Comparing Refractive Prediction Accuracy in Irregular Corneas: Barrett’s IOL Calculator versus Holladay’s Equivalent Keratometry Readings - 5691
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Author’s Disclosure Block: Jobanpreet Dhillon, none; Kevin Min, none; Marah ElKabouli, none; Annelise Saunders, none; George Mintsioulis, none; Setareh Ziai, none; Mona Koaik, none
Abstract Body
Purpose: Hyperopic outcomes following cataract surgery in irregular corneas, such as those seen in keratoconus (KC) and post-penetrating keratoplasty (PKP) eyes, has been a limiting factor in achieving the best post-operative visual acuity. The purpose of the current work is to determine whether using anterior and posterior keratometry measurements from Holladay’s Equivalent Keratometry Reading (EKR) 65 provides better predictive refractive accuracy than the current Barrett True K and Kane formulas in KC and post-PKP corneas. Methods: Single-center, retrospective chart review of KC and PKP eyes who underwent cataract surgery with monofocal intraocular lens (IOL) implantation between September 2015 to December 2023. Pre-operative keratometry from IOL Master Biometry (IOL Master 700) were applied in Barrett True K and Kane formulas, and EKR measurements from Pentacam Corneal Tomography (Scheimpflug EKR 65 at 4.5 mm) were applied in Barrett Universal II formula to obtain the predicted residual refraction (diopters, D). Primary outcome compared prediction error (PE), which was calculated as the difference between measured post-operative spherical equivalence and predicted residual refraction, and the mean absolute prediction error (MAE) among the three formulas. Results: Twenty-three eyes (16 PKP; 7 KC) from 21 patients (13 males; 8 females) with mean age of 62.9 ± 10.6 years met inclusion criteria. Mean flat and steep keratometry values from IOL Master Biometry were 42.4 ± 3.2 D and 48.4 ± 4.4 D, respectively, and 42.8 ± 2.9 D and 46.8 ± 3.0 D from Holladay’s EKR 65, respectively. Mean PE was 0.52 ± 2.66 for Barrett True K formula, 0.60 ± 2.47 D for Kane formula, and 0.37 ± 2.49 D for Barrett Universal II formula. Mean PE was not significantly different from zero among the three formulas. MAE was lowest in Barrett True K formula (1.48 ± 2.25 D) as compared to Kane formula (1.62 ± 1.93 D) and Barrett Universal II formula (1.68 ± 1.84 D); however, no statistical differences were noted in overall or subgroup (KC, PKP) analyses. Mean best corrected visual acuity significantly improved following cataract surgery (0.36 ± 0.27 logMAR vs. 0.18 ± 0.20 logMAR; p=0.02). Conclusion: These findings suggest that Holladay’s EKR is non-inferior to using IOL Master keratometry data with current IOL formulas in low-moderate astigmatism patients with irregular corneas. Current work is limited by its retrospective nature and small astigmatism of the included eyes that may not fully represent all KC and PKP corneas. Large-scale prospective study is warranted to confirm above trends.