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Advances in laser-vision correction provide visual results that often surpass 20/20.
Special to Ophthalmology Times®
I found myself fascinated by a 1983 paper by Steve Trokel, MD, in the American Journal of Ophthalmology, in which he used an industrial excimer laser to make patterns in cadaver animal eyes. I had done some research with Trokel while I was in medical school at Columbia University College of Physicians and Surgeons in New York, New York.
I contacted Trokel and told him that I would love to be involved. I knew that there were very limited facilities at Columbia for animal research; at Louisiana State University (LSU), I had access to a large vivarium, the Delta Primate Center in Covington, Louisiana.
It was owned and operated by Tulane University; LSU used it as well. So in 1984, Charles Munnerlyn, PhD, Trokel, and I began working together to develop laser-vision correction. Steve Klyce, PhD, a professor of ophthalmology at LSU, soon joined the team and became an important member.
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So begins the journey
Munnerlyn brought an industrial excimer laser to the lab, and we ablated thousands of plastic test blocks before moving on to cadaver animal and human eyes.
As we progressed, we performed the procedure on living rabbit and monkey eyes. Through our years of work we were able to refine the hardware, software, surgical technique, and perioperative regimen.
There was a point when the rabbits were developing such extremely elevated, thick anterior corneal scars that the project seemed doomed.
In one week, I lost my research coordinator and my technician. They gave the same reason for quitting: the excimer project was too depressing for them to continue to come to work every day.
The hyperplastic scars decreased dramatically, however, when we increased the number of steps in our closing diaphragm (there were no flying spots yet, no trackers).
When we had 5 steps in the ablation sequence, I would shoot for a few seconds, then hand-crank the diaphragm to its next position, then shoot again, and repeat. When we increased the number of steps to 40 and automated the process, it made a big difference in outcomes.
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So progress was challenging for our team, but an unexpected opportunity arose in 1988. Alberta Cassady was a 62-year-old woman with cancer of the orbit, requiring exenteration; this would, of course, require the removal of the globe, the eyelids, and the contents of the orbit.
She would be left with a large, deep, skin-lined socket. With a massively disfiguring procedure looming, and a poor prognosis even with the surgery, Cassady bravely offered to let our team perform experimental surgery on her eye. We did not ask Cassady to do this; she volunteered, which stunned us.
Because her cancer surgery was looming, time was of the essence. After receiving emergency permission from the Food & Drug Administration (FDA), we rushed Cassady past the monkey cages, and on March 25, 1988, I had the honor of performing the world’s first laser-vision correction procedure, PRK, in the eye of a living human subject at the Delta Primate Center.
The research team watched her heal on a daily basis, right up until exenteration 11 days later. The refractive outcome was right on target, and the pathology report showed the early healing pattern that we now know so well.
Sadly, Cassady lost her battle to cancer. Her bravery and generosity in the face of such tragedy provided vital information that allowed the FDA to accelerate the approval process.
Even though it is usually only wealthy donors who have facilities named after them, our team demanded that LSU allow them to name our laser facility after such a brave and selfless woman.
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The FDA was so impressed by the daily postoperative evaluations, the refractive outcome, and the histological specimen that they allowed the team to start the blind eye human trials immediately, rather than more months and years of monkey trials.
Laser-vision correction has come far, but it all started with the selfless act of one brave woman. Looking back on the procedure we performed on Cassady so many years ago, I am so proud and excited to see how far laser vision correction has come.
With LSU’s permission, we brought the excimer laser across Lake Pontchartrain from Covington to New Orleans to start the blind eye study. LSU was afraid that the argon fluorine gas would leak from the laser and kill everyone, however, so they placed the laser in a trailer outside the main building. Our team was very disappointed, and a bit embarrassed, to march patients into a trailer.
It turned out to be a blessing in disguise, because we were located 5 feet from the university’s trash compactor. When the compactor was in operation, our trailer shook very gently, giving us much smoother ablations than we deserved to get (no flying spots or trackers yet, remember).
All the patients did well, but those who were treated on the days that the compactor was working did even better. So, we figured it out: smoother ablations are better.
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Without trackers, we were forced to try some creative ways to stabilize the eyes. We first had a steel column—with 20 curved teeth at the end—that dropped down out of the laser and was screwed into the limbus.
This draconian method worked, but we were afraid that a frightened patient might jump off the gurney and leave their eye behind, tethered to the laser.
Next we tried a suction ring with 4 fluid-filled chambers around the annulus. Each had a tiny bubble of air, so they were, in effect, 4 carpenters’ levels. As I fired the laser, Klyce would move my hand into a position where all 4 carpenters’ levels indicated that I was parallel to the floor.
We added retrobulbar injections, and on rare occasion, lateral canthotomies, to be sure that we had enough room for the large 4-chamber suction ring. Eventually, flying spot lasers with trackers were introduced, as well as other refinements.
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The rest is history
Since that first PRK procedure was performed in 1988, our original team has contributed to, and still contributes to, significant advances in laser-vision correction.
Of course, PRK has evolved dramatically and is popular all over the world, including the US; in some countries, it is the most popular form of laser-vision correction. The latest iteration of PRK, epi-Bowman’s keratectomy (EBK), is the best yet with postoperative comfort and speed of return of vision that is competitive with LASIK.
The most prevalent type of laser-vision correction, however, is LASIK, which was introduced a decade after PRK by Ioannis Pallikaris, MD, of Greece; it is one of the most commonly performed elective surgeries, with more than 28 million procedures performed worldwide.
Now, LASIK is commonly performed using all-laser femtosecond technology. When combined with advanced wavefront, topographic, or customized technology, laser-vision correction—both LASIK and PRK—can provide visual results that often surpass 20/20.
About the author
Marguerite B. McDonald, MD, FACS
McDonald is clinical professor of ophthalmology at both NYU Langone Medical Center, New York, New York and Tulane University Health Sciences Center, New Orleans, Louisiana, and in practice with OCLI Vision, Oceanside, New York. McDonald is a consultant for Johnson & Johnson Vision and ORCA Surgical.