Petros Aristodemou1, John M Sparrow2, Stephen Kaye3. 1. Department of Public Health and Social Medicine, University of Bristol, Bristol, United Kingdom. 2. Department of Public Health and Social Medicine, University of Bristol, Bristol, United Kingdom; Bristol Eye Hospital, Bristol, United Kingdom. 3. Royal Liverpool University Hospital, Liverpool, United Kingdom. Electronic address: s.b.kaye@liverpool.ac.uk.
Abstract
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.
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.
Authors: Chung Shen Chean; Boon Kang Aw Yong; Samuel Comely; Deena Maleedy; Stephen Kaye; Mark Batterbury; Vito Romano; Esmaeil Arbabi; Victor Hu Journal: BMJ Open Ophthalmol Date: 2019-04-09