes that do have them do not use them as a replacement for eyesight. The heat pits are a tool designed through evolution to locate and target potential prey with a better strike rate than eyesight and scent location. A lot of snakes have very good eyesight but the majority can't really focus in on anything at a distance of forty five centimetres or more. Althought a snakes eyes are very atoned to movement at far greater distanceOriginally Posted by Snakeman