MAY 2013

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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12 Supplement to EyeWorld May 2013 Managing residual refractive errors by David F. Chang, MD David F. Chang, MD " Emmetropic outcomes are particularly crucial with multifocal IOLs. " The most common cause of patient dissatisfaction is not always avoidable, but it is treatable W hen it comes to patient satisfaction, we cataract surgeons have historically been spoiled. Who among us tires of hearing patients rave about how easy and painless the operation was; how quickly the vision improved; and how color, brightness, and uncorrected vision are so surprisingly good? Indeed, we've become very accustomed to routinely exceeding the expectations of our cataract patients. Offering cataract patients the choice of refractive IOLs and adjunctive refractive options, such as astigmatic keratotomy or the femtosecond laser, suddenly changes these expectations and the satisfaction equation. Despite uncomplicated surgery, cataract patients may now be dissatisfied because their refractive expectations for uncorrected visual function are not met. Part of the issue is that in an effort to understand confusing concepts such as refractive error, focal point, and depth of focus, many patients tend to oversimplify the value proposition. Since insurance already covers the cataract operation, many patients simply assume that "paying extra for this lens means that I won't need glasses to drive (or read)." The need for effective preoperative counseling to set realistic expectations is widely recognized. For these reasons, it also makes sense that the most common cause of patient dissatisfaction following any refractive IOL procedure is residual refractive error. For instance, while 90% of our patients are within 1.0 D of spherical target, there may only be 75% who are within 0.5 D of target. Emmetropic outcomes are particularly crucial with multifocal IOLs. In two separate studies of unhappy multifocal IOL patients, complaints of blurry vision due to residual refractive error were present in a large percentage of subjects.1,2 In one of these studies, 28% of eyes had residual astigmatism of 0.75 D or greater.1 With a monofocal IOL, 0.5 D of myopia or a small amount of astigmatism is tolerable and may actually increase depth of focus. With diffractive multifocal IOLs, however, the inherent loss of image contrast makes these lenses much less forgiving of the same errors. This is an inevitable lesson that every refractive cataract surgeon learns through experience, but researchers at the University of Rochester demonstrated this in convincing fashion.3 An adaptive optics wavefront sensing system was used to measure through-focus image quality of different presbyopiacorrecting IOLs in a pseudophakic model eye. The advantage of an optical bench simulation is that it separates optical quality from other clinical variables, such as the patient's corneal surface, fovea, and brain. The image quality and depth of focus of both the ReSTOR SN6AD1 (Alcon, Fort Worth, Texas) and the Tecnis ZM900 (Abbott Medical Optics, Santa Ana, Calif.) multifocal IOLs dropped noticeably with more than 0.75 D of corneal astigmatism. In addition, optical performance of the multifocal IOLs was much more sensitive to corneal astigmatism compared to a monofocal IOL. That so many cataract surgeons are unable to perform keratorefractive enhancement surgery on their own patients is a significant problem whose adverse effect on premium refractive IOL adoption rates is difficult to estimate or quantify. Frequent enough failure to attain emmetropia decreases the surgeon's confidence and ability to recommend presbyopia-correcting IOLs for certain patients (e.g., those with preoperative astigmatism or atypically long or short axial length). More importantly, patient dissatisfaction is much higher if expectations for reduced spectacle dependence are not met. This produces negative rather The American Society of Cataract & Refractive Surgery has developed a new series of EyeWorld programs designed to teach cataract surgeons how to perform PRK enhancement of ammetropic pseudophakic eyes. This program was co-chaired by Richard Hoffman, MD, and Dr. Chang. You can read about it in the Tuesday, April 23 edition of EyeWorld Today at daily.eyeworld.org.

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