NEWS & OPINION EWAP MARCH 2023 45 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 Contact information Challa: pratap.challa@duke.edu 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 developed 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 multiple formulas and generates an average recommended IOL power of the included methods. 4 A review by the American Academy of Ophthalmology (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-embedded 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, corrected distance VA of worse than 20/40, or any intraoperative or postoperative complications that would skew final refractive data. All patients underwent preoperative biometry with the IOLMaster 500 or 700 as well as Atlas topography (Carl Zeiss Meditec) and Scheimpflug tomography. All data was entered into the ASCRS online calculator without 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-hyperopic ablation patients for the Barrett True-K No-History, Haigis-L, and Shammas formulas. The authors were able to calculate IOL prediction error This article originally appeared in the December 2022 issue of EyeWorld. It has been slightly modified and appears here with permission from the ASCRS Ophthalmic Services Corp. From left: Sri Meghana Konda, MD, Ellis Wisely, MD, Cason Robbins, MD, James Tian, MD, and Pratap Challa, MD. Source: Duke University
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