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Accuracy of a Smartphone-based Autorefractor Compared with Criterion-standard Refraction

Jeganathan, V. Swetha E., MPhil(Ophthal)1; Valikodath, Nita, MD, MS1; Niziol, Leslie M., MS1; Hansen, Sean, MD1; Apostolou, Hannah, BS1; Woodward, Maria A., MD, MSc1,2*

doi: 10.1097/OPX.0000000000001308

SIGNIFICANCE Uncorrected refractive error is a prevalent problem throughout the world especially among the low-income population who have limited access to professional eye care and cannot afford eyeglasses.

PURPOSE The purpose of this study was to evaluate the accuracy and usability of a low-cost, portable, smartphone-based autorefractor (Netra, EyeNetra Inc., Somerville, MA) in adults.

METHODS A cross-sectional study was conducted to compare the portable refractor with subjective (manifest and cycloplegic) refraction for sequential adult participants with best-corrected visual acuity of 20/40 or greater. For each method of refraction, the spherical equivalent was calculated. Differences between methods were tested with linear mixed regression models. A validated usability questionnaire was administered regarding ease of use (100-point scale, higher scores better) for the portable autorefractor.

RESULTS Eighty-seven subjects (152 eyes) were studied (age range, 20 to 90 years; mean ± standard deviation, 51.9 ± 18.3 years). Mean spherical equivalent by the portable device was −2.76 D (range, −14.75 to 3.63 D) compared with −2.49 D (range, −15.25 to 4.25 D) by manifest refraction. The mean relative difference in spherical equivalent between methods was −0.27 D (P = .001, significantly different than 0 D). The mean absolute difference between methods was 0.69 D (P < .001, significantly different than 0.5-D absolute difference). Similar results were found when comparing spherical equivalent between Netra and cycloplegic refraction methods. Subjects reported average ease of use for the Netra of 75.4 ± 19.8.

CONCLUSIONS The portable autorefractor had small but clinically significant differences from subjective refraction. The device's scores on the usability scale indicate good overall patient acceptance. The device may be valuable for use where there is limited access to a trained refractionist.

1Department of Ophthalmology and Visual Sciences, W. K. Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan

2Institute for Healthcare Policy and Innovation, University of Michigan, Ann Arbor, Michigan *

Supplemental Digital Content: Appendix Table A1, available at Comparison of monocular best corrected visual acuity obtained between EyeNetra refraction and manifest refraction (n = 152 eyes) and EyeNetra refraction and cycloplegic refraction (n = 74 eyes).

Appendix Figure A1, available at The external appearance of the EyeNetra device with attached dedicated smartphone with processing, WiFi, and Bluetooth capabilities (Samsung Galaxy S4).

Submitted: November 20, 2017

Accepted: July 22, 2018

Funding/Support: National Eye Institute (United States) (K23EY023596; to MAW); and Warby Parker (to MAW).

Conflict of Interest Disclosure: MAW is a consultant for Simple Contacts.

Author Contributions: Conceptualization: NV, MAW; Data Curation: VSEJ, NV, HA, MAW; Formal Analysis: LMN, MAW; Investigation: SH, HA, MAW; Methodology: MAW; Supervision: MAW; Validation: SH; Writing – Original Draft: VSEJ; Writing – Review & Editing: NV, LMN, SH, MAW.

Supplemental Digital Content: Direct URL links are provided within the text.

© 2018 American Academy of Optometry