Mr IP, you have my sympathies for your nearsightedness, sore joints, and tinnitus. (Mine come from genes, arthritis, and friends in rock bands, respectively.) But I especially share your enthusiasm for widened color perception! I've read of some tetrachromatic women in Denmark and seen some colorful canvases by a tetrachromatic painter trying to convey her vision of the world, but -- alas -- it would take some serious genetic engineering to allow a man to see four primary colors. (Conceivably we could train ourselves to distinguish extra colors with notch-filtered lenses, perhaps a different one on each eye, but I'm sure it wouldn't be the same.) How was Mrs IP's gift discovered? I recall reading that some tetrachromats were unaware until they were tested.