EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/76185
52 EW RESIDENTS July 2012 EyeWorld journal club Emmetropia after cataract surgery by Matthew Emanuel, M.D., Lawson Grumbine, M.D., Neal Palejwala, M.D., David Risner, M.D., Gagan Sawhney, M.D., Harpreet Walia, M.D., Paul Pruett, M.D. Paul Pruett, M.D., residency program director I invited the Emory residents to review this large retrospective study from the Swedish National Cataract Registry for this month's "EyeWorld journal club." David F. Chang, M.D., chief medical editor Patient goals and expectations of cataract surgery have changed dra- matically with the advancement of IOLs. While post-op spectacle correction was at one time both expected and necessary, emmetropia or specific refractive targets have become the norm. To this end, multiple tools and formulas have been developed to achieve desired refractive outcomes. In the July issue of the Journal of Cataract & Refractive Surgery, Behndig et al. authored "Aiming for em- metropia after cataract surgery: Swedish National Cataract Register study," a retrospective study to assess planned and achieved out- comes after cataract surgery. The authors reviewed 17,056 charts from Sweden's National Cataract Register (NCR) from 2008-2010, which in- cludes all cataract extractions per- formed each year during the month of March. This registry comprises approximately 65% of surgical units in Sweden. Multiple variables were Aiming for emmetropia after cataract surgery: Swedish National Cataract Register study Anders Behndig, M.D., Ph.D., Per Montan, M.D., Ph.D., Ulf Stenevi, M.D., Ph.D., Maria Kugelberg, M.D., Ph.D., Charlotta Zetterström, M.D., Ph.D., Mats Lundström, M.D., Ph.D. J Cataract Refract Surg. (July) 2012; 38: 1181-1186 Purpose: To assess and analyze refractive outcomes after cataract surgery in Sweden from 2008 though 2010. Setting: Swedish cataract surgery units participating in outcome registration of National Cataract Register. Design: Cohort study. Methods: Planned and actual post-operative refractions were analyzed for cataract procedures and pre-operative and post-operative corneal astigmatism for procedures performed in 2008 though 2010. Induced astigmatism was calculated with Naeser and Behrens polar coordinates. Results: Post-operative refraction was analyzed for 17,056 procedures and corneal astigmatism for 7,448 procedures. Emmetropia was targeted in 78.1% of eyes and achieved in 52.7%; 43.0% had less than 1.00 diopter (D) of astigmatism. "Reading myopia" of −3.5 to −1.6 D was targeted in 7.0% of eyes and achieved in 7.8%. Planned hyperopia greater than 1.0 D or myopia greater than −3.5 D was rare. The mean absolute biometry prediction error was 0.402 D±0.338 (SD) in all eyes; however, astigmatic eyes and eyes planned for myopia or hyperopia had higher biometry prediction errors. Younger patients were more often astigmatic and planned for a more myopic outcome. Pre-operatively, one third of eyes had more than 1.0 D of corneal astigmatism; post-operatively this figure was largely unaltered. The mean induced astigmatism was 0.525±0.804 D in all eyes. Conclusions: Emmetropia (spherical equivalent −0.5 to +0.5 D and <1.0 D astigmatism) is the goal in most cataract cases but was reached in only 55% of eyes planned for emmetropia. Factors precluding emmetropia included remaining corneal astigmatism and biometry prediction errors in astigmatic and ametropic eyes. Financial disclosure: No author has a financial or proprietary interest in any material or method mentioned. Source: Getty Images evaluated for association with refrac- tive outcome: planned refraction, refraction in the fellow eye, pre-op astigmatism, first or second eye pro- cedure, age of the patient, and year of surgery. The aim of this study was to analyze planned and achieved refractive outcomes after cataract surgery. Emmetropia was defined as spherical equivalent from −0.50 to +0.50 D, slight myopia as −0.50 to −1.50 D, reading myopia as −1.60 to −3.50 D, and slight hyperopia as +0.50 to +1.00 D. Emmetropia was planned in 78.1% of cases and achieved in 52.7%. Approximately one-third of patients (33.9%) had a final refrac- tion of slight myopia or slight hyperopia, although this was only planned in 11.3% of cases. Seventy- one percent were within 0.50 D of the target value, and greater than 90% were within 1.00 D. Significant hyperopia (>+1.00 D) or myopia (<–3.50 D) was infrequently planned but did occur more often than ex- pected (~5%). The average absolute error from predicted values was 0.402±0.388 D. When compared by year, 2010 was found to have statis- tically lower absolute biometric error than 2009 or 2008, but the authors did not explore these findings further. Also, slightly myopic or hyperopic eyes had a higher deviation from predicted biometry than emmetropic eyes. Pre-op keratometry values were only available for 7,448 cases (44%). Approximately 30% of patients had pre-op corneal astigmatism of at least 1.00 D, and this remained essentially unchanged post-op; eyes with higher pre-op astigmatism con- tinued to have higher astigmatism post-op. Of the 2,676 eyes with greater than 1.00 D of pre-op corneal astigmatism, astigmatic error was reduced in 48%, unaltered in 36%, and increased in 16%. Mean induced astigmatism in the whole sample was less than 0.5 D (0.422±0.544 D). Not surprisingly,