Evaluating Refractive Outcomes after Cataract Surgery

Purpose: To compare methods for evaluating refractive outcomes after cataract surgery to detect outliers. Design: Case series database study of the evaluation of diagnostic technology. Participants: Consecutive patients who had uneventful cataract operations over a 5-year period. Methods: The intended and postoperative refractive outcome and differences between these were analyzed as a spherical equivalent, cylinder, and spherocylinder. The average keratometry and differences between steep and flat keratometric meridians were used to calculate the intended refractive error. Main Outcome Measures: Outliers were defined as patients for whom the difference between the intended and postoperative refractive errors was more than 3 standard deviations (SDs) away from the mean. Results: A total of 9000 patients were included. Twelve patients had missing data and were excluded. The mean intended refractive outcome was −0.12+0.12×2 (95% lower confidence limit [LCL], −1.94+1.06×44; 95% upper confidence limit [UCL], +0.77+1.05×140). The actual postoperative refractive error was −0.30+0.47×6 (95% LCL, −2.36+1.31×36; 95% UCL, +1.00+1.18×148) with a difference from the intended of −0.18+0.35×7 (95% LCL, −1.91+1.22×38; 95% UCL, +0.75+1.09×145). Treating the components of the refractive error independently, outliers were observed in 82 eyes (0.91%) based on the sphere, 46 eyes (0.51%) based on the spherical equivalent, 115 eyes (1.28%) based on treating the cylinder as a scalar, and 76 eyes (0.85%) based on treating the cylinder as a vector. When the differences between the intended and postoperative refractive errors were calculated as a compound spherocylinder, outliers were observed for 233 eyes (2.59%). Conclusions: Treating the intended refractive outcome as a spherocylinder improves the precision for detecting clinically significant refractive outliers.