August 2015




Keratorefractive surgery

Modern LASIK by the numbers

by Maxine Lipner EyeWorld Senior Contributing Writer


Not everyone feels they have perfect outcomes, but the percentages are extremely high of people functioning very well. Peter J. McDonnell, MD


Quantifying patient perspectives and beyond

Just how effective is modern LASIK with current state-of-the-art technology? EyeWorld is drilling down on study results that take patients perspectives into account, as well as more traditional data. The recent PROWL 1 (Patient- Reported Outcomes With LASIK) and PROWL 2 studies assessed patient satisfaction with wavefront- guided and wavefront-optimized ablations and put numeric perspective on this. The idea behind this 2-pronged study was to shine a light on the impact that the surgery has on patients, according to Peter J. McDonnell, MD, William Holland Wilmer professor and director, Wilmer Eye Institute, Johns Hopkins University, Baltimore. Some resistance to refractive surgery goes back to the old days of radial keratotomy. There have been people who are tremendous adherents, who have had surgery and feel that it is very positive and even transformative for them, he said. There has also been a vocal minority of people, however, who feel there have been problems. When PRK came along, such issues diminished, but with LASIK these concerns resurfaced in some corners.

Patients perspective

In an effort to generate more light and less heat and to have actual data, efforts have been underway to try to measure more accurately the impact of refractive surgery on patients lives, Dr. McDonnell said, adding that the PROWL study included not only easy-to-measure factors such as visual acuity but also patients reports of their ability to function under different circumstances.

The study included a military and a civilian population, with the military-based PROWL 1 consisting mostly of young, healthy males, and PROWL 2 more apt to include older civilians, Dr. McDonnell said. These populations were very different. Young military recruits tend to have fewer issues like dry eye, which may be a particularly important consideration in refractive surgery, and the civilian population tended to be older, more female, he said, adding that older females in particular are more likely to have dry eyes, which can be problematic for refractive surgery. So examining these two different populations was very helpful. Traditional results from this study at 6 months indicated that following LASIK, 99.5% of patients had 20/20 binocular acuity or better, with 76% attaining acuity of 20/12.5 or better. The study also included patient-reported outcomes, something Dr. McDonnell views as very important. The way we measure visual acuity on a high contrast acuity chart may be reproducible and consistent among offices, but patients dont live in our exam lanes, he said. They live out in the real world. If you want to truly know how successfully patients are functioning, why not ask them? Thats what the instruments in the PROWL studies were designed to do.

The results gleaned here were encouraging, he said. While there are some people who report issues like glare and halos early on after surgery, if we look at how people do over time, issues like glare, halos, and ghost images 6 months after surgery were either at or below the level that patients had prior to surgery, Dr. McDonnell said. At 6 months, 98% of patients said they were satisfied or very satisfiedonly 2% were dissatisfied. Dr. McDonnell thinks this is reassuring. Not everyone feels they have perfect outcomes, but the percentages are extremely high of people functioning very well. He sees the results as substantiating the idea that practitioners are providing patients with outstanding LASIK outcomes. Still, the smart ophthalmologist understands that patient selection and preop education are a key part of the process. The PROWL studies by no means take away the importance and the duty of surgeons to carefully evaluate patients as surgical candidates, Dr. McDonnell said. It doesnt guarantee wonderful outcomes, but it can reassure us that for appropriate candidates, appropriately performed LASIK has a high margin of safety and a high degree of efficacy.

Evolving approaches

In addition to wavefront-guided and wavefront-optimized approaches, other modern LASIK approaches have emerged. In May the iDesign Advanced WaveScan Studio System (Abbott Medical Optics, Abbott Park, Ill.) received FDA approval. This system is used to capture information on any given patient and drives a customized treatment, according to Stephen C. Coleman, MD, in private practice at Coleman Vision Center, Albuquerque, N.M. The technology, which uses wavefront diagnostic aberrometry to pinpoint imperfections in the eye, relies on more data points than ever before. There are currently 1,250 data points that are provided on the cornea as opposed to the WaveScan, which was about 250, he said. Dr. Coleman thinks this new technology offers better outcomes and decreased enhancement rates. My feeling has always been that the single most important number in a practice is the enhancement rate, he said. Its incumbent on the surgeon to keep that number very low for a variety of reasons. When he took part in the FDA trial for the iDesign, he had excellent results. I have a zero enhancement rate for my cohort of patients and my outcomes were tremendous, he said. The quality of vision in the iDesign study was also outstanding, he said. Patient questionnaires showed decreased halos and glare. My general sense is that the quality of vision is improved with the iDesign because there are more data points and the way that the treatment profile is laid down on the cornea is more customized, more accurate, he said.

Another unique approach now in use is topography-guided LASIK. Arthur B. Cummings, MD, Wellington Eye Clinic, Dublin, Ireland, explained that the technique can be applied to regularize the cornea while correcting the refractive error. Consider doing a wavefront-guided procedure with an eye that has wavefront errors despite having a perfect cornea. After the procedure, the cornea will be irregular to compensate for the intraocular irregularities. With topography-guided, thats not the casethe cornea is always made more regular, Dr. Cummings said. This offers the potential to get better results with customized, primary treatments. In addition, the topography maps are repeatable. You can take 10 topography maps and the 10 will almost look identical, he said.

The topography-guided approach adds significant value to retreatment, he said. For patients who have a decentered ablation or a small optical zone, this approach works best, he stressed. With wavefront corrections, the only option practitioners have is to strive for emmetropia and attempt to remove all aberrations, Dr. Cummings explained. The topography-guided approach, however, offers flexibility in regularizing the cornea. With topography-guided ablations, physicians have the ability to make the optical zone size any size in 0.1 mm increments, he explained, adding that it is not necessary to use quarter diopter increments as it is with wavefront-optimized; with topography-guided, the refraction can be entered in 1/100ths. With topography-guided procedures, the final asphericity can also be controlled by adjusting the Q-value target. Dr. Cummings described the results from the topography-guided trial in the U.S. that led to the FDA approval of the WaveLight Allegretto Wave Eye-Q (Alcon, Fort Worth, Texas). These indicated that at 3 months, 93% of eyes were 20/20 or better, 69% were 20/16 or better, and 32% were 20/12.5 or better. These results highlight the power of regularizing the cornea during laser refractive surgery.

From a clinical perspective, he thinks that primary topography- guided LASIK with its very good outcomes has the potential to get patient referrals going again. LASIK has taken a bit of a beating in the last few years, he said. Now we might suddenly find thats changed with better outcomes. Also, Dr. Cummings said the approach can be used to repair results of LASIK cases gone awry. When people start seeing the value of topo-guided as a repair tool, it will take the worry away from patients who currently arent having LASIK done for fear of some sight-damaging complications, he said. Going forward, Dr. Cummings thinks there is one more important technology in the wingsray tracing. This does what topography-guided LASIK can do but also includes refractive modeling of the eye, he explained. All of the other technologies irrespective of their diagnostics apply the data to a generic eye (Gullstrand model). Ray tracing uses a virtual model of the patients own eye as represented by data points from devices providing corneal, wavefront, biometric, and refractive data, he said, adding that the results will likely be even more accurate. But the advent of this is still a couple of years away.

Editors note: Dr. Cummings has financial interests with Alcon. Dr. McDonnell has financial interests with Allergan (Dublin, Ireland) and GrayBug (Baltimore). Dr. Coleman has no financial interests related to this article.

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