EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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37 EW FEATURE August 2014 Masket) or Modified Masket formula (modified by Dr. Hill) can be useful, said Drs. Masket and Hill. Dr. Masket introduced his formula in the Jour- nal of Cataract & Refractive Surgery in 2006 and has used it for approxi- mately 10 years. 1 Studies and presen- tations that he has done comparing the formula to other calculations have demonstrated its accuracy. For example, in a presentation at the 2013 American Academy of Ophthalmology meeting, he and coauthors Nicole Fram, MD, and Li Wang, MD, compared the Haigis-L formula, the Masket formula, intra- operative aberrometry, and optical coherence tomography (OCT)-based IOL calculation in 38 eyes. All meth- ods led to 70% of eyes being within + or –0.50 D of target. 2 Dr. Masket's formula performed somewhat better, although it was not statistically significant; however he noted that may be because the formula consid- ers previous LVC information. In Dr. Masket's office, when he does not know the previous LVC information, he uses the Haigis-L myopic formula as well as the RTVue (Optovue, Fremont, Calif.) Fourier-domain OCT technology. His office also uses intraoperative aberrometry. "We don't measure corneal power per se. We use meth- ods that bypass the need to measure corneal power," he said. The Shammas and Wang-Koch- Maloney methods are other useful formulas to use if you do not have the patient's LVC history, surgeons said. Maximizing aberrometry and other newer tools Intraoperative aberrometry has allowed surgeons to take into consideration posterior corneal curvature measurements, Dr. Koch said. "It may offer some advantages over measurements depending only on anterior corneal curvature that, frankly, only make a guess at posterior corneal curvature." "The good thing is that intraop- erative aberrometry doesn't rely on changes in corneal power to establish a lens power calculation," Dr. Masket said. Even with aberrometry's advan- tages, it is limited by its estimations of effective lens position—a limita- tion that other IOL formulas face as well. "We need a better way to predict effective lens position, and that's another piece of our whole IOL calculation conundrum," Dr. Koch said. "I think all formulas suffer from determining effective lens position because we can't know in any given eye exactly how far from posterior cornea the lens will sit," Dr. Masket said. The RTVue, with its real-time eye tracking OCT, has helped make post-LVC IOL calculations easier for Dr. Koch as well. "Those numbers are among the best we've got," Dr. Koch said. He uses that along with the GALILEI Dual Scheimpflug Analyzer (Ziemer, Port, Switzerland), the latter of which offers a 3D analysis of the anterior segment. Dr. Koch said they are both help- ful because they measure posterior corneal curvature. "If we can get that value more accurate, I think the whole level of accuracy for IOL cal- culations will improve," he said. EW References 1. Masket S, Masket SE. Simple regression formula for intraocular lens power adjust- ment in eyes requiring cataract surgery after excimer laser photoablation. J Cataract Refract Surg. 2006;32:430–434. 2. Masket S, Fram N, Wang L. Comparison of IOL power calculations in post-LASIK eyes undergoing cataract surgery using multiple formulae, optic coherence tomography (OCT), and intraoperative aberrometry. Presented at the 2013 American Academy of Ophthalmology Annual Meeting, New Orleans. 3. Wang L, Hill WE, Koch DD. Evaluation of intraocular lens power prediction methods using the American Society of Cataract and Refractive Surgery Post-Keratorefractive Intraocular Lens Power Calculator. J Cataract Refract Surg. 2010;36: 1466–1473. Editors' note: Dr. Hill has financial interests with Alcon (Fort Worth, Texas). Dr. Koch has financial interests with Alcon, Abbott Medical Optics (Santa Ana, Calif.), and Ziemer. Dr. Masket has financial interests with Alcon and Haag-Streit (Mason, Ohio). Dr. Packer has financial interests with WaveTec Vision. Contact information Hill: hill@doctor-hill.com Koch: dkoch@bcm.tmc.edu Masket: avcmasket@aol.com Packer: mark@markpackerconsulting.com OASIS name and logo are registered trademarks of OASIS Medical, Inc. 514 S. Vermont Ave, Glendora, CA 91741. LIT-IEFTH-AD-Rev1_7.14 800-528-9786 (USA Toll Free) 909-305-5400 oasis@oasismedical.com www.oasismedical.com Find out more about how we can help your practice. Contact OASIS ® for a surgical demonstration. More than expected - Jeffrey Whitman, M.D. "Just did a case of microophthalmia (17.6mm long) with 16D of hyperopia and dense cataract with small pupil with synechia. Used the OASIS Iris Expander— great case. Planning on editing the video to put up online. " - Adelaide Priester, D.O. 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