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Brief Report
January 14, 2021

Visual Acuity Testing for Telehealth Using Mobile Applications

Author Affiliations
  • 1Department of Ophthalmology and Visual Sciences, Yale School of Medicine, New Haven, Connecticut
JAMA Ophthalmol. 2021;139(3):344-347. doi:10.1001/jamaophthalmol.2020.6177
Key Points

Question  Are there any available visual acuity Apple apps suitable for telemedicine use?

Findings  In this study of diagnostic devices, none of the tested visual acuity apps were ideal for telemedicine.

Meaning  While clinicians are limited to apps on iPhone or iPad, these results suggest new and/or improved visual acuity apps are needed for optimal use in telemedicine.


Importance  The coronavirus disease 2019 pandemic illustrates the increasingly important role of telemedicine as a method of clinician-patient interaction. However, electronic applications (apps) for the testing of ophthalmology vital signs, such as visual acuity, can be published and used without any verification of accuracy, validity, or reliability.

Objective  To reassess the accuracy of visual acuity–testing apps and assess their viability for telehealth.

Design, Setting, and Participants  The US Apple App Store was queried for apps for visual acuity testing. Anticipated optotype size for various visual acuity lines were calculated and compared against the actual measured optotype size on 4 different Apple hardware devices. No human participants were part of this study.

Main Outcomes and Measures  Mean (SD) errors were calculated per device and across multiple devices.

Results  On iPhones, 10 apps met inclusion criteria, with mean errors ranging from 0.2% to 109.9%. On the iPads, 9 apps met inclusion criteria, with mean errors ranging from 0.2% to 398.1%. Six apps met criteria and worked on both iPhone and iPad, with mean errors from 0.2% to 249.5%. Of the 6 apps that worked across devices, the top 3 most accurate apps were Visual Acuity Charts (mean [SD] error, 0.2% [0.0%]), Kay iSight Test Professional (mean [SD] error, 3.5% [0.7%]), and Smart Optometry (mean [SD] error, 15.9% [4.3%]). None of the apps tested were ideal for telemedicine, because some apps displayed accurate optotype size, while others displayed the same letters on separate devices; no apps exhibited both characteristics.

Conclusions and Relevance  Both Visual Acuity Charts and Kay iSight Test Professional had low mean (SD) errors and functionality across all tested devices, but no apps were suitable for telemedicine. This suggests that new and/or improved visual acuity–testing apps are necessary for optimal telemedicine use.

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1 Comment for this article
Testing distances
Hazel Kay | Kay Pictures Ltd
I wondered why you chose to test at 40cm with the iSight Pro app when other test distances up to 300 cm are available on the iphone and up to 600cm on the ipad, including your preferred 400cm distance?

Unless the test distance was scrupulously monitored, the small inaccuracy you found could be due to the test distance, rather than the app itself.

I realise that you stated that the iSight app was most accurate, but your table showed otherwise.

We have plans for a remote option for this app. Please get in touch if you
are interested.
CONFLICT OF INTEREST: I develped the iSight Pro app mentioned