Aiming for emmetropia after cataract surgery: Swedish National Cataract Register study

Abstract

To assess and analyze refractive outcome after cataract surgery in Sweden from 2008 through 2010. Swedish cataract surgery units participating in outcome registration of National Cataract Register. Cohort study. Planned and actual postoperative refractions were analyzed for cataract procedures and preoperative and postoperative corneal astigmatism for procedures performed in 2008 though 2010. Induced astigmatism was calculated with Naeser and Behrens polar coordinates. Postoperative refraction was analyzed for 17,056 procedures and corneal astigmatism for 7448 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. Preoperatively, one third of eyes had more than 1.0 D of corneal astigmatism; postoperatively this figure was largely unaltered. The mean induced astigmatism was 0.525 ± 0.804 D in all eyes. 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. No author has a financial or proprietary interest in any material or method mentioned.