PowerRefractor versus Canon R-50 Autorefraction to assess refractive error in children: a community-based study in Ecuador

Abstract: Purpose. To compare the agreement of the PowerRefractor with Canon R-50 autorefraction for measuring refractive error in a community of Ecuadorian children. Methods. We examined 1564 children aged 5 to 6 years from two ethnically and geographically similar regions of the Ecuadorian highlands. Results of a refraction obtained without cycloplegia with the PowerRefractor and with the Canon R-50 autorefractor (NCAR) were compared with the gold-standard examination, cycloplegic autorefraction (CAR) with the Canon R-50 autorefractor. Power vectors were used to analyze refractive error. Bland-Altman limits of agreement were obtained. Results. Although the mean difference in the spherical equivalent refractive error between the PowerRefractor and CAR was small (-0.03 D +/- 0.05 D), the 95% limits of agreement were wide (+/- 2.03 D). On the other hand, NCAR showed a greater bias (0.97 D +/- 0.04 D) and smaller limits of agreement (+/- 1.49 D). The limits of agreement of the PowerRefractor were also wider than NCAR for measuring astigmatism. When the mean difference was stratified by the subgroups of refractive error vectors, the PowerRefractor was found to have poorer limits of agreement than NCAR for hyperopic defects. Conclusion. The PowerRefractor is accurate, but not as precise for measuring refractive error as compared to the Canon R-50 autorefractor, especially for high hyperopia.