EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/422211
71 December 2014 EW MEETING REPORTER white measurements, the center of the undiluted pupil and other land- marks on the eye; surgical planners that combine biometric IOL calcula- tors and astigmatism correction cal- culators; and data transfer systems. "Manual marking has always been a challenge," Dr. Espiritu said. Digital markers aren't yet perfect— among other things, companies are currently working on integrating posterior corneal curvature mea- surement into their systems—but they allow the exact, reproducible positioning of main, paracentesis, bimanual, and arcuate incisions, capsulotomy, and toric IOLs that is a challenge with manual marking. Representing the ASCRS, Dr. Hill discussed "IOL Power Labeling and Predictability," examining how various factors such as the use of optical biometry, advanced ker- atometry, modern IOL power formu- las and calculators, retinal thickness variations around the fovea, variable capsulorhexis size, and 0.50 D and 0.25 D step premium IOLs influence mean absolute refractive error. Taking each factor in turn did not significantly influence mean absolute refractive error. Rather, the surgeon must optimize all component parts. "One part perfect does not make the whole perfect," Dr. Hill said. He highlighted the essential paradox of optimizing the optical system: making one part "good" won't improve the whole significantly; however, getting one part "bad" will guarantee a refractive surprise. Dr. Hill concluded from this special 0.25 D step study that "the absolute error for a series of patients is imperceptibly improved for IOLs in 0.50 D and 0.25 D steps. "With current technology, there appears to be no clinical advantage for implanting IOLs in 0.25 D steps as there is no detectable improve- ment in refractive accuracy," he said. However, Dr. Barrett pointed out that for the surgeon, while it might not make sense intellectually, being able to implant IOLs as close as possible to the precise target refractive correction provides a measure of comfort. Dr. Hill agreed, and suggested one solution that he believes should make everyone happy: Every IOL should be labeled with its exact IOL power. Representing the ESCRS, Damien Gatinel, MD, Paris, discussed the customization of aberration correction. In defining "customization," Dr. Gatinel distinguished the term from "conventional"—he equated the latter to wavefront optimization. Customization, on the other hand, is achieved through wavefront or topography guidance and aspherical customization. In assessing visual outcomes, he said that measuring visual acuity is less discriminating than measuring visual quality, examining higher-or- der aberrations, contrast sensitivity, and the presence of visual distur- bances such as halos and glare. Customization, he said, requires a balance between 2 sometimes contradictory aims for the refractive surgeon: optical quality and visual performance. Privileging one sacri- fices some of the other. Multifocal IOLs, he said, were developed in an attempt to improve both at the same time. Representing ALACCSA-R/ LASCRS, Luis Izquierdo Jr., MD, PhD, Lima, Peru, discussed the im- portance of angle kappa in avoiding postoperative surprises. Angle kappa is the angle between the visual axis and the pupillary axis. This has some practical, clinical consequences. For instance, it is assumed that in patients with higher angle kappa, multifocal IOLs induce more aberrations. The bigger the central zone diameter of the IOL, the higher the angle kappa must be to reach the edge of the first ring of the IOL. If a patient has a high (greater than grade 7) positive (the pupillary axis is temporal to the vi- sual axis) angle kappa and a shallow anterior chamber, Dr. Izquierdo said, consider not implanting a multifo- cal IOL. On the other hand, for IOL decentration, the surgeon need not worry if it is decentered toward the visual axis. Femtophaco symposium compares laser preferences During the "Facets of Femtophaco" session, advocates for various lasers spoke about why they prefer each product. What's interesting is that more and more lasers are coming on the market, said Ronald Yeoh, MD, Singapore, one of the chairs of the session, and it's hard to tell which is the best. Sri Ganesh, MD, Bangalore, India, spoke about why he prefers the Catalys (Abbott Medical Optics, Abbott Park, Ill.) laser. First, he said, it's very easy to plan, with a template-based planning software. It also has a liquid optics interface, which Dr. Ganesh said is one of the most important parts. The Catalys has an integral guidance system, which has a 3D volume OCT and a laser designed specifically for cataract surgery. Using the Catalys, Dr. Ganesh has treated a total of 262 eyes. John Chang, MD, Hong Kong, discussed both why to use the fem- tosecond laser and why to specifi- cally use the LENSAR (Orlando, Fla.) system. With femto, he said that the capsulotomy is more precise, it's particularly good in difficult cases, nucleus splitting is much easier, there is less phacoemulsifi- cation power, there is less corneal endothelial cell loss, there is less IOL decentration, and there are arguably better visual and refractive outcomes. Specifically with the LENSAR, Dr. Chang likes that it is a small, compact machine the can be easily moved around. It has a small suc- tion ring, with an even smaller one set to come out. The capsulotomy is free floating most of the time, and there is no capsular block syndrome. "It's very easy to use," he said. Mahipal Sachdev, MD, Delhi, India, spoke about why he likes the LenSx laser (Alcon, Fort Worth, Texas). He presented 5 key factors of why he prefers the LenSx, which included the variable beam profile, the design, the patient interface, the high definition OCT, and the innovation associated with the system and company. In terms of the variable beam profile, "the laser is optimized for each specific tissue depth," Dr. Sachdev said, so it provides effective incisions. The laser is also designed with patient flow, ergonomics, and flexibility in mind. It's more intu- itive and user friendly and makes the fixed bed obsolete, he said. The patient interface provides fixation without applanation. The high definition OCT scans the entire anterior chamber in a single scan, and the real time OCT provides a continued on page 72 View it now: APACRS 2014 ... EWrePlay.org Dan Reinstein, MD, London, discusses the practical advantage of leaving a modest degree of spherical aberration.