EyeWorld Asia-Pacific June 2012 Issue

June 2012 10 EWAP FEATURE Custom LASIK by Jena Passut EyeWorld Staff Writer Wavefronts are all the rage, so where will topography-guided systems fit in? F or refractive surgeons, custom LASIK platforms are producing amazing results for patients with traditional spherical refractive error. So where will extremely customizable topography- guided platforms, which aren’t yet available in the U.S., fit in? Topography-guided platforms are used to treat patients with irregular corneas. “That’s really where you need the fingerprint identification of the cornea and to be able to treat every cornea for those specific defects,” said David Goldman, MD , assistant professor of clinical ophthalmology, cornea and external disease department, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Fla., USA. A recent report in the Journal of Cataract & Refractive Surgery reported that topography-guided LASIK results were excellent in patients who had a decentered ablation. “It’s a great technology that’s going to apply, I think, to a small percentage of patients, and those are the people who have some irregularity of the cornea where it’s so critical to measure the corneal topography and treat it specifically,” Dr. Goldman said. Wavefront-guided Wavefront-guided systems create a customized ablation profile by using three-dimensional measurements of the patient’s cornea. The wavefront map is then used to guide the laser to reshape the corneal surface and correct any abnormalities. Currently, there are two types of wavefront platforms. A wave of light is used in wavefront-guided platforms to measure the cornea’s optical abnormalities, while the laser corrects those aberrations and the treatment prevents the onset of further ones. Abbott Medical Optics (AMO, Santa Ana, Calif., USA) offers the iLASIK and VISX CustomVue platforms, while Alcon (Fort Worth, Texas, USA/Hünenberg, Switzerland) owns the Wavelight Allegretto Wave, and Bausch + Lomb (Rochester, NY, USA) offers the Zyoptix. For Louis E. Probst, MD , national medical director, TLC Laser Eye Centers, who uses the CustomVue and VISX systems, the results of custom LASIK have been nothing short of “mind blowing”. “It’s no question, for the standard patient, wavefront- guided is extraordinarily effective, particularly used in conjunction with IntraLase [AMO],” he said, adding that he gets “ridiculously incredible” results, such as 98% of patients seeing 20/16 (6/5) or better uncorrected post-op, 78 are 20/12 (6/3.5), and 50% are 20/10 (6/3). However, those are patients who went into the procedure with healthy corneas. “For problem patients, particularly those with keratoconus or ectasia, topography-guided treatment makes more sense,” Dr. Probst said. The technology, however excellent, is not without risks. “Custom-guided ablations do tend to take a little more tissue than your regular ablation profiles, so if you are doing a really high treatment or have a patient with a cornea on the thin side, you have to be a little more cognizant of that,” Dr. Goldman said. “You need to be aware of how much tissue you are taking or leaving the patient with for the residual stromal thickness.” One of the issues with the measurement is that it is static, while wavefronts are generally dynamic, said A. John Kanellopoulos, MD , associate clinical professor of ophthalmology, New York University, New York, NY, USA, and director of laser vision, GR Institute, Athens, Greece. “It is very difficult to make a conclusion that this measurement is the optimal wavefront of this patient and if I mimic the changes that the wavefront imaging determines, then I will have an optimal wavefront environment for the patient,” he said. Topography-guided Topography, on the other hand, is highly reproducible and can give a surgeon correction at the level he or she desires. “One of the differences when you treat irregularities, where you need a customized treatment, however, is that topography-guided does not have the brain cells, so to speak, to correct refraction,” he said. “The topography-guided system will give you a much better optical media as far as regularity and the IHD index of height decentration and IHA index of height asymmetry.” Dr. Kanellopolous said clinicians in Europe also see the value in using topography-guided LASIK as a hyperopic treatment up to +0.6 D. AT A GLANCE • Wavefront-guided and topography-guided, both used to reshape the cornea, are two very different LASIK platforms • Topography-guided LASIK, which is not yet available in the U.S., is used to treat patients with highly irregular corneas • Wavefront-guided LASIK has been shown in several studies to be highly effective for regular corneas This graphic shows the drop in enhancements once Dr. Probst started using the CustomVue. It went from around 6% to 2 or 1.5%. Source: Louis E. Probst, MD