The Quest for Perfect Vision

David L. Shenkenberg, Features Editor

The public hearing of the FDA Ophthalmic Devices Panel on April 25, 2008, gave industry observers insight into the safety and efficacy of lasik (laser-assisted in situ keratomileusis) after more than a decade of its use on patients.

The purpose of the meeting varied according to the person being asked. Lasik surgeons and other members of the industry presented data showing that the overwhelming majority of patients are satisfied after the procedure and experience a greatly improved quality of life, whereas a few dissatisfied patients and their advocates voiced concerns.

Although this meeting focused on patient satisfaction with the procedure, the FDA regulates the medical devices themselves — in this case, the lasers used during lasik. Donna Bea Tillman, director of the office of device evaluation in the FDA’s Center for Devices and Radiological Health, said, “The whole purpose of this meeting today is for us to attain some additional information from the public and to have a discussion among the panel members about some important issues relating to lasik ...”

Before the procedure, patients receive anesthetic eye drops. An eyelid speculum holds the eyelids open during the procedure.

Although femtosecond and excimer lasers for lasik seem to get all of the attention, much of the improvements in lasik technology have been in scanning and tracking methods. This wavefront scanner measures the unique imperfections in each patient’s eye, enabling ophthalmologists to customize lasik to each patient.

Lasik involves just two quick steps. A suction ring stabilizes the eye during the first step, during which the ophthalmologist uses a sharp blade or femtosecond laser to cut a flap in the cornea — the thin and clear outer covering of the eye. Second, the ophthalmologist uses an excimer laser underneath the flap to reshape the inner layers of the cornea so that patients can see better, ideally 20/20 without glasses or contact lenses.

Hearing both sides

At the hearing, Dr. Kerry Solomon, a lasik surgeon at the Storm Eye Institute at the Medical University of South Carolina in Charleston, presented a comprehensive analysis of patient satisfaction. His staff reviewed almost 3000 lasik studies from around the world — 10 years of data. The conclusion: more than 95 percent of patients who had undergone the procedure were satisfied with the outcome.

More than 95 percent of lasik patients report satisfaction with the procedure, yet a vocal minority has called for a moratorium. During lasik, the excimer laser beam comes from the arm of a workstation as the patient, lying on her back, looks up.

Solomon, a very satisfied former lasik patient himself, told the panel, “Of note, nearly 30 percent of lasik surgeons themselves have elected to undergo lasik, nearly five times more than the rate of the population at large.”

On the other hand, the dissatisfied patients and their advocates stated that satisfaction and quality-of-life surveys are subjective and de-emphasize the risk of complications. “The lasik industry wants the public to believe that a high satisfaction rate indicates a low complication rate,” said Matt Kotsovolos, a dissatisfied patient and the former chief financial officer of the Duke Eye Center at Duke University Medical Center in Durham, N.C.

This image shows what lasik patients see when they look up at the arm of the workstation during lasik. Patients are told to focus on the red light for about 60 s while the excimer laser beam reshapes the cornea with ultraviolet radiation, which is invisible.

The American Society of Cataract and Refractive Surgery estimates that about 2 to 3 percent of patients have complications. Some lasik practitioners say less than 1 percent. More than a million patients have the procedure each year.

Several of the dissatisfied patients said that they had felt depressed after experiencing complications of lasik and questioned the ability of lasik surgeons who have financial conflicts of interest to objectively review the procedure. Lasik surgeons say that the mental state of depressed patients before the procedure is unknown and that no published studies have linked lasik to depression. Dr. Roger Davis, a clinical psychologist, asked the panel to declare a moratorium on the excimer laser used for lasik until quality-of-life studies are performed exclusively with patients who have complications.

A femtosecond laser system is used to create the lasik flap. During flap creation, the patient is on his back looking up at the silver-colored metal cone, which is below the upper-right monitor and the black knob. The femtosecond laser light comes from an opening at the tip of the cone. It shoots out infrared light, which also is invisible.

The most common complication of the procedure is dry eye, the severity of which can range from discomfort to a long-term inability to produce tears due to severing of certain nerves in the cornea. Lasik surgeons say that about the same percentage of patients complain of dry eye before the procedure. Even rarer complications include starbursts, halos, glare and night-vision problems.

Perhaps the most convincing evidence in favor of the procedure came from the armed forces. Cmdr. David J. Tanzer, M.D., director of the Refractive Surgery Center at the Naval Medical Center San Diego, said that he has flown with pilots who have undergone successful refractive surgery, trusting his life in their hands. “If I did not personally believe that laser vision correction was in their best interest, I would not be treating anybody on active duty, let alone an aviator,” he said. NASA has approved lasik for astronauts as well.

The chairperson of the FDA panel, Dr. Jayne S. Weiss of Kresge Eye Institute of Wayne State University in Detroit, pointed out that, although accounts of a few dissatisfied patients are compelling, the panel also needs to look at the experiences of the majority of lasik patients.

Weiss said she believes that lasik is safe and effective. However, she expressed concerns about “aggressive marketing” and about how the procedure is treated as a “commodity” in economic terms rather than as a surgical procedure with risks, even though the risk may affect only a small percentage. The panel, which consisted mostly of ophthalmologists, focused on ensuring that patients have proper informed consent and that only good candidates for the procedure are selected.

Although insurance companies drive down the costs of most medical and surgical procedures, lasik is an elective surgery and therefore is not covered by insurance, so lasik surgeons can charge what the market will bear – $2000 on average per eye. Even though lasik surgeons can become wealthy from the procedure, competition is fierce, which creates a need for advertising.

Dr. Karl G. Stonecipher, medical director at TLC Greensboro and co-medical Director at TLC Raleigh, both in North Carolina, regularly performs lasik, and he has conducted numerous clinical trials of the procedure for the FDA and has been a lasik patient himself.

Stonecipher told Biophotonics International that the public hearing was a response to high-ranking officials who had bad outcomes. “The public outcry is there, but there is in fact a minority of patients who have problems.” He pointed out that all medical and surgical procedures carry some degree of risk and said, “I beg you to find a procedure that has a better track record than lasik.”

A number of factors can influence patient outcome, such as the skill and experience of the surgeon, the equipment used, the patient’s compliance with postoperative guidelines, the patient’s age and health before the procedure, and the selection process for good candidates.

Dr. Steven C. Schallhorn, who founded the US Navy’s refractive surgery program, has been influential in the public’s acceptance of lasik. One year ago, he retired from the Navy and entered into private practice with Optical Express in San Diego. Schallhorn also has conducted numerous studies for the US Department of Defense. Before these studies, soldiers were disqualified from becoming pilots if they were not born with perfect vision. As a direct result of his research, pilots who have undergone successful refractive surgery can fly planes.

Schallhorn said, “I think that lasik is safe and effective, and that has been proven in numerous clinical trials and published in numerous peer-reviewed journals. It is the most studied, evaluated elective procedure ever.”

He added, “I had a marine come back after deployment …[who] said he could see trip wires better in dim illumination, which he couldn’t with his smudged glasses.” Glasses can break the ear cup seal in a helmet, and in Iraq or Afghanistan, contacts can be difficult to wear with the hot desert sand blowing. The procedure has changed the lives of the men and women of our armed forces for the better.

Although improving the patient selection process was a focus of the FDA hearing, Schallhorn emphasized that lasik surgeons have been following selection procedures all along. A substantial percentage is turned away for not being good candidates. “The most important thing is that they understand what they’re getting into,” Schallhorn said. For example, 60-year-old patients will benefit from the procedure, but it won’t give them 20-year-old eyes.

Economics to blame

Since the FDA hearing, the number of people seeking lasik has gone down, but both Stonecipher and Schallhorn cited the downturn in the economy.

Over the years, technological innovations have made lasik safer and more effective. One such advance has been the femtosecond laser, which shoots out light at a rate of trillionths of a second, or femtoseconds. Before the introduction of the femtosecond laser to lasik, ophthalmologists cut the eyes with a sharp blade that fit into a precision device called a microkeratome. However, even a precision blade is still a blade, and a laser is much more precise. Studies bear that out.

A study that Stonecipher conducted on 20,000 eyes that he treated showed that he was four times less likely to have to redo the procedure when using the laser. He pointed out that the Intralase, which was the first femtosecond laser to be cleared by the FDA, operated at 10 kHz and could make the flap in 90 s. Now the device can perform the procedure in just 10 s because it operates at 150 kHz, so the duration of the operation has become shorter as well.

Schallhorn pointed out that the femtosecond laser can now help patients with trauma-induced scars on their eyes. Ophthalmologists have started using it to open up the eye so that they can implant from donors portions of the cornea called lamellar grafts.

Another major innovation has been wavefront-guided lasik. “It represents a paradigm shift in treatment,” Schallhorn said. Wavefront is what the optometrist measures when he or she asks you to look at an eye chart while changing lenses and other conditions. However, relying on patient feedback is subjective, and measuring the wavefront by changing lenses is indirect. “We’re no longer constrained by measuring aberrations like when you get your eye measured by an optometrist,” he said.

More precisely, the wavefront is the change in shape of the front of the lightwaves that hit the eye as they exit the cornea. Ophthalmologists can measure this wavefront more accurately and in less time using a device called an aberrometer, which passes eye-safe light through the eye and monitors as the light exits the eye.

Aberrometers have been used in astronomy for years but only recently have been applied to ophthalmology. In this application, the aberrometer programs how the laser will perform lasik: The variables are custom-tailored to the wavefront of a patient’s eyes. Some aberrations in the wavefront have familiar names such as nearsightedness and farsightedness. “The Hubble telescope had certain aberrations that didn’t allow the camera to focus,” Stonecipher said. “The same thing goes for the optical system.”

In conventional as opposed to wavefront-guided lasik, the laser settings, rather than being custom-tailored, are preprogrammed to suit all patients. Stonecipher said that not everyone – just people who have certain aberrations – will benefit from wavefront-guided lasik. He compared the situation with that of treating patients with Tylenol. “If you have a room with a hundred people, the ones that are going to benefit from the Tylenol are the ones with a fever. Those people that are 98.6, they’re not going to have any efficacy.”

Ophthalmologists also can measure the topography of the eye. Topographic features of the cornea, such as microscopic hills and ridges, can influence the wavefront shape. These microscopic features can cause an aberration like nearsightedness, but other people, such as some baseball players, have been shown to have sharper-than-normal vision because of aberrations.

As for the future of lasik, Stonecipher said that he wouldn’t be surprised if technicians took over the role of the physician in performing the procedure. He said that the laser technology has matured. He compared it with Dell, Gateway and IBM computers. All of them basically do the same thing but have slightly different strengths and weaknesses in certain areas.

In conclusion, the procedure was and is one of the safest and most effective routine surgeries. New technologies such as wavefront guidance and the femtosecond laser have improved the safety and efficacy of lasik even more. Lasik has changed many people’s lives dramatically for the better.

However, the procedure also has worsened the vision of some patients, creating serious problems in their lives. It has been alleged that lasik is such a financial success that it has clouded the judgment of some physicians, who have produced misleading advertising and have approved patients for the procedure even when these patients do not meet the selection criteria.

For analysis and commentary on the topic of lasik safety, be sure to check out the blog, As Shenkenberg Sees It, on photonics.com.

Who said doctors lead boring lives?

Ophthalmology isn’t the only thing that Schallhorn has done. He flew F-14s in the Navy before becoming a TOPGUN instructor and then an ophthalmologist. He said that he always planned to become a doctor but that this was something “wild and fun” to do after college.

Since leaving the top of the aviation world, Steve Schallhorn has become a leading surgeon.

Karl Stonecipher not only practices lasik but also has performed many clinical trials of the procedure for the FDA. Stonecipher’s two uncles, one a research-oriented cardiologist and another an agriculture expert, influenced his decision to perform FDA clinical trials. He has also given lectures and trained doctors overseas.

Karl Stonecipher conducts many clinical trials for the FDA.