EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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EW CATARACT 42 October 2014 by Ellen Stodola EyeWorld Staff Writer Assessing corneal astigmatism Multiple tools needed to identify astigmatism E lizabeth Yeu, MD, Norfolk, Va., prepared a presentation on "Assess- ing Corneal Astigmatism: What's Important and What's the Best Technology?" which was discussed in the Cataract Dilemmas symposium at the 2014 ASCRS•ASOA Symposium & Congress. Although she was unable to present on this topic at the meeting, Dr. Yeu commented on the major take-home points of her presentation. She also discussed the results from audience surveys on what they are using to treat corneal astigmatism in their practice. Audience results Audience members were asked whether they are using IOLMaster (Carl Zeiss Meditec, Jena, Germany) readings, manual Ks, topography, or a combination of the 3 to treat corneal astigmatism. Of the 124 re- sponses, nearly 75% indicated they are using a combination of these to treat corneal astigmatism. Mean- while, about 14.5% said they are using just IOLMaster readings, about 3% are using manual Ks, and about 8% are using topography. Dr. Yeu said these results sur- prised her, but she is happy to see them. "The question that I'd really like to know is how many people are actually treating astigmatism," she said. "In terms of astigmatism treatment, it's become much more widely utilized now that it is more accurate with toric IOLs and fem- tosecond laser-assisted cataract surgery, as well as a necessity to add corneal relaxing incisions with certain presbyopia-correcting IOLs," she said. She said it seems that more people are purchasing the necessary equipment to do corneal astigma- tism correction. Additionally, Dr. Yeu would like to know the breakdown of those indicating that they are using a combination of the 3 technologies to know if all 3 are being used or if it is a combination of 2. "But if they're using at least 2 different devices, that's great, as long as they are 2 trusted devices and the values correlate well with each other," she said. What is your answer? Dr. Yeu said that she use a combi- nation of treatments: IOLMaster readings, manual Ks, and topogra- phy. But generally speaking, she uses the LENSTAR (Haag-Strait, Mason, Ohio) over the IOLMaster because the measurements tend to be more accurate. "We use a Placido disc image- based photography," Dr. Yeu said. She also has a Humphrey Atlas (Carl Zeiss Meditec), as well as a Nidek OPD (Nidek, Fremont, Calif.). "If there's a huge discrepancy or if it's more difficult to get the patient up to the slit lamp, or for ectasia pa- tients, I'll get manual Ks, too," she said. What does the audience response mean? Dr. Yeu believes the response from the audience indicates a shift in the trend of how anterior corneal astig- matism is treated. When speaking with a variety of doctors in other practices and those completing cornea fellowships, the general con- sensus is that it would be somewhat absurd to not have multiple tools to identify astigmatism, she said. It is important to have a system of checks and balances in case the first device is wrong. It is interesting to see how quickly practice patterns have changed, as even 6 or 7 years ago a lot of practices did not have these devices and some did not even have optical biometry, she said. Many did not own a topogra- phy machine. Topography is useful in a number of ways, Dr. Yeu said. It not only provides the magnitude and actual axis of astigmatism, it also gives a broad picture of whether the astigmatism is normal. This is hard to gauge without a broad axial map and cannot be assessed using just optical biometry and manual Ks. The topographer can also locate subtle irregularities, dry eye, ABMD, and Salzmann's. "I think this is somewhat more of a shift, and people are realizing the value of having more than one form of technology to measure the anterior corneal astigmatism," she said. Presentation Dr. Yeu's presentation on assessing corneal astigmatism highlighted 6 main pearls. The first pearl is to o - tain accurate assessment of anterior corneal astigmatism using both axis and magnitude. The second reminds surgeons that the posterior cornea plays a significant role in total refractive astigmatism. The third encourages the sur- geon to understand the astigmatic effects of corneal incisions being made. The fourth is that anterior cor- neal astigmatism changes over time, and this needs to be considered in the patient's postoperative astig- matic target, specifically to consider whether or not to aim for residual with-the-rule astigmatism. The fifth is that oblique astigmatism is likely with-the-rule astigmatism that is marching toward against-the-rule. The final pearl is that effective lens position can affect the true toricity power in the eye. The key message is that to truly be a refractive cataract surgeon and to be able to manage corneal astig- matism, you have to know certain things about yourself as a surgeon, and it does take some care and thought to it, Dr. Yeu said. Under- standing how to assess astigmatism and having the appropriate devices is one point. "But knowing what your true target is for patients' astigmatic con- trol, their age, as well as the effects of the posterior cornea all play into it," she said. Once you do more astigmatism cases, it's easier to plan for it. "With more experience comes greater ease of use." EW Editors' note: Dr. Yeu has financial interests with Abbott Medical Optics (Santa Ana, Calif.), Alcon (Fort Worth, Texas), and Bausch + Lomb (Bridgewater, N.J.). Contact information Yeu: eyeulin@gmail.com Results of the audience survey on what they are using to treat corneal astigmatism in their practice. Source: ASCRS