EyeWorld Asia-Pacific March 2011 Issue

22 March 2011 EW REFRACTIVE Optimized outcomes for hyperopic LASIK by Maxine Lipner Senior EyeWorld Contributing Editor Homing in on the optimized approach H yperopic LASIK results with the wavefront- optimized Allegretto laser (Alcon, Fort Worth, Texas, USA/Hünenberg, Switzerland) outdid those with the conventional LadarVision 4000 (Alcon) with regard to visual outcomes, recovery, and residual cylinder, according to Daniel S. Durrie, MD, clinical professor of ophthalmology, University of Kansas, Overland Park, Kan., USA. Results published in the May issue of the Journal of Refractive Surgery pegged 65% of eyes treated with the wavefront-optimized approach as attaining 20/20 (6/6) acuity on post-op day 1 versus just 20% of eyes treated with a conventional profile. From the start, wavefront- optimized lasers have used a different tack from conventional lasers, taking spherical aberration into account. “When surgeons started doing the first patients they noticed that with the wavefront devices, not all of the spherical aberration was being treated,” Dr. Durrie said. “Spherical aberration is one of the main higher-order aberrations that previous lasers did not address very well. They changed the algorithm of the laser so it does a better job of not inducing spherical aberrations.” They looked at data using wavefront analysis of previous patients and were then able to adjust the treatment algorithm to optimize different amounts of needed correction based on wavefront information. Wavefront-guided correction is individualized for each patient’s eye. “That measures the higher- order aberrations and the lower- order aberrations and tells the laser what to do,” Dr. Durrie said. “But even those corrections in previous lasers were still inducing spherical aberrations.” Optimized advantages When he initially launched this study, Dr. Durrie wanted to see what advantages his newly acquired Allegretto laser (formerly the WaveLight) might have for treating hyperopia compared with others already on the market. In particular, he wanted to take on hyperopia because he saw that as lagging behind in development compared to myopia and astigmatism. “I wanted to see if this new kid on the block could compare to my standard at that time, the CustomCornea laser (Alcon), with wavefront-optimized hyperopia surgery,” he said. “This laser was generally accepted in the market as being a top-notch hyperopia laser.” Included in the prospective, randomized trial were 51 consecutive hyperopic eyes. Of these, 25 were treated with the LADAR4000 excimer laser and 26 with the Allegretto. Investigators found that at six months, 84% of those treated with the wavefront- optimized approach had attained 20/20 acuity versus 72% of those who underwent conventional treatment. When it came to cylinder, there was a mean of just –0.17 D for the wavefront- optimized group versus –0.41 D for eyes that underwent conventional treatment. Dr. Durrie was very encouraged by results from both of the lasers for the treatment of hyperopia. “The results were very good and the 20/20 rates were significantly higher than had been reported with previous hyperopia lasers,” he said. “This was probably the first time that the Allegretto laser became really interesting to me because I took on the hardest patients and it did well on them.” There are several reasons why the optimized approach tends to be more successful, Dr. Durrie said. Essentially, the approach changes the algorithm to add more pulses to the peripheral part of the ablation, which are needed. “From a technical standpoint what we found is that the cornea is curved and more of the pulses in the periphery are reflected than we initially thought,” he said. “We were almost inefficient in how well we were ablating the mid- periphery.” Also, the shape of the laser pulses in this portion of the cornea was a factor. “When you take a laser pulse that is round and you hit it on the side of a hill it turns oval,” Dr. Durrie said. “Not only was some of the energy reflected, but the spots were not round if they were hitting on the side of the hill so they weren’t as efficient.” More recent lasers have incorporated this idea of adding pulses. “As the next generation of software is being developed, more pulses are being put in the periphery than the original algorithms because they calculated for flat surfaces,” Dr. Durrie said. Allegretto presents a viable option for hyperopic LASIK Source: Alcon Weighing approaches It is Dr. Durrie’s view that all patients can ultimately benefit from the idea of optimizing correction by adding pulses in the mid-periphery. “In my practice, I use wavefront-optimized surgery on the vast majority of patients—90–92%,” he said. “I use wavefront-guided for the people who have a lot of higher aberrations preoperatively.” He stresses that deciding which approach to choose these days is very laser-dependent. “With the VISX (Abbott Medical Optics, AMO, Santa Ana, Calif., USA), wavefront- guided surgery has proven to be the best software and should be used on all patients who qualify,” Dr. Durrie said. “If you have an Allegretto laser, wavefront-guided surgery is the better procedure for those people who have a lot of higher-order aberrations, but it is not necessary for everyone because of the wavefront-optimized software that is built into the laser.” Dr. Durrie finds that when it comes to the idea of wavefront optimization, laser manufacturers play on their strengths. “Alcon says that you don’t need to use wavefront-guided surgery other than in a few patients and that is correct,” Dr. Durrie said. “AMO says that wavefront-guided surgery should be used on everyone and that is correct if you have a VISX laser.” Ultimately, Dr. Durrie agrees with both and is optimistic about what this means. “They’re both right,” he said. “I think that it’s important for ophthalmologists to understand that we have fabulous lasers on the market right now and all of them get extremely good results.” EW Editors’ note: Dr. Durrie has financial interests with Abbott Medical Optics (Santa Ana, Calif., USA) and Alcon (Fort Worth, Texas, USA/Hünenberg, Switzerland). Contact information Durrie: 913-491-3737, ddurrie@durrievision.com