REFRACTIVE 22 EWAP DECEMBER 2022 for those doing laser vision correction. The laser treatment takes into consideration all the wavefront aberrations from the measurements to help guide treatments. It’s also important to make sure you’re optimizing the ocular surface. Dr. Trattler said that any significant dry eye or MGD could throw off wavefront readings, so it is important to address the ocular surface ahead of time. Dr. Trattler uses wavefrontguided treatments in most of his laser vision correction cases, particularly for younger patients. It may be difficult to get a good wavefront capture in patients who are pseudophakic because there may be a reflection off the IOL during the testing, which makes the results less reliable. EWAP Editors’ note: Dr. Trattler practices at the Center for Excellence in Eye Care, Miami, Florida, and has interests with Alcon and Johnson & Johnson Vision. Chandra Bala, MD Clinical Associate Professor Level 2, 33 York St., Sydney NSW 2000, Australia bala@personaleyes.com.au ASIA-PACIFIC PERSPECTIVES T h e goal of my refractive surgery practice is to achieve the best possible vision from an eye. This requires the consideration of various factors including the eye outside paraxial optics where aberrations start to exert a greater influence. Zernike polynomials which are now part of everyday clinical vernacular offer an insight into the visual performance by ascribing numerical values to clinically relatable entities such as coma and secondary astigmatism. Surgeons find these entities relatable. The caveat is that the wavefront is an approximation of the visual experience at one wavelength for a circular pupil and uses a finite number of polynomials. It can never be the totality considered in isolation. The correction of wavefront error, however, affords me an opportunity to go towards a vision of 20/10. Currently, we use ray tracing technology from Alcon which was initially tried a decade ago by Schumacher et al. (J Cataract Refract Surg 2012; 38:28–34). Biometric measurements such as axial length, ACD, anterior and posterior corneal tomography are used to create a base optical model of the eye. The refractive indices and the posterior lenticular surface characteristics are assumed based on published literature. The model is then altered by changing the lens shape so that the wavefront of the eye model approaches the measured wavefront. The resulting a personalized eye model or an “eyevatar” is then used to plan the excimer laser treatment. This technology uses wavefront measured at 380 points in a 6.5-mm pupil along with the biometry data to create the eyevatar rather than the classical treatment which uses sphere, cylinder, and axis. Furthermore, wavefront-based treatments in the past assumed that all patients with the same wavefront processed light the same way. However, wavefront is only the final product of various elements at various distances inside the eye and by incorporating the biometric data the rays of light can be traced to give a better understanding of how the light is processed and therefore a customized treatment can be designed, mitigating the large increase in aberrations seen previously. Presently, we are limited in using this technology to treat myopes with or without astigmatism. In our series of 400 eyes using this new ray trace technology over this year, we have achieved 20/10 vision in 13% of patients and cumulatively 20/12.5 or better in 49% and 20/16 or better in 89% and 20/20 or better in 99% of eyes. Our touch-up rate is now at approximately 0.8%. This technology has truly customized the treatment not for each patient but for each eye and allows us to chase the elusive supervision of 20/10. Editors’ note: Dr. Bala is a consultant for Alcon and Johnson & Johnson. ADVERTISER LISTING Alcon Page 2 www.alcon.com Feather Page 20 www.feather.co.jp/en/ APACRS Page 5, 6, 37, 43, 44 http://www.apacrs.org
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