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About the Excimer Laser

A modern medical breakthrough, that touched millions of people, started with some turkey leftover from Thanksgiving Day dinner on November 26, 1981.

In 1980, IBM began to study the use of the excimer laser to etch polymeric materials used in packaging of silicon microchips during the manufacturing process. Three IBM researchers explored its use on various types of live tissue and made the discovery that inspired the development of LASIK eye surgery. With the Excimer laser, ophthalmologists can remove very small amounts of corneal tissue, equal to approximately 1/200th of the thickness of a human hair, in about 2 billionths of a second. This procedure completely transformed the way doctors surgically treat common vision problems and is the reason that over 20-million people today do not need glasses or contact lenses.

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 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 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. 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."

Here, the excimer laser was used to demonstrate precision and scale, etching

Here, the excimer laser was used to demonstrate precision and scale, etching "IBM" onto a strand of human hair

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 single human hair, etched by the laser. This image was published around the world (See picture on the left).

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 a scalpel for the surgery procedure 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 work at IBM, ophthalmologist Stephen Trokel, affiliated with Columbia Presbyterian Medical Center in New York City, came to the Watson Research Center in 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 'window' on the front of the eye) 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 experiments.

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 to improve vision and reduce or potentially eliminate nearsightedness, farsightedness and astigmatism. Millions of people around the world have had the procedure and more than 90 percent of them achieved 20/20 to 20/40 vision and were 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.

The excimer laser, linked to a computer, is so accurate that it removes tissue at a rate of less than 0.25 microns per laser pulse (one micron = 1/1000th of a millimeter). It can remove corneal tissue in a controlled manner, not possible with conventional ocular microsurgery.

To correct refractive errors, such as myopia, hyperopia and astigmatism, the laser cleaves individual molecular bonds to remove corneal tissue, which enable light rays to come into sharp focus onto the retina. Computer programs control the surface sculpting of the cornea to ensure the highest possible accuracy and success of the intended refractive change. It not only changes the refractive power of eyes, but also the lifestyle of patients who previously had to wear contact lenses or glasses to correct the symptoms of their underlying refractive error.