(FORTUNE Magazine) – WHEN WILLIAM STARK WAS 10 years old, a nail he was hammering in the cellar of his home in Pittsburgh shot upward and plunged directly into his left eye. His injury was bad enough that a surgeon eventually had to remove the lens. In an intact human eye, the lens filters out ultraviolet light, which can injure the eye over time. So when Stark's lens came out, UV light for the first time could make it all the way to his left retina. "I suddenly was seeing a whole bunch of the spectrum that I hadn't been able to see before," he recalls. A little like Superman, little William Stark had UV vision.

Ever since then, Stark's world has been painted according to a different plan. It's generally brighter and bluer. The sun appears more brilliant, the moon richer in off-whites. If he could find glasses that would help his left eye focus better, Stark suspects he would see flowers the way birds and bees do--rife with UV pigments that define alluring bull's-eye and landing-pad patterns. Although he says it's a coincidence, Stark's experience of hypersensory vision may have influenced his choice of occupation: He's a physiological psychologist at Washington University in St. Louis. In that capacity he investigates, among other things, ultraviolet vision in fruit flies.

Stark is not a total fluke. There has always been a minority of UV-seers among us. Like those with perfect pitch, color blindness, or abilities to smell aromas that others can't, UV-seers are reminders of how different the world can appear to two people standing next to each other.

Another UV-seer is Alan Bradley, a retired director of TV-based distance education at the University of Saskatchewan. He co-wrote the book Ms. Holmes of Baker Street, whose thesis is that Sir Arthur Conan Doyle's famous sleuth is actually a woman disguised as a man. Things are not always as they appear, says Bradley.

He discovered his own UV vision one spring day in 2003 while strolling in downtown Kelowna in British Columbia. During a recent cataract operation, his surgeon had implanted a plastic prosthetic lens in his left eye. When he arrived at a produce market, he was stunned by a brilliant mauve light. "It was almost as though I had been hit in the nose," he says. "It was like listening to a Mozart symphony in one ear in the key of C and in the other in the key of D," he says. "I had to look away."

He quickly determined the source of the dissonant radiance: a footlong black light that the market clerks used to check for counterfeit bills. His surgeon later told him that the particular lens he had implanted was unexpectedly allowing UV light to pass through. Anxious at first, Bradley found Stark, one of the few UV-seers with a web presence, and their correspondence put him at ease about his UV sensitivity. Now Bradley considers this ability an upgrade to his visual system. "I love it," he says.

One thing he loves about it is the way forests now sometimes look to him. In 2003 a fire scorched parts of nearby Okanagan Mountain Park. Last spring, as the vegetation started to recover, he was beguiled by what he saw. Regaling him were newly grown mosses in brilliant greens, sometimes with a metallic appearance, spectral enhancements due to UV light reflecting into his left eye. "It was absolutely unearthly and wonderful," he says, adding that he now routinely sees many more subtle gradations of blue and green.

The otherworldliness of UV vision made it to the big screen not long before it became part of Bradley's everyday experience. In the 2001 movie K-PAX, Kevin Spacey played a UV-seer in the character of "prot," who claims to be from the planet K-PAX. The film is based on the 1995 novel by Gene Brewer, who thought he was making up the UV-seeing trait "out of whole cloth." Says Brewer: "I needed something to raise the credibility of prot as an extraterrestrial being."

UV vision remains a rarity for terrestrial people, but it's commonplace in the animal world. The cobalt wings of Morpho butterflies reflect UV light into the compound eyes of their fellow flutterers. Some birds of prey can track rodent movement via UV emissions from the rodents' urine. Bees see flowers in a UV-extended rainbow. Fish quite likely rely on UV sensitivity to locate otherwise transparent plankton.

Then there are human animals like Stark and Bradley. As a vision researcher, Stark was able to apply the tools of his research specialty to examine some details of his own UV-sensitive eye. He found that he could detect wavelengths down to some 305 nanometers, which is about the shortest UV wavelength of sunlight that the atmosphere's ozone layer allows through. Normal vision ranges between 400 and 700 nanometers, a tiny slither of the electromagnetic spectrum that corresponds to the colors of the visible rainbow.

Stark and Bradley may be standouts in standard FORTUNE-reading countries, but there almost certainly are multitudes of UV-seeing people in developing countries where cataract surgery is less apt to include an intraocular implant, says Dr. James Aquavella, an eye surgeon and professor of ophthalmology at the University of Rochester Eye Institute. The condition of not having a lens in your eye, like Stark's, is known as aphakia, and Aquavella notes that there probably are many thousands of UV-seeing aphakics walking around places like India right now.

There also used to be more aphakics in the past because there were no lens implants available. One of the more famous aphakics was the impressionist master Claude Monet, who had cataract surgery on his right eye in 1923 at the age of 82. Art historians have long noted that Monet's palette changed after his surgery. Despite being fitted with spectacles designed to compensate for his lost lens, Monet never was happy with the result, complaining that the colors he saw were exaggerated and "quite terrifying." Bradley can relate. ■

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