Does the Accuracy and Repeatability of Refractive Error Estimates Depend on the Measurement Principle of Autorefractors?

PURPOSE: The purpose of this study was to determine the accuracy and repeatability of refractive errors obtained using three autorefractors based on different measurement principles, vis-à-vis, gold-standard retinoscopy. METHODOLOGY: Accuracy of noncycloplegic, sphero-cylindrical refractive error of 234 eyes was obtained using the rotary prism-based RM-8900 closed-field autorefractor, photorefraction based Spot vision screener, wavefront aberrometry based E-see, and streak retinoscopy by four different examiners, masked to the results of each other. Intersession repeatability of autorefractors was determined by repeat measurements in a subset of 40 subjects. RESULTS: Retinoscopy values of M, J(0), and J(45) power vectors for the cohort ranged from −10.2 to 8 D, −1.4 to 1.8 D, and −0.9 to 1.2 D, respectively. Across autorefractors, the interequipment bias of M and J(0) power vectors were statistically insignificant (< ±0.5 D; P > 0.05) but the corresponding limits of agreement were ±2.5 and ±1 D, respectively, without any trend across instruments or the patient's age (P > 0.5). Repeatability of M and J(0) power vectors were ±0.75 D and ±0.40 D, respectively, across autorefractors. The range of J(45) power vector was too narrow for any meaningful analysis. CONCLUSIONS: Refractive errors measured using autorefractors operating on different principles show minimal bias and good short-term repeatability but relatively large agreement limits, vis-à-vis, retinoscopy. Among them, the wavefront aberrometry based E-see autorefractor performs relatively better in all measurement parameters evaluated here. TRANSLATIONAL RELEVANCE: Although autorefractor estimates of noncycloplegic refractive error appears independent of their measurement principle, their relatively poor agreement with gold-standard retinoscopy warrants caution while used for screening and quantification of refractive errors.