Validation of Near Eye Tool for Refractive Assessment (NETRA) – Pilot Study

Abstract

Background: Uncorrected-refractive-error (URE) is the leading cause of global vision impairment (VI); 122.5 million people are estimated VI from URE. NETRA is a $30USD clip-on application for smartphones. Purpose: To validate the NETRA as an alternative to subjective refraction for potential use in resource-poor countries. Methods: NETRA uses a pinhole mask attached to a smartphone displaying a spatially resolved pattern to the subject. Refractive error is estimated by the patient subjectively aligning patterns by a touchscreen interface on the smartphone. NETRA was compared to subjective refraction in 34 eyes. Results: The mean Subjective Spherical Equivalent (SSE) was -0.65D (std 2.79, 95%CI ±0.97) Two-sided T-test showed that mean SSE is not statistically significantly different (two sided t-test; t=1.6742 p=0.1036, 95% CI±0.29) from the mean NETRA Spherical Equivalent (NSE) . Mean difference of Spherical Equivalents (NSE -SSE) was 0.24D (Std 0.84, 95%CI ±0.29). And NETRA produced a mean VA improvement of 0.44LogMAR (Std 0.52, 95%CI±0.18), or four Snellen lines. Conclusion: In settings where access to a trained refractionist is not possible, NETRA has the potential to estimate refractive error closely enough to render an individual no longer VI from URE. NETRA is potentially a cost-effective tool in meeting the VISION2020 goals to eradicate avoidable blindness and warrants further testing in resource-poor settings.