Eyeworld

22 | EYEWORLD | SEPTEMBER 2019 the audience to understand how the second-eye refinement, which may have been utilized in the U.K. series, potentially affects the mean abso- lute error (MAE). The BUII formula outperforms the other three formulas (in both Australian and U.K. cohorts), even without any correction factor. The third generation vergence formulas such as Hoffer Q, Holladay, and SRK/T, are still widely used by cataract surgeons around the world. However, the result of this study is consistent with the consensus that the latest formulas (the Ladas Super Formula, the Barrett Universal II, and the Hill-RBF) outperform the third and fourth generation formulas regardless of axial length. 7,8 Furthermore, in the BUII formu- la-specific correction, the number of patients within 0.5 D of target increased by 2.16% and 1.99% in the Australian and U.K. cohorts, re- spectively. Thus, there is opportunity for further improvement even in the formulas with the best outcomes. We wonder if the 90% mark may be surpassed in the short future since the artificial intelligence model (Hill-RBF 9 ) continually im- proves its prediction algorithms as the database expands over time. provide a criteria dependent guideline that is simple to follow and can be implemented by any surgeon who aims to adjust their IOL choice for cataract surgery in the second eye. The methods are quite robust given the size of the cohorts and number of formulas evalu- ated. However, if the validation was performed in another single-surgeon cohort, the improve- ment in the second eye PE may have been even larger. Furthermore, subgroup analysis to sepa- rate more symmetric eyes from less symmetric eyes may corroborate the specific recommen- dations from the authors regarding the axial length and cornea power differences. The authors obviously have done an enormous amount of data processing and analysis for this study. However, for the general audience, who may be less familiar with this type of analysis as compared to the experi- enced authors, it would be helpful to provide a hypothetical example, describing step by step how the adjustment coefficient was generated. For example, was the surgeon-intended refrac- tive outcome (rather than the formula-predict- ed refractive outcome) utilized in any of the calculations? Such examples would also help continued from page 21 Using the first eye prediction error in cataract surgery to refine the refractive outcome of the second eye Andrew Turnbull, FRCOphth, Graham Barrett, MD J Cataract Refract Surg. 2019;45(9):1239–1245. to the second eye calculation. The same adjustments were applied to a dataset of 605 U.K. patients, to test the validity of the Australian results. n Results: Australian-derived adjustment coefficients based on PE ranged from 0.30 to 0.56 (BUII 0.30; Hoffer Q 0.56; Holladay I 0.53; SRK/T 0.48). Applying these to the U.K. dataset led to the percentage of patients within 0.50 D of PPOR with their second eye improving from 70.74%, 65.29%, 69.09%, 67.77%, with BUII, Hoffer Q, Holladay I, and SRK/T respectively, to 72.73%, 68.76%, 71.57%, and 72.56%. Using patient-specific optimized IOL constants derived from the first eye had similar efficacy to formula-specific adjustment. n Conclusions: Second-eye refinement via either formula-specific PPOR adjustment or patient-specific IOL constant adjustment improves the percentage of patients achieving the refractive target with their second eye. n Purpose: To refine the refractive outcome of the second eye following cataract surgery, by deriving adjustment coefficients for intraocular lens selection based on the prediction error (PE) of the first eye. n Setting: University Hospital Southampton, Southampton, U.K.; Lions Eye Institute, Perth, Australia n Design: Retrospective study of two heterogeneous datasets n Methods: 139 patients who underwent delayed sequential bilateral cataract surgery (DSBCS) in Australia were retrospectively analyzed. PE was determined by comparing postoperative subjective refraction with the predicted postoperative refraction (PPOR) calculated by the Barrett Universal II (BUII), Hoffer Q, Holladay I, and SRK/T formulae. Adjustment coefficients were derived for each formula and applied to the second eye's IOL calculation. Separately, patient-specific optimized IOL constants were derived from the first eye PE and applied References 1. Narváez J, et al. Accuracy of intraocular lens power prediction using the Hoffer Q, Holladay 1, Holladay 2, and SRK/T formulas. J Cataract Refract Surg. 2006;32:2050–3. 2. Greenstein S, Pineda R. The quest for spectacle indepen- dence: A comparison of multifocal intraocular lens implants and pseudophakic monovision for patients with presbyopia. Semin Ophthalmol. 2017;32:111–115. 3. Melles RB, et al. Accuracy of intraocular lens calculation formulas. Ophthalmology. 2018;125:169–178. 4. Covert DJ, et al. Intraocular lens power selection in the sec- ond eye of patients undergoing bilateral, sequential cataract extraction. Ophthalmology. 2010;117:49–54. 5. Aristodemou P, et al. First eye prediction error improves second eye refractive outcome: results in 2129 patients after bilateral sequential cataract surgery. Oph- thalmology. 2011;118:1701–9. 6. National Institute for Health and Care Excellence. Cataracts in adults: management. NICE Guide- line (NG77). October 2017. 7. Roberts TV, et al. Comparison of Hill-radial basis function, Barrett Universal and current third gener- ation formulas for the calculation of intraocular lens power during cataract surgery. Clin Exp Oph- thalmol. 2018;46:240–246. 8. Kent C. In Search of the Perfect IOL Formula. Review of Ophthal- mology. January 2017. 9. ASCRS Announces Hill-RBF Calculator for Cataract Surgery IOL Power Calculations. ascrs. org/about-ascrs/news-about/ ascrs-announces-hill-rbf-calcu- lator-cataract-surgery-iol-pow- er-calculations. Updated June 2, 2016. Accessed July 31, 2019. 10. McNamara P, et al. Refractive stability following uncomplicated cataract surgery. Clin Exp Optom. 2019;102:154–159. ASCRS NEWS

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