The Eye Phone Study: reliability and accuracy of assessing Snellen visual acuity using smartphone technology.
OBJECTIVE
Smartphone-based Snellen visual acuity charts has become popularized; however, their accuracy has not been established. This study aimed to evaluate the equivalence of a smartphone-based visual acuity chart with a standard 6-m Snellen visual acuity (6SVA) chart.


METHODS
First, a review of available Snellen chart applications on iPhone was performed to determine the most accurate application based on optotype size. Subsequently, a prospective comparative study was performed by measuring conventional 6SVA and then iPhone visual acuity using the 'Snellen' application on an Apple iPhone 4.


RESULTS
Eleven applications were identified, with accuracy of optotype size ranging from 4.4-39.9%. Eighty-eight patients from general medical and surgical wards in a tertiary hospital took part in the second part of the study. The mean difference in logMAR visual acuity between the two charts was 0.02 logMAR (95% limit of agreement -0.332, 0.372 logMAR). The largest mean difference in logMAR acuity was noted in the subgroup of patients with 6SVA worse than 6/18 (n=5), who had a mean difference of two Snellen visual acuity lines between the charts (0.276 logMAR).


CONCLUSIONS
We did not identify a Snellen visual acuity app at the time of study, which could predict a patients standard Snellen visual acuity within one line. There was considerable variability in the optotype accuracy of apps. Further validation is required for assessment of acuity in patients with severe vision impairment.
1] Journal of Mobile Technology in Medicine [2] Department of Ophthalmology, Fremantle Hospital, Western Australia, Australia.
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C
Perera
1] Journal of Mobile Technology in Medicine [2] Department of Ophthalmology, Centre for Eye Research Australia, University of Melbourne, Victoria, Australia.
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R
Chakrabarti
1] Department of Ophthalmology, Centre for Eye Research Australia, University of Melbourne, Victoria, Australia [2] Department of Psychological Sciences and Statistics, Faculty of Health, Arts and Design, Swinburne University of Technology, Victoria, Australia.
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FM
Islam
Department of Ophthalmology, Centre for Eye Research Australia, University of Melbourne, Victoria, Australia.
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J
Crowston
D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D063731:Mobile Applications; D011446:Prospective Studies; D015203:Reproducibility of Results; D000068997:Smartphone / Q000592:standards*; D014787:Vision Tests / Q000295:instrumentation / Q000592:standards*; D014792:Visual Acuity / Q000502:physiology*