Evaluation of the SVOne: A Handheld, Smartphone-Based Autorefractor

Kenneth J Ciuffreda, Mark Rosenfield, Kenneth J Ciuffreda, Mark Rosenfield

Abstract

Purpose: The SVOne is a portable Hartmann-Shack wavefront aberrometer that can be attached to a smartphone to determine the refractive error of the eye objectively. The aim of the present study was to compare the findings of the SVOne with retinoscopy, subjective refraction, and two commercially available autorefractors (Topcon KR-1W and Righton Retinomax-3).

Methods: Refractive error was assessed both with and without cycloplegia in 50 visually normal, young adults using the five techniques described above. Further, to assess repeatability of the instruments, the entire procedure was repeated in a subgroup of 10 subjects. All data were analyzed in terms of power vectors (M, J0, and J45).

Results: No significant difference was observed between the mean values of M (spherical equivalent) for the different techniques. However, a significantly higher mean value of precyclopegic J0 was recorded for the SVOne, which also had the highest limits of agreement for both the J0 and J45 astigmatic components. Retinoscopy and subjective refraction showed the best repeatability (in terms of M values) for precycloplegic and postcycloplegic measurements, respectively. High and significant linear correlations were observed between the subjective findings and the other four techniques.

Conclusions: The results indicate that the SVOne handheld aberrometer provides measurements of refractive error in normal, young individuals that are not significantly different from other subjective and objective procedures. This instrument is valuable for vision screenings, as well as examinations taking place outside the clinical office. It may also serve as an adjunct in the standard optometric examination.

Figures

FIGURE 1
FIGURE 1
The SVOne aberrometer/autorefractor.
FIGURE 2
FIGURE 2
The array of Hartmann-Shack images are clearly visible on the smartphone screen attached to the SVOne. A color version of this figure is available online at www.optvissci.com.
FIGURE 3
FIGURE 3
Plots showing the difference between the SVOne and subjective refraction findings, with respect to the mean of these two results for 50 subjects. A to C show the findings for M, J0, and J45, respectively, without cycloplegia. D to F show the findings for M, J0, and J45, respectively, under cycloplegia. In all figures, the solid line represents the mean difference, whereas the upper and lower dashed lines indicate the 95% LOA (calculated as 1.96 times the SD of the differences).
FIGURE 4
FIGURE 4
Mean values of refractive error measured from a schematic eye using the SVOne after the introduction of spherical trial lenses. An almost perfect linear correlation was observed (r2 = 0.998). The equation of the regression line was y = −1.11x + 0.62.
FIGURE 5
FIGURE 5
Appearance of the smartphone screen when measuring the refractive error of a schematic eye that has been tilted 10 degrees about its horizontal axis. Almost half of the array of Hartmann-Shack images are no longer visible. Accordingly, it is obvious to the operator that the device has been tilted away from the proper alignment. A color version of this figure is available online at www.optvissci.com.

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Source: PubMed

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