Comparison of refractive error measurements in adults with Z-View aberrometer, Humphrey autorefractor, and subjective refraction

BackgroundThe aim of this study was to evaluate whether measurements obtained with the Ophthonix Z-View aberrometer (Vista, California) and a Humphrey autorefractor (Zeiss Humphrey, Dublin, California) correlate with standard subjective refraction measurements, based on visual acuity results.MethodsA retrospective data analysis was completed for 97 patients, age range 18 to 66 years, without evidence of systemic or ocular disease. All data were collected without dilation or cycloplegia. Refractive correction measurements (sphere, cylinder, axis) were converted to power vectors for analysis.ResultsDifferences-versus-means plots show generally excellent agreement between the results of each instrument and subjective refraction, all r2 > 0.77, with the Z-View consistently exhibiting less variability than the autorefractor (AR). Nonetheless, the Z-View tends to undercorrect myopia, whereas the AR tends to overcorrect myopia, with statistically significant mean differences (±SD) in spherical equivalents with respect to subjective refraction of 0.118 (±0.311) and −0.193 (±0.474) diopters (D), respectively. Both instruments tend to overcorrect astigmatism of less than −1.25 and −0.75 D, respectively, in some cases by as much as −0.87 D. Both instruments also tend to err in cylinder axis measurement for low astigmatism, often by more than 10°.ConclusionsThe Ophthonix Z-View aberrometer is a useful objective clinical instrument that provides better accuracy than an AR, and its results can be used as a good starting point for a subjective refraction for most patients. It also measures higher-order aberrations not identified by other techniques. However, as with AR results, a spectacle prescription based solely on its measurements may not be appropriate for all patients.