Eyeworld Daily News

54 | EYEWORLD DAILY NEWS | MAY 17, 2020 DAILY NEWS ASCRS VIRTUAL ANNUAL MEETING of corneal astigmatism, the results were similar to previous findings, and there wasn't a statistical difference between the three groups or the total, he said. But when looking at the magnitude of under and over correction, the study did find a difference that was statistically significant for with- the-rule and against-the rule groups, as well as the total. On average, in cases of residual astigmatism when intraoper- ative aberrometry was used, there was a decrease of 0.12 D of over correction and 0.07 D of under correction. Dr. Kramer did note that there may be lim- itations in the results, adding that the study did not ask how the surgeons used intraopera- tive aberrometry. For these and other similar paper presentations, view SPS- 214. Editors' note: Dr. McKee has financial interests with Carl Zeiss Meditec, Haag-Streit, LENSAR, and Ivantis. Dr. Kramer has no financial interests related to his presentation. over correction of with-the- rule astigmatism. Another important fact was that ante- rior corneal astigmatism tends to drift from with-the-rule to against-the-rule as patients age, he added. Dr. Kramer's study analyzed all the entries made to astigma- tismfix.com from its inception on Sept. 5, 2013, through Dec. 31, 2019 (115,415 total records). "We found 28,791 to represent actual eyes," he said. These were then broken down into groups based on the axis they were intended to be placed (with-the-rule, against- the-rule, or oblique). "As toric IOLs are always placed on the steep meridian of astigmatism, one can extrapolate the type of corneal astigmatism without actually having the Ks entered into the online calculator," Dr. Kramer said. For a limit- ed time, there were optional questions users could answer on astigmatismfix.com to help contribute to this research. One of them was if intraoper- ative aberrometry was used. There were 9,336 entries that answered this question, he said, and about 19% answered "yes." The entire population of this study had at least 0.5 D of residual refractive astigmatism postop. The study found a ten- dency for under correction of against-the-rule astigmatism and a near 50/50 split for with-the-rule astigmatism, Dr. Kramer said. Initially, this may be counterintuitive, he said, as some surgeons may intentionally under correct with-the-rule and over correct against-the-rule astigmatism in anticipation of the against- the-rule drift of the anterior corneal curvature and also to give the patient depth of field. "So, if anything, we anticipat- ed to see the opposite of these findings," he said. So why the unexpected results? "We found our answer when we stratified the data by time," he said. In earlier years, there was much more under correction of against- the-rule and over correction of with-the-rule astigmatism, Dr. Kramer said, which is the case when the power of the posterior cornea is not con- sidered when selecting the cylinder power of the toric IOL. However, as the Baylor toric nomogram and the nomogram by Graham Barrett, MD, be- came more widely used, and now even being able to more accurately measure the curva- ture of the posterior cornea, we are seeing this trend change. As of 2019, Dr. Kramer said there is no difference between the three groups regarding under and over correction of astigmatism, as each group had around 41–42% of over correc- tion. So what about intraop- erative aberrometry? This study only evaluated patients who had residual astigmatism after a toric IOL—the small percentage of patients where things didn't go as planned. So, there very well may have been patients who would have required astigmatismfix.com if the surgeon only used pre- operative measurements, but because they used intraoper- ative aberrometry, they ended up with a more accurate result and didn't have significant residual astigmatism. "We are unable to evaluate that type of scenario with the data we have," he said. When we look at the rates of astigmatism under and over correction based on the type continued from page 53 All live sessions will be made available on the platform for on-demand viewing by May 26, with many sessions available within 24 hours of the meeting. In addition, please enjoy the extensive selection of on-demand papers, skills videos, films, and posters available for viewing at your convenience. Missed a session?

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