Eyeworld

SEPTEMBER 2019 | EYEWORLD | 21 tions to the U.K. cohort also resulted in statis- tically significant improved refractive outcomes for all formulas except the Hoffer Q (while not statistically significant, the trend showed improvement as well). Subsequently, U.K. for- mula-specific coefficients were calculated and compared to the Australian based cohort with similar coefficients for the BUII but slightly dif- ferent coefficients for the remaining formulas. Results for the patient-specific method showed that both cohorts had significant im- provement in the number of second eyes within 0.5 D of PPOR. Overall, both the formula-spe- cific and patient-specific methods improved refinement of the second eye, and there was no significant difference between the two methods. Of note, the formula-specific method appears to be more user friendly. Discussion Today, our patients expect excellent refractive outcomes after cataract surgery. The work by Turnbull and Barrett helps cataract surgeons get closer to meeting their goals by refining second eye outcomes based on first eye results. Their study provides a methodological way for second eye refinement that is applicable to two hetero- geneous populations. There are several novel aspects to be high- lighted. First, this study generates formula-spe- cific adjustment coefficients, whereas previous studies have only offered general adjustment factors. Second, the primary cohort data is validated in a different patient population that was operated on by a heterogeneous group of surgeons, including trainees. Third, the authors regression coefficients based on the PE of the first eye in order to adjust the PPOR of the second eye. Finally, they recalculated the percent of second eyes that were within 0.5 D, 0.75 D, and 1 D of the PPOR. With the patient-specific method, the authors retrospectively calculated ideal IOL constants (IOLc) for BUII and SRK/T in both the first and second eye of each patient. They then derived a universal adjustment coefficient that could be applied to the first eye IOLc to arrive at an idealized second eye IOLc. Next, they recalculated the percent of second eyes that were within 0.5 D, 0.75 D, and 1 D of the PPOR after the adjustment. In short, the formula-specific method gen- erated a unique correction factor based on the IOL formula employed by utilizing the PE of the first eye for the second eye IOL calculation, whereas the patient-specific method generated a correction factor to optimize the IOL con- stant for the second eye based on the optimized IOLc of the first eye. Finally, Turnbull and Barrett tested both validity and accuracy by applying the Austra- lian coefficients from each method to the U.K. cohort and also separately calculating U.K. co- efficients and comparing these to the Australian coefficients. Results The study showed that application of the formula-specific correction to the Australian cohort significantly improved the number of second eyes that were within 0.5 D of the target refraction for all IOL formulas. Application of the Australian based formula-specific correc- continued on page 22 Massachusetts Eye and Ear residents, December 2018 Source: Massachusetts Eye and Ear One question about separate vs. same-day, sequential bilateral surgery is the effect on refractive outcomes when the first eye result is known. I've asked the MEE residents to review this study that is published in the September JCRS. —David F. Chang, MD, EyeWorld Journal Club Editor

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