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T opography-guided ablations have been an integral part of my practice for a dozen years. My primary practice is based in Athens, and topography- guided ablations are time-tested and common outside the U.S. Now, with the FDA's approval of topography-guided custom ablation treatment (T-CAT) for eyes with myopia and myopic astigmatism, topography-guided LASIK ablations are an option here in the U.S. 1 A new paradigm The FDA study of topographic-guided refractions in virgin eyes establishes a new paradigm of even better outcomes by ultimately enhancing even corneas that we consider normal. An intrinsic advan- tage of topography-guided ablations became evident as a result of the phase 3 clinical study that was the basis for T-CAT approval: A large percentage of eyes gained lines of vision. 1 This is probably associated with the subtle cornea irregularities that even normal eyes have. These irregularities are addressed by topography-guided ablations, which by definition can normalize any cornea to maximum symmetry and apply the correction on the cornea apex (taking into account angle kappa). The differences between wavefront-guided methods and topography-guided methods are quite simple; wavefront-guided removes a lot of tissue to make a cornea more spherical based on the flattest part of the cornea. Topography-guided methods "shave" off the peaks of cornea curvature and aim to steepen flatter areas by ablating around them and indirectly steepening those flatter areas. This bimodal approach of simultaneous hyperopic and myopic treatment provides an advantage, in my opinion, because it removes much less tissue. In some instances, one-third less tissue is removed with topographic-guided ablations than with wavefront-guided ablations. I find topography-guided methodology much easier to understand than wavefront-guided methodology. Wavefront is an approach dependent on theory that I cannot necessarily grasp by looking at objective topography data. John Kanellopoulos, MD Beneficial for routine cases Even as a seasoned topography-guided surgeon, I have learned a great deal from the FDA study data that further supports my reliance on topography- guided methodology. The findings show that T-CAT is beneficial for virgin eyes, and this has led me to use it even in my routine LASIK cases. I see a significant advantage in the fact that in "normal" corneas T-CAT can normalize the cornea and offer better visual acuity and more lines of gained vision (Figure 1). For this as well as the reasons stated earlier, I consider topography-guided treatment to have advantages over wavefront-guided treatment. Reference 1. FDA device approvals website, Topography-guided Custom Ablation Treatment or T-CAT Summary of Safety and Effectiveness Data (SSED), available at: www.fda.gov/MedicalDevices/ProductsandMedical- Procedures/DeviceApprovalsandClearances/ Recently-ApprovedDevices/ucm372964.htm. Figure 1: These scans illustrate a –6 D female who underwent routine femtosecond laser LASIK with the Alcon Refractive Suite. The right eye was treated with T-CAT, and the left eye with wavefront-optimized. The IHD values improved in the right and deteriorated slightly in the left, perhaps explaining the improvement in UCVA in the right from CF (CDVA 20/20) to 20/10 and in the left from CF (CDVA 20/20) to 20/20. Two lines were gained in the OD and no lines gained in the OS; these corneas would be classified as normal, but the slightly steeper superior half benefited from the T-CAT normalization, and this improved the visual outcome. Why I believe in topography- guided ablations by John Kanellopoulos, MD Dr. Kanellopoulos is director of the Laser Vision.gr Eye Institute, Athens, Greece, and clinical professor of ophthalmology, New York University School of Medicine. He was a pioneer internationally with T-CAT LASIK and other topography-guided excimer applications performed with the Alcon WaveLight ALLEGRETTO WAVE Eye-Q and EX500 excimer lasers. Dr. Kanellopoulos is a consultant for Alcon. He can be contacted at ajk@brilliantvision.com. 2 A monumental stride forward in refractive outcomes For important product information about the WaveLight Excimer Laser System, please see page 6.

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