Eyeworld

16 | EYEWORLD | DECEMBER 2022 by James Tian, MD, Esteban Peralta, MD, Katherine Peters, MD, Sri Meghana Konda, MD, Cason Robbins, MD, C. Ellis Wisely MD, and Pratap Challa, MD corrected distance VA of worse than 20/40, or any intraoperative or postoperative complica- tions that would skew final refractive data. All patients underwent preoperative bi- ometry with the IOLMaster 500 or 700 as well as Atlas topography (Carl Zeiss Meditec) and Scheimpflug tomography. All data was en- tered into the ASCRS online calculator with- out historical data. The ASCRS calculator for post-myopic ablation outputs the recommended IOL power for the Barrett True-K No-History, Wang-Koch-Maloney, Shammas, Haigis-L, and Potvin-Hill Pentacam formulas, as well as an average IOL power from these formulas. The calculator uses the same process for post-hy- peropic ablation patients for the Barrett True-K No-History, Haigis-L, and Shammas formulas. The authors were able to calculate IOL prediction error by setting the actual postop refraction to the target refraction in the Barrett True-K and ASCRS calculators. Those calcula- tors were used to calculate the predicted IOL power, and the difference between the predicted IOL power and the actual implanted IOL power was the IOL prediction error. The IOL predic- tion error was multiplied by 0.7 to estimate the refractive error at the spectacle plane since the ASCRS calculator does not provide an expected refraction for a given lens recommendation. Results In the post-myopic ablation group of 96 eyes of 81 patients, the mean IOL prediction errors were analyzed by a one-sample t-test for each formula to assess whether the error was sta- tistically different from 0 (plano). The Barrett True-K, ASCRS calculator average, and Haigis-L did not have an IOL prediction error statistically different from 0, while the other calculators did. In the post-hyperopic group of 47 eyes from 34 patients, similarly, the Barrett True-K and ASCRS calculator average were not statistically different from 0. The mean refractive prediction error as well as the mean and median absolute refractive pre- EYEWORLD JOURNAL CLUB ASCRS NEWS Review of "IOL power calculations after LASIK or PRK: Barrett True-K biometer- only calculation strategy yields equivalent outcomes as a multiple formula approach" A ccurate IOL calculation in eyes with a history of refractive surgery is challenging but important, especially given the high patient expectations in this population. 1,2 Alongside intraoperative aberrometry and ray tracing technology, multiple formulas have been devel- oped to account for the change in refractive and anatomic assumptions after ablative refractive surgery with no single formula demonstrating proven superior efficacy. 3 This has led to the development of an ASCRS web-based tool that facilitates the simultaneous calculation of mul- tiple formulas and generates an average recom- mended IOL power of the included methods. 4 A review by the American Academy of Oph- thalmology (AAO) of 11 studies found that the ASCRS calculator average provided the lowest residual refractive errors among all methods. 5 However, downsides of using the web-based ASCRS calculator are the time and potential transcription error when manually transcribing data. Meanwhile, the Barrett True-K has been shown to be one of the most accurate methods for post-refractive eyes. 6,7 It is integrated into the IOLMaster 700 (Carl Zeiss Meditec) and Lenstar 900 (Haag-Streit), which eliminates the need for manual data entry into the web-based ASCRS calculator. In order to test whether manual transcription into the ASCRS calculator is necessary, the authors sought to compare the accuracy of the Barrett True-K biometer-embed- ded formula alone versus the other no-history formulas used in the ASCRS online calculator in a series of post-myopic and post-hyperopic ablation eyes. Methods The authors did a retrospective chart review of all cases of cataract surgery performed in patients with a history of myopic or hyperopic laser ablation performed in a single calendar year at their institutions. A variety of lenses and surgeons were included. Patients were excluded if they had a history of RK, incomplete data, Pratap Challa, MD Residency Program Director Department of Ophthalmology Duke University Durham, North Carolina

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