Eyeworld

18 | EYEWORLD | DECEMBER 2022 Contact Challa: pratap.challa@duke.edu ASCRS NEWS test the benefit of having a range of values, it may be reassuring to see a range to decrease the risk that any one formula would create an outlier. An outlier analysis was performed on 12 myopic and 6 hyperopic outliers; however, this outlier sample size may be insufficient to reas- sure against seeing a range of calculators. We also noted the that the study included the Barrett True-K in the ASCRS average to which the Barrett True-K was compared with. For future directions, we are interested in the results of a similar analysis in post-RK eyes as well as a comparison with the Barrett True-K Total Keratometry. Conclusion The authors demonstrated that for eyes with previous myopic or hyperopic laser refractive surgery, the Barrett True-K formula built into the biometer was equal or non-inferior to the multiple method approach using the ASCRS online calculator. The advantages of using the Barrett True-K formula built into the biometer include elimination of transcription error risk and reduced time and personnel needed. ASCRS calculator. The accuracy of the Barrett True-K formula for a refractive outcome within 0.50 D of the target is approaching the accuracy reported in the literature for eyes even without a history of refractive surgery. It should be noted that the cataract sur- geries included in the study included different IOL manufacturers and types, as well as dif- ferent surgeons. This is both a weakness and a strength because the results may then be applied to a wider group of surgeons and IOL types. During our Journal Club discussion, res- idents pointed out that additional strengths include the large number of post-hyperopic ablation eyes in the study, 47 eyes from 34 patients, when much of the literature focuses on patients with post-myopic ablations. All patients had both Atlas and Pentacam (Oculus) imaging, thus allowing for more formulas to be used and averaged (only the Galilei [Ziemer] and OCT- based formulas were not used). We noted that by forgoing the ASCRS cal- culator, we lose the range of recommended IOL powers in favor of a single IOL power generated by the Barrett True-K. While there is no way to continued from page 17 IOL power calculations after LASIK or PRK: Barrett True-K biometer-only calculation strategy yields equivalent outcomes as a multiple formula approach Ferguson TJ, et al. J Cataract Refract Surg. 2022;48:784–789 n Purpose: To compare the accuracy of intraocular lens (IOL) power calculations performed using the biometer-embedded Barrett True-K formula versus a multiple formula approach using the ASCRS post- refractive calculator in eyes with prior myopic or hyperopic refractive surgery. n Setting: Cleveland Clinic Cole Eye Institute, Cleveland, Ohio n Design: Retrospective, consecutive case series n Methods: Patients who underwent cataract surgery with a history of corneal refractive surgery were included. For each formula, the IOL prediction error (PE) and refractive PE was calculated. Main outcome measures included mean absolute error (MAE) as well as the percentage of eyes within ±0.25, ±0.50 and ±1.00 diopters (D). n Results: A total of 96 post-myopic eyes and 47 post-hyperopic eyes were analyzed. In the post-myopic cohort, the Barrett True-K had the lowest MAE (0.36 D) followed by the Haigis-L (0.41 D). The Barrett-True K had a significantly higher percentage (44.8%) of eyes within ±0.25 D in comparison to the Haigis-L (34.4%), which had the second highest percentage (P<.01). In the post-hyperopic cohort, the Barrett True-K had the lowest MAE (0.41 D) followed by the ASCRS–mean (0.46). The Barrett True-K and ASCRS–mean had the highest percentage of eyes within ±0.25 D (42.6% vs 38.3%, P=.16). n Conclusions: The Barrett-True K formula built into the biometer performed equivalently to a multiple formula approach on the ASCRS online calculator in both post-myopic and post-hyperopic eyes. This approach reduces the potential for transcription error from data entry for lens power calculation approaches that require manual data entry.

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