EyeWorld Asia-Pacific March 2016 Issue

March 2016 11 EWAP Feature Views from Asia-Pacific Jodhbir S. MEHTA, BSc(Hons), MBBS, MRCOphth, FRCOphth, FRCS(Ed), FAMS Head, Corneal and External Eye Disease Service Senior Consultant, Refractive Service Head, Tissue Engineering and Stem Cells Group, Singapore Eye Research Institute Singapore National Eye Centre 11 Third Hospital Avenue, Singapore 169751 Jodhbir.s.mehta@snec.com.sg T opography-guided treatments offer the physician a technique to improve best-corrected spectacle visual acuity by reducing irregular astigmatism. The concept itself seems to be correct in the fact that you are treating the irregularity of the cornea in the cornea as opposed to the whole wavefront of the eye. In my own practice I think topography-guided LASIK is particularly useful in managing patients who have had prior refractive surgery complications, e.g., small optical zones, treating induced irregular astigmatism, and decentered ablations causing glare and halos. However, as the articles describe the treatment itself is not as straightforward as wavefront treatments. The key is to generate accurate and consistent topography before undergoing any ablation treatment. This may require the acquisition of 6–8 good quality scans in order to get sufficient consistency before proceeding with any treatments. Optimization of the ocular surface to provide a good tear film is important and correct positioning of the patient will improve success in this area. However, this is easier said then done especially on diseased corneas, i.e., those with high irregular astigmatism where scan consistency can be difficult. We use the EX500 Wavelight laser system (Alcon, Fort Worth, Texas) at SNEC and my experience has been that it does require some normogram adjustments following topography acquisition to get accurate results. Once the topography has been uploaded or transferred to the machine the surgeon must remember that the ablation will be centered on the corneal apex, not the pupil center, so some adjustments maybe required. Currently, there are many reports in the literature on topography-guided PRK with or without collagen crosslinking, which seems to be a more appealing option for the refractive surgeon especially in cases of post-keratoplasty astigmatism or in patients with keratoconus. I prefer this option in my post-keratoplasty patients (combined with MMC) since the creation of a LASIK flap alone in these patients without any ablation has been shown to induce significant aberrations. However, the long-term success of surface ablation and collagen crosslinking is still lacking in the literature and we really need good quality clinical studies to really understand the effect of weakening an already pathologically unstable, biomechanically weak cornea, even if this is combined with crosslinking, on the long-term stability of the refractive outcome. Editors’ note: Dr. Mehta declared no relevant financial interests. will provide a 4-hour training program required for surgeons who want to get started with this platform. Following the training, all participants will be qualified by Alcon clinical applications specialists to perform the procedure. The Contoura system is currently indicated and approved only for myopic patients with or without astigmatism who have not had previous corneal surgery. Dr. Solomon recommends starting off with patients who have virgin eyes and normal corneal topography. “If someone is looking to do topography-guided LASIK, I would recommend that they start out with normal corneas—virgin eyes—and get used to the process of how to take a topo-guided measurement,” Dr. Solomon said. “As with most things in medicine, there’s a lot of art to this science. There are nuances for the staff to learn how to take good measurements and for surgeons to understand when they are getting repeatable measurements,” he said. “I think topography-guided LASIK has a lot of potential for the right patients, provided we know when to accept good data, and when we have good surgical planning,” he continued. “It’s not cookie-cutter at all. It’s a process. But provided we get all those things in order, patients are going to do very well.” David Lin, MD, FRCSC, medical director, Pacific Laser Eye Centre, and clinical associate professor, University of British Columbia, Vancouver, has been performing topo-guided ablations since 2001. He advises that when starting out, surgeons be very selective in choosing which patients to operate on. He said that topography-guided ablations make up only 2.3% of all the LASIK cases he performs. “It’s a tiny amount because the regular wavefront-optimized LASIK results we found were better for normal eyes,” he said. “If you have a normal eye, there’s really no reason to do a topographic LASIK treatment.” Dr. Lin only performs topo-guided treatments for decentered ablations, optical zone enlargements, patients with keratoconus or patients post- keratoplasty or radial keratotomy (RK). For most of these patients, however, he chooses to do PRK rather than LASIK. “My philosophy is that if the eye is already asymmetrical and aberrated from weakening, in this case, they should not have LASIK because LASIK weakens the eye even more.” Although both topo-guided LASIK and PRK are available internationally, only topo-guided LASIK is FDA-approved at this time. Another thing to keep in mind is that flap creation is slightly different for topo-guided ablations. “Topography-guided continued on page 12