EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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February 2012 IOLs February 2011 Determining continued from page 61 for any induced astigmatism. Operating at 90 degrees with an average incision of about 2.5 mm will create an SIA "somewhere around 0.6-0.8," Dr. Holladay said. "But a horizontal 2.5 mm incision induces 0.4-0.6 D in the horizontal meridian, or about 50% less SIA." He added the Holladay IOL Consultant includes an "optimizer" showing the four incision locations where no residual astigmatism will be intro- duced. "Astigmatism goes to visual quality," Dr. Kezirian said. "It be- hooves a surgeon to reduce the amount of SIA." Surgeons who operate on a fixed axis need to perform a vector sub- traction of pre-op and post-op corneal astigmatism and average them, "but they should do a his- togram distribution" as well. If IOLs are placed on axis "the worst that happens is I over- or un- dercorrect, but I still get the full ben- efit of the IOL," Dr. Kezirian said. "But moving the axis 15 degrees de- creases the IOL efficacy by half. If I go 30 degrees, I've negated the bene- fit altogether. That reduces quality of vision because you have two toric surfaces interacting in an oblique axis and it can't be corrected with glasses" (Figure 1). Dr. Hill "never operates in the same place—I move my incision so I'm always on the steep axis," and said those who operate temporally will "always have variability" in their outcomes. "Surgeons who operate tempo- rally are always going to make the horizontal meridian flatter than it was pre-op in the post-op. If that's the case, they're going to change the magnitude of astigmatism as well as the axis," Dr. Holladay said, adding "there are only four possible places to put an incision so there's no residual astigmatism." "We have found that quite a bit of astigmatism on the posterior cornea can really influence out- comes. We're reformulating another toric IOL nomogram based on these data as well," Dr. Koch said. "The thing to remember about SIA is that it's not the same for all eyes," Dr. Hill said. "It's easy to cal- culate a mean value, but difficult to anticipate an exact value for individ- ual patients." EW Whether you're just beginning or experienced in cataract and refractive surgery, ASCRS is the professional society that's right for every stage of your career. Mentors and Innovators As an experienced anterior segment ophthalmologist, you've come to understand the importance of innovation and collaboration. It's through collaboration that ophthalmology improves and expands—at times in great leaps and at times through subtle change. Through its many educational and networking services, ASCRS provides an effective forum for the debate of new ideas and the incremental improvement of technique and outcomes. ASCRS offers the means and the unrestricted opportunity to advance the profession and yourself. Join ASCRS today! The Society for Surgeons AMERICAN SOCIETY OF CATARACT AND REFRACTIVE SURGERY 4000 Legato Road, Suite 700, Fairfax, VA 22033 • 703-591-2220 • www.ASCRS.org Reference 1. Wang L, Dixit L, Weikert MP, Jenkins RB, Koch DD. Incisional healing changes of clear corneal cataract incisions evaluated using Fourier-domain optical coherence tomography. Article in press, J Cataract Refract Surg. Editors' note: Dr. Brass has financial interests with Alcon (Fort Worth, Texas). Dr. Hill has financial interests with Alcon and Haag-Streit (Koeniz, Switzerland). Dr. Holladay is the devel- oper of the Holladay IOL Consultant programs. Dr. Koch has financial inter- ests with Alcon and Abbott Medical Optics (Santa Ana, Calif.). Dr. Wang has no financial interests related to this article. Contact information Brass: 518-782-7827 Hill: 480-981-6130, hill@doctor-hill.com Holladay: holladay@docholladay.com Kezirian: 480-664-1800, guy1000@surgivision.net Koch: 713-798-6443, dkoch@bcm.edu Wang: 713-798-7946, liw@bcm.edu EW FEATURE 63 An ASCRS Membership For every stage of your career