A comparison of a traditional and wavefront autorefraction

To evaluate the agreement between the autorefraction function of the Canon RK-F2, an autorefractor/keratometer based on the ray deflection principle, and the Carl Zeiss Vision i.Profiler(Plus), an wavefront aberrometer, compared with each other and with a noncycloplegic subjective refraction.

Objective refraction results obtained using both instruments were compared with noncycloplegic subjective refractions for 174 eyes of 100 participants. Analysis of sphere, cylinder, and axis using spherical equivalent difference and a new measurement, cross-cylinder difference, was performed. The spherical equivalent refraction and cross-cylinder difference for the manifest refraction were compared using Bland-Altman limits of agreement and 95th percentile analysis.

The 100 participants represent 52 women and 48 men with a mean (±SD) age of 51.7 (±13.8) years, an average (±SD) spherical power of -0.67 (±2.53) diopters (D), and an average (±SD) cylinder power of -0.94 (±0.87) D. The spherical equivalent difference is 0.03 D (Canon) and -0.11 D (Zeiss). The 95% limits of agreement for the spherical equivalent are -0.69 to 0.75 D (Canon) and -0.75 to 0.75 D (Zeiss). The mean cross-cylinder power difference is -0.08 D (Canon) and 0.02 D (Zeiss). The 95% limits of agreement for the cross-cylinder power difference are 0.63 to 0.50 D (Canon) and 0.49 to 0.75 D (Zeiss). The mean axis power difference is -0.04 D (Canon) and 0.05 D (Zeiss). The 95% limits of agreement for axis power difference are -0.71 to 0.63 D (Canon) and -0.78 to 0.78 D (Zeiss). The double-angle astigmatic plot center of distribution for the RK-F2 is 0.035 D at 70 degrees, and that for the i.Profiler(Plus) is 0.053 D at 32 degrees.

Both instruments provided clinically useful spherical equivalent refractive data compared with a subjective refraction, whereas the Canon RK-F2 was slightly more accurate in determining the cylinder power compared with a subjective refraction.