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Martha P. Lang, Helena M. Pakter, Lisia B. Ferreira, Ankit Mohan, Ramesh Raskar, Vitor F. Pamplona, Manoel M. Oliveira; Comparison of a Cell Phone-Based Refraction Technique (NETRA) With Auto-Refraction. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3596.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the subjective refraction results of a novel portable device NETRA (Near Eye Tool for Refractive Assessment) to the measurements of a standard auto-refractor in determining refractive error in adults.
The optical setup of NETRA consists primarily of a pinhole mask that retrofits a cell phone into a measurement tool. The display shows spatially resolved pre-warped patterns 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. For this cross-sectional study, 27 patients were examined from May to August 2011 at Hospital Nossa Senhora da Conceição, Porto Alegre, Brazil. Refractive data were estimated by NETRA and by a standard auto-refractor (Topcon RM8800). After a complete eye examination, patients underwent static and dynamics auto-refraction. For each method of refraction, the spherical equivalent of the refractive correction was calculated by adding one half the cylindrical correction to the spherical correction.
Twenty-three patients (38 eyes) underwent static and twenty-seven patients (50 eyes) dynamic refractive assessment. The age ranged from 14 to 61 years (34.2 ± 13.0 yo) and visual acuity at least 20/40. There was no significant difference between NETRA and auto-refraction under cycloplegia with mean absolute difference of 0.94 ± 0.7 diopters (p = 0.99). For dynamic refraction, the mean absolute difference of spherical equivalent was 2.88 ± 1.8 diopters (p=0.02).
This study demonstrated good agreement of NETRA with the standard method of auto-refraction in patients under cycloplegia. NETRA could measure cycloplegic subjective refraction within a 1 diopter of spherical equivalent difference from auto-refraction. Due to accommodation, NETRA lacks precision in determining refractive errors in dynamic examination. With properly assessment of this accommodation issues, NETRA has good potential of becoming an alternative inexpensive, simple and portable tool for assessment of refractors errors.
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