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Veerendranath Pesala, Sangeetha Srinivasan, Ethan Solomon, Vitor F. Pamplona, Manuel M. Oliveira, Ramesh Raskar, Shrikant Bharadwaj; Comparison of a Novel Cell Phone-Based Refraction Technique (NETRA) With Objective Clinical Retinoscopy. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2852.
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© ARVO (1962-2015); The Authors (2016-present)
Uncorrected refractive errors are the largest cause of avoidable blindness in developing countries. The effectiveness of population-based vision screening programs significantly enhanced if a rapid, cost-effective and quantitative method for estimating the refractive-errors is available. A novel cell-phone based technique (NETRA) has been designed to rapidly quantify the refractive-error status of the eye. This study determined the accuracy and precision of this prototype device in determining spherical refractive error in adults, in comparison to gold-standard objective retinoscopy.
The optical setup of NETRA consists primarily of a pinhole mask and is retrofit on a high-resolution cell phone (Samsung Behold IITM) that displays a spatially resolved pattern of red-green lines to the subject. Refractive error is estimated by subjectively aligning the red-green patterns using a custom-designed user-interface on the cell phone. In this study, cycloplegic spherical refractive errors (SR) of the dominant eye of 29 adults (mean ± SD age: 23.1 ± 2.6yrs), with best-corrected visual acuity of 20/20, were measured thrice using the NETRA and averaged. SE of the same eye was also determined using objective restinoscopy performed by an experienced Optometrist.
Cycloplegic SR of the subjects ranged from -6.25D to +3.00D. The SR determined by NETRA was well correlated with that of objective retinoscopy (r=0.96) and the two measures were not statistically significantly different from each other (p=0.14). Orthogonal linear regression fit to the plot of SR determined by NETRA against those determined by retinoscopy had a slope of 0.86 and a y-intercept of -0.22D. The mean (± 1SD) deviation for the three measures of SR determined by NETRA across all subjects was 0.18 ± 0.15D.
When compared to objective retinoscopy, NETRA slightly underestimated the myopic and hyperopic cycloplegic refractive errors and had a small myopic offset of 0.22D. NETRA estimated myopic and hyperopic refractive errors with a mean precision of 0.18D. These suggest that NETRA could be used as an effective tool for rapidly estimating refractive errors in a vision-screening program. Accuracy of this novel prototype device in estimating refractive errors is expected to increase as technology evolves.
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