Eyeworld

43 EW REFRACTIVE July 2017 100 µm in myopic ablations starts to become significant and may induce mesopic and scotopic aberrations," Dr. Kanellopoulos said. Conventional laser treatments Wavefront-guided and wavefront- optimized treatments are not ideal for all patients, so there is still a place for conventional laser treat- ments. "One of the challenges is that in patients who are pseudophakic or who have irregular corneas, it is sometimes difficult to capture a high quality wavefront measurement. It depends on the wavefront technol- ogy," Dr. Trattler said. "For example, the original VISX device, called WaveScan, has difficulty obtaining a high quality capture in pseudopha- kic patients. In comparison, a newer technology called iDesign [Johnson & Johnson Vision] measures five times more points, so it provides higher density of measuring. The iDesign can capture higher quality wavefront images, and can provide an accurate measurement, as well as a non-subjective refraction, in patients who are pseudophakic." "It's nice for surgeons to have a lot of tools in their toolbox so that they can fit the technology to the patient rather than fitting the patient into the technology," Dr. Greenwood said. "For most eyes, both treatments are going to be good. For patients who have a lot of pre-existing higher order aberra- tions, wavefront-guided treatment is a better option. But in general, they both provide good outcomes with minimal induction of higher order aberrations, which means good quality of vision following the procedure." EW Editors' note: Dr. Gordon and Dr. Kanellopoulos have financial interests with Alcon. Dr. Trattler has financial interests with Alcon, Bausch + Lomb (Bridgewater, New Jersey), and Johnson & Johnson Vision. Dr. Greenwood has no financial interests related to his comments. Contact information Greenwood: Michael.greenwood@vancethompsonvision. com Gordon: mgordon786@gmail.com Kanellopoulos: ajkmd@mac.com Trattler: wtrattler@gmail.com round beam is on a curved surface, coming again tangential, it becomes ovalized. The energy characteristics change, meaning the energy density changes because now it's a bigger spot size but the same energy. Now we're delivering less energy to any given spot. Because of those two characteristics, we weren't getting as much energy as we needed delivered to the peripheral cornea, which basically generated more spherical aberration than one wanted. People with big pupils, in particular, would have night glare issues. Wavefront optimization was a way to deliver more energy to the peripheral cor- nea to compensate for the loss in a scanning spot laser," he explained. Dr. Trattler noted that wave- front-optimized treatments were developed after evaluating postop- erative LASIK results and making adjustments in the algorithm for treating and reshaping the eye to improve the quality of vision by improving the transition zone of the treatment, which is the area be- tween the optical zone and the rest of the cornea. "One of the arguments regard- ing use of wavefront-optimized over wavefront-guided treatments is that normal eyes do not usually have higher order aberrations. Therefore, it would not make sense to employ wavefront-guided treatment, which could induce higher order aberra- tions due to capture and/or delivery error," said A. John Kanellopoulos, MD, professor, New York University, and medical director, Laservision.gr Institute, Athens, Greece. "Potential parameters that may induce higher order aberrations include the LASIK flap, decentration of the excimer ablation, and irregularities in the ablation." The use of the femtosecond lasers for flap creation has reduced wavefront deviations for most LASIK patients. The reduction in flap-relat- ed aberrations may be the strongest indication for the use of femtosec- ond lasers in flap creation in LASIK. Laser centration is also a con- cern. The latest laser trackers have higher frequencies and therefore faster response times. "Centration, especially for myopic ablations, has been more important than matching pupil size in determining quality of vision in mesopic and scotopic pupils. A decentration of more than Register Now: www.icoph.org/WOC2018

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