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The effect of pseudophakic ametropia on refractive IOL outcomes, methods for the management of pre-existing astigma- tism intraoperatively and residual refractive errors postoperatively, and ways to incor- porate these methods into practice were the focus of an EyeWorld CME Education program at the 2013 ASCRS•ASOA Symposium & Congress. The impact of refractive error on quality vision and satisfaction levels Refractive errors through the optical bench Bench analyses conducted by Scott M. MacRae, MD, and colleagues at the University of Rochester, N.Y., illustrate the effect of residual refractive error on pseudophakic eyes. Quoting Richard L. Lindstrom, MD, Dr. MacRae, director of refractive services and professor of visual science, University of Rochester, said that "at one to three months, a disproportionate amount of people, about 57.6% of premium IOL users, may not have received the full visual correction. "Multifocals are disproportionately affected," he added. This effect has been documented in previous studies, such as one published by Hayashi and colleagues in the Journal of Cataract & Refractive Surgery (2010). Looking at patients implanted with the ReSTOR 3 and 4 (Alcon, Fort Worth, Texas), Hayashi and colleagues found that "astigmatism up to 1.00 D is tolerated." Dr. MacRae and his colleagues— including Geunyoung Yoon, PhD, Len Zheleznyak, MS, and Jorge Alio, MD— decided to look at this effect in detail using optical bench analysis. The optical bench can be used to simulate the visual system of an eye with any intraocular lens at any degree of refractive error. "We can intro- duce sphere, cylinder, or higher-order aberration and see what happens," said Dr. MacRae. In the optical bench or adaptive-optics IOL metrology system, a letter chart is pro- jected through an artificial pupil and an IOL mounted in a wet cell. A Badal optometer can be used to change the apparent object distance, while a deformable mirror is used to induce corneal aberrations. A CCD sen- sor captures the image of the letter chart after passing through the entire system. In effect, the optical bench allows researchers to simulate the image pro- jected through a lens that hits the patient's retina—essentially, what a patient actually sees, or would see, objectively, subtracting neurological bias. Dr. MacRae and his colleagues found that for eyes that have multifocal IOLs, there is a reduction in depth of focus as you move from 0.5 D to 1.0 D of corneal astigmatism; the depth of focus advantage of multifocal IOLs such as the ReSTOR 3D and the Tecnis Multifocal (Abbott Medical Optics, Santa Ana, Calif.) disappears at 1.0 D, compared with the AcrySof monofo- cal (Alcon), and the Crystalens AO and HD (Bausch + Lomb, Rochester, N.Y.). Corneal astigmatism also decreases image quality, in which case the dispropor- tionate effect on multifocal IOLs is seen as a decrease in image quality significantly worse than in monofocal IOLs by 0.75 D at both distance and near. They also looked at the through-focus image quality curves of four different IOLs: three multifocal IOLs—the FineVision Micro F diffractive trifocal (Physiol, Bel- gium), the Mplus rotationally asymmetric refractive multifocal (Oculentis, Berlin), and the ReSTOR 3D—with the AcrySof monofocal. In all cases, adding astigmatism up to 1.00 D, the image peaks of each lens progressively flattened to match the monofocal lens, graphically illustrating the decrease in image quality. Adding higher-order aberration simi- larly reduced image quality for all these lenses. "If you start adding in some subtle higher-order aberration in addition to astigmatism, image quality can go way down," Dr. MacRae said. "Corneal astigmatism more than about 0.5 D and higher-order aberrations reduce image quality for all multifocals and dispro- portionately affect these patients," he concluded. "It's critical to correct this." To address the problem, Dr. MacRae said he typically "falls back" on mini-PRK in patients with residual astigmatism and higher-order aberrations, in which, he added, the 7-mm treatment zone takes about 30% less epithelium off compared to the 8.5 mm treatment zone. "In these older patients, it's very handy." Residual error and satisfaction Optical bench testing "subtracts the pa- tient's brain" and examines the optical ef- fects of IOLs directly on the visual system. But how does residual refractive error affect outcomes in actual, living patients? Steven C. Schallhorn, MD, medical direc- tor, Optical Express, Glasgow, U.K., and in private practice, San Diego, looked at the 2 Reducing pseudophakic ametropia to drive improved refractive IOL outcomes Decrease in image quality is significantly worse in multifocal IOLs compared to monofocal IOLs by 0.75 D of astigmatism.

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