Snellen Visual Acuity Unmatched By Smartphone Apps

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Nice girl with new eyeglasses. Holding her smartphone and smiling to the camera. Fashionable children’s eyeglasses. Video conference with her mother to confirm the choice.
Researchers compared the accuracy of 3 smartphone applications with the Snellen chart to assess their utility in teleophthalmology.

This article is part of Ophthalmology Advisor’s conference coverage from the 2021 meeting of the American Academy of Ophthalmology, held in New Orleans from November 12 to 15, 2021. The team at Ophthalmology Advisor will be reporting on a variety of the research presented by the ophthalmology experts at the AAO. Check back for more from the AAO 2021 Meeting.


Visual acuity monitoring is essential in monitoring disease progression and overall visual health. Patients who could benefit from regular visual acuity checks could find an app-based option that can not only monitor their acuity, but share that data with their ophthalmologists. However, an investigation presented at the American Academy of Ophthalmology 2021 meeting in New Orleans shows that some of the available apps may not deliver the consistent results necessary to closely monitor visual health. 

Researchers reviewed the accuracy of 3 different smartphone apps (Eye HandBook, Smart Optometry and EyeXam) and compared their findings with that of a traditional Snellen chart to assess their utility as a tool for teleophthalmology.

“None demonstrated agreement with the Snellen chart within 1 line,” the investigators reported. 

The research took into account 161 participants recruited from the Emory Eye Center. Each patient’s eyes were assessed using a Snellen chart and 1 of the apps. In total, 100 eyes were tested with Eye HandBook, 101 with Smart Optometry, and 100 with EyeXam. 

The study found a mean difference in logMAR acuity between Eye HandBook and Snellen chart of 0.01 logMAR (95% limit of agreement, -0.29, 0.29 logMAR). The difference between the Smart Optometry app and Snellen chart was -0.02 logMAR (95% limit of agreement -0.48, 0.44 logMAR). The EyeXam differed from the Snellen chart by 0.07 logMAR (95% limit of agreement -0.26, 0.40 logMAR), according to the findings.

Smartphone apps “should be used with caution in teleophthalmology, as none demonstrated agreement with the Snellen chart within 1 line,” the report said. “This study additionally highlights key features that could be improved upon in the development of future visual acuity applications.”

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Schaffer L, Kim HJ. Evaluation of three smartphone apps for va testing. Poster presented at: The American Academy of Ophthalmology 2021 Annual Meeting; November 12-15; New Orleans. Abstract PO199.