EyeWorld India December 2014 Issue

58 EWAP NEWS & OPINION December 2014 interpolation, Dr. Hill concluded. “When we have this much sensitivity and this much accuracy, we can begin to do things that have not been done before.” Perfect Cut, Clarity, Prediction The Combined Symposium of Cataract and Refractive Societies (CSCRS) is a unique forum where the major regional societies—the APACRS, the American Society of Cataract and Refractive Surgery (ASCRS), the European Society of Cataract and Refractive Sugeons (ESCRS), and the Latin American Society of Cataract and Refractive Surgery (ALACCSA-R/LASCRS)— join forces. The first CSCRS was held at the 2005 APACRS annual meeting in Beijing, and has since been held at the annual meetings of the involved societies. “For us, it’s the highlight of our meeting,” Dr. Barrett, president, APACRS, said. This year, the CSCRS focused on the various strategies and technologies that allow surgeons to create that “perfect cut” to achieve “perfect clarity” and “perfect prediction.” In Dr. Barrett’s talk on “Toric IOL Prediction,” he focused on ways to optimize outcomes with toric IOLs. First, Dr. Barrett recommended using three devices to assess every patient: one primary (an optical biometer) and two secondary (a topographer and a manual keratometer). Next, toric IOLs require that surgeons measure surgically induced astigmatism (SIA) and axis alignment. When measurements of these parameters are for whatever reason not available, surgeons can base their refractive target calculations on assumptions of one or both. However, in a study of 54 eyes, Dr. Barrett found that using known (measured) SIA with assumed axis alignment provided substantial improvement over calculating with both assumed SIA and assumed axis alignment; measuring both further improved outcomes, but not as substantially. Finally, in terms of alignment, Dr. Barrett described the use of the toriCAM app he developed together with a macro lens and a felt tip pen. The app converts the surgeon’s mobile device into a digital marking aid. Exploring digital markers further, Cesar Espiritu, MD , Metro Manila, Philippines, talked about these devices that allow surgeons to place incisions and align toric IOLs “where they should be.” Specifically, he described the components of current digital markerless systems: an image-guidance system that use conjunctival blood vessels, iris characteristics, white-to-white measurements, the center of the undiluted pupil and other landmarks on the eye; surgical planners that combine biometric IOL calculators and astigmatism- correction calculators; 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 measurement 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—the use of optical biometry, advanced keratometry, modern IOL power formulas 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 improvement 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, France, 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- order aberrations, contrast sensitivity, and the presence of visual disturbances 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 sacrifices 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., Jewels - from page 57