EyeWorld India March 2015 Issue

March 2015 IOL Calculations 27 EWAP SECONDARY FEATURE MORIA S.A. 15, rue Georges Besse 92160 Antony FRANCE Phone: +33 (0) 1 46 74 46 74 - Fax: +33 (0) 1 46 74 46 70 moria@moria-int.com - www.moria-surgical.com THE MORIA OPTION FOR SBK Make your own comparisons between the One Use- Plus and a femtosecond laser in terms of capital investment, disposables per patient, and annual maintenance. www.moria-surgical.com Think Thin Thin, 100-micron, planar flaps Accuracy and predictability equivalent to Femto-SBK Smoother stromal bed No femto-complications … At a fraction of the cost There’s an app for that: toriCAM A nother recent addition to Dr. Barrett’s work is a free app he created for iPhones and iPads called the toriCAM. It provides a way to determine axis of the corneal limbal marks, which is in turn used as a reference to find the correct alignment for a toric IOL during surgery, according to the app description. It can also measure the axis of an implanted IOL at the slit lamp postop. “If you have an accurate reference axis, then your markings are perfect,” Dr. Barrett said. The app, he added, is a “free and simple method” to ensure you have precise measurements. To see an in-depth interview with Dr. Barrett on the app, visit ewreplay.org, search for “Graham Barrett toriCam” or select “ESCRS” from the “Video Archives” dropdown menu, then select “2014” and “Sunday.” Dr. Barrett is featured in the first video that day discussing the app and giving a demonstration of its use. wondered why that is. It’s odd and [does not obey] the rules you would expect from an optical surface,” Dr. Barrett said. “My basic theory is that the normal cornea tends to be elliptical. The diameter is wider in the horizontal meridian. Therefore, that means the curvature of the posterior cornea has to be steeper than the vertical. That means you have against-the-rule astigmatism because the posterior cornea is convex. That also explains why almost all corneas exhibit against- the-rule behavior,” he said. Using that background, Dr. Barrett was able to calculate the diameter of the cornea for each patient as well as the posterior corneal curvature. Looking at the evidence Because the Barrett Toric Calculator is relatively new— it has only been online since the summer of 2013—clinical evidence to support it is just now reaching peer-reviewed journals. In a paper that is in press, Dr. Barrett said his calculator was found to be within half a diopter of residual astigmatism 75% of the time compared with only 33% of the time for the Alcon AcrySof calculator (Fort Worth, Texas) or the Holladay calculator. By adding the Baylor nomogram, the accuracy of the Alcon and Holladay calculators increased to 50%, he said. “The [Barrett Toric] theoretical method is doing significantly better than actually measuring the posterior cornea,” he said. The Barrett Toric Calculator is available on the websites of ASCRS (www.ascrs.org/barrett- toric-calculator) and APACRS (apacrs.org ). The APACRS website also features Dr. Barrett’s True-K formula and Universal II formula. The calculator was also recently built into the LENSTAR LS900 (Haag-Streit, Koeniz, Switzerland). Dr. Barrett encourages surgeons to think carefully about other variables that affect their toric IOL use, such as selecting one primary tool to measure the cornea and then always using secondary tools, a concept he learned from Warren Hill, MD , Mesa, Ariz. “You may have the LENSTAR or other tool for your primary measurement, but you also have to have a secondary tool to confirm your primary is giving you the correct reading,” he said. “Warren uses the analogy of a pilot who doesn’t have just one instrument. The pilot has other instruments to make sure the primary instrument is correct.” EWAP Editors’ note: Dr. Barrett created the Barrett Toric Calculator. Contact information Barrett: graham.barrett@uwa.edu.au