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Topography-guided LASIK: A paradigm shift in refractive laser treatment www.eyeworld.org Surgical innovations designed to improve outcomes Supplement to EyeWorld Daily News, Monday, April 28, 2014 This supplement is sponsored by Alcon. R efractive surgery has advanced significantly in the past 2 decades. When it was first introduced, we were able to reduce or eliminate patients' dependence on glasses or contact lenses. In ex- change for spectacle independence, however, patients sometimes had to accept less than 20/20 uncorrected visual acuity (UCVA) and induced visual aberrations. Today, topogra- phy-guided treatment LASIK with the WaveLight Allegretto Wave Eye-Q Laser (Alcon, Fort Worth, Texas) can provide not only freedom from glasses and contact lenses, but also improved quality of vision. 1 There are several differences between topography-guided customized LASIK and wavefront- guided customized LASIK. Wave- front-guided customized LASIK has traditionally been based on wave- front measurements obtained by projecting multiple light beams into the eye and measuring the location of the corresponding light reflected from the retina. With topographers, we can measure many more points of curvature on the cornea over a wider area than is possible with wavefront measurement devices. For example, the Topolyzer (Alcon), used in conjunction with the WaveLight Laser, measures corneal curvature at approximately 22,000 locations on the cornea, while the WaveLight wavefront analyzer (Alcon) measures only 168 sites, and the WaveScan (Abbott Medical Optics, Santa Ana, Calif.) measures only 240 points per WaveScan technology specifications. Another benefit of topography is that measurements are not limited by the pupil. Wavefront measure- ments require light to reach the retina through the pupil, so the size and location of the pupil limits the area that can be measured. In contrast, corneal topographic measurements can be applied to the entire cornea. Additionally, highly aberrated eyes and those with corneal opaci- ties can produce inaccurate aberrom- eter measurements because aberrometers cannot always identify the source of light leaving the eye and because light may be scattered by the corneal opacities. In contrast, topography-guided treatment can be used successfully to evaluate highly aberrated eyes. Aberrometer measurements are also affected by the state of accom- modation (which can induce high- order aberrations in addition to spherical refractive changes), early cataract, and vitreous opacities. Surgical correction of lenticular high-order aberrations can be problematic because they tend to change with time. Additionally, wavefront-guided treatments do not necessarily compensate for off-axis rays of light passing through lenticular opacities from different locations on the cornea. Because corneal topography does not provide information about low-order optical abnormalities of the eye—spherical error and regular astigmatism—topography-guided re- fractive treatments cannot be based on corneal topography alone. For topography-guided treatment, re- fractive measurements of the eye's optical system must be obtained independently of topographic measurements. Topography-guided treatment software combines both refractive and topographic informa- tion to generate the pattern of laser shots that will improve vision. Study summary The Topography-guided Treatment Study Group recently investigated the visual outcomes of topography- guided LASIK. This prospective, non- randomized study was performed at 9 clinical sites in the United States and included 249 eyes of 212 patients with myopia or myopic astigmatism treated with topogra- phy-guided treatment LASIK using the WaveLight Allegretto Wave Eye-Q Laser. Outcome measures included manifest refraction, UCVA, best spectacle-corrected visual acuity (BSCVA), visual complaints, adverse events, responses to questionnaires, and complete ophthalmologic examinations. Patients included in this study were between the ages of 18 and 65 years (mean: 34 years) and had up to –9.0 D of spherical equivalent myopia at the spectacle plane with up to 6.0 D of astigmatism, cor- rectible to at least 20/25 in each eye. Doyle Stulting, MD, PhD This supplement was produced by EyeWorld and sponsored by Alcon. The doctors featured in this supplement received compensation from Alcon for their contributions to this supplement. Copyright 2014 ASCRS Ophthalmic Corporation. All rights reserved. The views expressed here do not necessarily reflect those of the editor, editorial board, or the publisher, and in no way imply endorsement by EyeWorld or ASCRS. by Doyle Stulting, MD, PhD Please refer to pages 6, 7, and 8 for important product information about the Alcon products described in this supplement. " With topography- guided treatment, we should tell our patients there is an excellent likelihood that they will have better vision without correction than they had preoperatively with correction and that the quality of their vision is likely to improve. " continued on page 3 Figure 1: Cumulative postop UCVA (ETDRS)

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