Comparing the Netra smartphone refractor to subjective refraction

Abstract

Background

Among technologies targeting mobile eye care, EyeNetra is a smartphone‐based subjective refraction system. This study compared the results from this system with those of professional subjective refraction. Participant visual comfort and preference of results were also measured.

Methods

Thirty‐six optometry‐naïve participants (n = 36 eyes, aged 18–35 years), were randomly subjected to three refraction methods: professional subjective refraction, unassisted Netra (participants alone) and refined Netra (sphere results refined by a practitioner). Using a randomised, double‐blind design, refraction results were mounted in a trial frame and distance logMAR visual acuities were measured. Subjective appreciation and visual comfort were assessed by questionnaire. Overall preference was ranked.

Results

Unassisted Netra yielded a median myopic overcorrection of 0.60 D (interquartile range [IQR] 0.25 to 0.94) compared to professional subjective refraction. Median equivalent sphere with unassisted Netra (−1.40 D, IQR −3.10 to −0.90) was significantly more myopic than refined Netra (−0.70 D, IQR −1.60 to −0.30) and then subjective refraction (−0.80 D, IQR −1.60 to −0.30) (all p‐values < 0.01). Median visual acuity with professional subjective refraction (−0.16, IQR −0.22 to −0.09) was superior than unassisted Netra (−0.08, IQR −0.20 to 0.03) (p < 0.01). Subjective refraction was ranked first in preference of trial framed results by 72 per cent of participants; median preference rank favoured professional subjective refraction to both Netra results (all p < 0.01). For all questionnaire items, visual comfort was higher with subjective refraction than with unassisted Netra (all p < 0.04).

Conclusion

The Netra device – especially when used without professional assistance and compared to subjective refraction – induces significant myopic overcorrection and lower levels of visual acuity, subjective preference and visual comfort.

Key words:

• diagnostic techniques
• instrumentation
• ocular
• ophthalmological instrumentation
• refractive errors
• telemedicine
• vision tests

ACKNOWLEDGEMENTS

The authors would like to thank Exeko, a non‐profit community organisation fighting social exclusion and promoting access to eye care for marginalised populations, for their help in developing the study concept and for supplying the EyeNetra system.

Supporting information

Additional supporting information may be found in the online version of this article at the publisher’s website:

Appendix S1. Subjective appreciation and comfort questionnaire.