The Origin of “Excimer”
The name “excimer laser” is derived from the terms “excited” and “dimers,” molecules composed of two atoms that only bind together in an excited electronic state.
A modern medical breakthrough that has touched millions of people started with some turkey left over from Thanksgiving Day dinner, November 26, 1981.
Three researchers at the IBM ® Thomas J. Watson Research Center in Yorktown, New York—Samuel Blum, Rangaswamy Srinivasan and James J. Wynne—had been exploring new ways to use the excimer laser that had been recently acquired by their laser physics and chemistry group. Blum was an expert in materials science; Srinivasan was a photochemist with 21 US patents to his name; and Wynne was a physicist, who was the manager of the group at IBM.
The excimer laser uses reactive gases, such as chlorine and fluorine, mixed with inert gases, such as argon, krypton and xenon. When electrically excited, the gas mixture emits energetic pulses of ultraviolet light, which can make very precise, minute changes to irradiated material, such as polymers.
“We wondered if the excimer laser could so cleanly etch polymeric material, what would happen if we tried it on human or animal tissue?” remembers Wynne. “What really broke things open, after all the talk of what kind of tissue we would use, was that Sri brought his Thanksgiving turkey leftovers into the lab the day after Thanksgiving in 1981,” said Wynne. “He used the excimer laser at 193nm to etch a pattern in whatever bone, cartilage or meat was on the tissue sample … I had this moment of eureka, we have a new form of surgery! By using the ultraviolet light of the excimer laser, we were getting an extremely clean cut, with no evidence of damage to the surrounding tissue.”
Instead of burning living matter, each laser pulse disrupted the molecular bonds in a very thin layer on the surface of the tissue, effectively disintegrating it, leaving no observable collateral damage to the underlying or adjacent tissue. To demonstrate this effect to the medical technology field in a dramatic way, the team produced a highly magnified electron micrographic image of a highly magnified single human hair, etched by the laser. This image was published around the world.
Srinivasan, Blum and Wynne had many exploratory discussions about how this “clean excision” could be used for brain surgery, dentistry, orthopedics and dermatology.
At the time, eye surgeons were searching for an alternative to using “cold steel” or a scalpel for the surgery procedure used to correct nearsightedness. A scalpel was not very precise, could leave the cornea permanently weakened and required a long recovery time.
Upon learning of the IBM work, ophthalmologist Stephen Trokel, affiliated with Columbia Presbyterian Medical Center in New York City, came to the Watson Research Center in the summer of 1983 to collaborate on experiments with Srinivasan and researcher Bodil Braren. Trokel, Srinivasan, and Braren wrote a paper introducing the idea of using the laser to reshape or sculpt the cornea (the clear covering on the front of the eye) in order to correct refractive errors, such as myopia or hyperopia. Their paper, published in a major ophthalmology journal in December 1983, launched a worldwide program of research to develop excimer laser-based refractive surgery. Years of experimentation and clinical trials followed. In 1995, the US Food and Drug Administration approved the first commercial excimer laser-based refractive surgery system, almost 14 years after the team’s initial experimentation.
Today LASIK (laser-assisted in-situ keratomileusis) eye surgery is the most popular vision correction surgery performed worldwide, due to its rapid healing cycle and minimal pain. The procedure permanently changes the shape of the cornea in order to improve vision and reduce or potentially eliminate nearsightedness, farsightedness and astigmatism. Millions around the world have had the procedure, and more than 90 percent of patients achieve 20/20 to 20/40 vision and are able to perform all or most of their daily activities without glasses or contact lenses. Modern improvements to the procedure enable many patients to achieve 20/15, and even 20/10, “superhuman” vision, something not achievable with eyeglasses or contact lenses.