"While the language may be lovely and the reasoning just, the ideas themselves may prove trivial." -Lu Chi (from Wen Fu)

Writing Prizes:
Winning Essays

Three Generations Prize for Writing in the Sciences

"Seeing Is Believing"
Anna Raphael '01

Prior to the development of the laser used in Lasik, doctors attempted to reshape the cornea manually. Only one of these techniques, radial keratonomy (RK), was considered successful in treating nearsightedness. RK was developed in the seventies in the former Soviet Union. Four to eight tiny slits are cut in a spoke-like pattern into the cornea. This has the effect of slightly collapsing and flattening it. RK is similar to Lasik in that it is not painful and had a quick recovery period. Yet the incisions must penetrate 90-95% through the cornea, leaving it permanently weakened. RK is also effective only for mild nearsightedness.

Even earlier than RK, there was the rather crude process by which the corneal flap was cut from the eye with a microkeratome, frozen, then carved to the desired shape and thickness before being sutured to the eye again. The cornea often became warped as a result, making vision worse from severe astigmatism.

The technology needed for Lasik was not realized until the early eighties, when an engineer named Srinivasan noted that an argon fluoride laser could remove extremely thin layers from plastics without heat damage. Plastics don't absorb UV light as well as visible or infrared light, but the laser's UV beam was so loaded with energy that it vaporized the microscopic layer of plastic that it was able to penetrate. The laser didn't partially melt the material beneath the vaporized layer; ¡t was "cool." This made it perfect for electronics work such as etching computer chips and circuits.

Lasik is just PRK done underground. Instead of removing the sensitive cells at the cornea's surface, a 160-micron flap is sliced away, peeled back and the exposed tissue reshaped. One surgeon likens it to opening the cover of a phone book 500 pages thick, "removing 180 pages, 25 or 30 pages at a time, then putting the cover back." (Remember that the cover of the corneal "phone book" should really be a third of its own thickness.) In any case, keeping the "cover" intact spares the patient a lot of pain and the risk that the cells could grow back cloudy or deformed.

Yet creation of the flap brings its own problems. The flap can become detached, warped, wrinkled. Oily deposits can become trapped underneath or the wrong kind of cells can grow under the flap. Total blindness is extremely rare-estimated odds are less than 1 in 10,000, but approximately 2-3% of patients suffer serious damage to their vision, ranging from seeing severe halos to multiple images. An FDA clinical trial on 1013 eyes showed that 3.5% saw halos around lights, 3 % had worse vision than with glasses and 1.7% suffered severe glare. Additional surgery cannot aIways correct these problems; sometimes it worsens them. The complication rate goes up with more inexperienced surgeons, generally defined as those having done fewer than several hundred procedures.

The "cool" laser works when excited argon and fluorine molecules emit UV light of a wavelength exactly 193 nanometers. The energy contained in the 193-nanometer light is just the amount needed to break the bonds within the protein that makes up our corneas. A researcher first noted in Health Physics that the laser produced a small indentation or "dimple" in the surface of a rabbit cornea, which he initially ascribed to dehydration. In early clinical studies, more animal corneas treated with the laser were examined under the electron microscope. Time and again, the pictures show normal cells standing or stretching in their neat rows, then suddenly nothing where the laser has struck. We have often heard of the deft tornado that razes one house but leaves the one across the street untouched. The laser acts like this tornado, except it leaves no debris. A tornado acting like this laser would simply make a house vanish.

At first, doctors were eager to use the laser in place of the scalpel for RK. But laser RK didn't work. You couldn't zap slits into the cornea-you'd leave holes instead. With such an effective tool for removing tissue, the obvious next step was to directly carve the surface of the cornea. This was the basis for photorefractive keratonectomy (PRK), Lasik's nearly identical predecessor.

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• Lynne Viti and Wini Wood
• Wellesley College Writing Program
• Created by: Nora Jarrah '02 & Jerina Hajno '04
• Date Created: August 8, 2001
• Last Modified: August 4, 2008
• Expires:July 31, 2009

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Photograph of typewriter © Ria Davidis 2000