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Hilary Gaiser, Bruce Moore, Vitor Pamplona, Nadine Solaka, David Schafran, Dennis Merrill, Nathaniel Sharpe, Joe Geringer, Ramesh Raskar; Comparison of a Novel Cell Phone-Based Refraction Technique (Netra-G) with Subjective Refraction. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2340.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the performance of a cell phone based refracting device (NETRA-G). This study determines the accuracy of this prototype in determining refractive error in comparison to subjective refraction (SR).
NETRA-G (NET) retrofits a high-resolution mobile phone (Sony Xperia U) by adding a pinhole mask, a film and a lens onto the display. The device is bi-ocular with the fellow eye viewing an object at infinity. The subject aligns red and green lines with the translation on screen proportional to refractive error. 27 subjects (mean + SD age 24.79 +/- 1.60) underwent SR, and NET refraction. Subjects refractive error ranged from plano to -6.0D (mean + SD refraction -3.34 +/- 1.46D). Exclusion criteria included amblyopia, floaters, divergent vertical deviation and any ocular pathology. The NET result was used as a starting point for SR.
For all 27 subjects (54 eyes), the average absolute difference between NET and SR is 0.31 +/- 0.37D. The refraction determined by NET is well correlated with that of SR r=0.96 and the two measures were not statistically significantly different from each other (p=0.36>0.05). Orthogonal linear regression fit presented a slope of 0.92 and a y-intercept of -0.36D. Average difference on visual acuity between SR and NET 0.089 +/- 0.13 logMar and 77% received 20/25 or better vision directly from NET.
When compared to SR, NET slightly overestimated the myopic refractive errors and had a small myopic offset of -0.36D. On average, the visual acuity difference between SR and NET is less then a line on the logMar chart. The results show that NET has potential to be a used as an effective tool for rapidly estimating refractive errors by non-eyecare professionals. Accuracy of this novel technique is expected to increase as technology evolves.
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