Evaluation of an Automated Subjective Refractor

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Purpose.To test the validity and repeatability of an automated subjective refractor compared with subjective refraction performed by clinicians. Corrected visual acuity was used to compare the validity of each technique.Methods.On each of two visits separated by at least 1 week, the following were measured in 60 naive subjects (mean age, 33 ± 11 years): automated objective refraction (AOR) and automated subjective refraction (ASR) with the Topcon BV-1000, subjective refraction by one of two doctors (DR), and monocular visual acuity with the ASR and DR findings. Repeatability of refraction was calculated as the 95% limits of agreement (LoA) between same-mode measurements from the two visits. The validity of the ASR compared with DR was determined two ways: as the 95% LoA between the two measures and as the mean visual acuity measured with each prescription.Results.The DR and AOR had similar repeatability: 95% LoA = −0.49 to +0.46 D and −0.51 to +0.45 D, respectively. The ASR had poorer repeatability with 95% LoA of −0.70 to + 0.71 D. Because of a calibration (offset) error in the right eye path of the BV-1000, the ASR of the right eye yielded refractions +0.26 ± 0.41 D higher than the DR. For the right eye, visual acuity was 3.42 ± 6.09 letters better with the DR than with the ASR, consistent with this calibration error. For the left eye, visual acuity was 1.20 ± 5.20 letters better for the DR.Conclusions.Doctor-performed refractions are more valid and repeatable than the ASR performed with the BV-1000, although the differences are small. When calibrated, the BV-1000 gives similar visual acuity values to the DR, although the visual acuity for the DR is more repeatable.

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