Clinical evaluation of the Shin-Nippon NVision-K 5001/Grand Seiko WR-5100K autorefractor

Purpose. A clinical evaluation of the Shin-Nippon NVision-K 5001 (also branded as the Grand Seiko WR-5100K) autorefractor (Japan) was performed to examine validity and repeatability compared with subjective refraction and Javal-Schiotz keratometry. Methods. Measurements of refractive error were performed on 198 eyes of 99 subjects (aged 23.2 +/- 7.4 years) subjectively (noncycloplegic) by one masked optometrist and objectively with the NVision-K autorefractor by a second optometrist. Keratometry measurements using the NVision-K were compared with the Javal-Schiotz keratometer. Intrasession repeatability of the NVision-K was also assessed on all 99 subjects together with intersession repeatability on a separate occasion separated by 7 to 14 days. Results. Refractive error as measured by the NVision-K was found to be similar (p = 0.67) to subjective refraction (difference, 0.14 +/- 0.35 D). It was both accurate and repeatable over a wide prescription range (-8.25 to +7.25 D). Keratometry as measured by the NVision-K was found to be similar (p > 0.50) to the Javal-Schiotz technique in both the horizontal and vertical meridians (horizontal: difference, 0.02 +/- 0.09 mm; vertical: difference, 0.01 +/- 0.14 mm). There was minimal bias, and the results were repeatable (horizontal: intersession difference, 0.00 +/- 0.09 mm; vertical: intersession difference, -0.01 +/- 0.12 mm). Conclusion. The open-view arrangement of the Shin-Nippon NVision-K 5001 facilitates the measurement of static refractive error and the accommodative response to real-world stimuli. Coupled with its accuracy, repeatability, and capability to measure corneal curvature, it is a valuable addition to objective instrumentation currently available to the optometrist and researcher.