Smartphone App Shows Promise for Visual Acuity Testing

Jennifer Garcia

June 03, 2015

A smartphone-based test for visual acuity is as accurate and repeatable as currently available standard visual acuity tests, according to a new study published online May 28 in JAMA Ophthalmology.

The researchers, led by Andrew Bastawrous, MRCOphth, from the London School of Hygiene & Tropical Medicine in the United Kingdom, used a smartphone-based, logMAR-style vision test (Peek Acuity) to measure visual acuity among adults in rural Africa. They compared results, measurement time, and test-retest reliability with the most commonly used acuity test, the Snellen chart.

The study enrolled a total of 233 participants aged 55 years or older between December 11, 2013, and March 4, 2014. Participants were part of the ongoing Nakuru Eye Disease Cohort in central Kenya. Vision tests were administered on 2 consecutive days — once in the participant's home and once in the clinic — and were performed by people both with and without healthcare training.

In comparisons of clinic-based Snellen and clinic-based Peek Acuity measures with the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart, Snellen tests showed a high degree of correlation with the ETDRS chart. The correlation was even higher with Peek Acuity (95% confidence interval, 0.05 - 0.10; P = .08). The test–retest reliability of Peek Acuity, performed by the same tester at home and in the clinic, was also found to have a high correlation.

"Peek Acuity used at home by a community health care worker was 85% sensitive and 98% specific at detecting eyes with severe visual impairment (deemed locally as the surgical cutoff point for operable cataract; Snellen equivalent of ≤6/60) when compared with the ETDRS testing in controlled conditions," the authors explain.

The smartphone application follows the standard ETDRS chart design, with a letter E displayed in one of four orientations (90°, 180°, 270°, and 0°). The tester can then use the touch screen to swipe in the direction indicated by the patient, based on their perception of what direction the arms of the E are pointing. The application also provides alternatives to finger counting, hand movements, and light perception, which are part of standard visual acuity testing.

"Overall, Peek Acuity performed well and the testing time was no slower or less repeatable than with the Snellen test, while being comparable in accuracy to the ETDRS chart," the researchers write.

The authors acknowledge limitations of the study such as the limited generalizability of the findings as a result of testing within this specific population of older adults in rural Africa. They note that availability of smartphones in low-income settings is also a concern.

"[W]ithin some limits, this cell phone and stored app seems to work well in documenting visual acuity when compared to current well-established and well-documented methodology," Ivan Schwab, MD, clinical spokesperson for the American Academy of Ophthalmology and a professor of ophthalmology at the University of California, Davis, told Medscape Medical News.

"[W]e have tried and true mechanisms that have already been better tested and agreed upon," Dr Schwab said when asked if an application like this would be very useful in developed countries such as the United States.

"This app may have limitations in the developing world as well, related to cost, reliability, energy requirements, and fragility, among others," Dr Schwab noted.

Funding for this study was provided by the Medical Research Council, the Department for International Development, the International Glaucoma Association, the British Council for the Prevention of Blindness, and the Queen Elizabeth Diamond Jubilee Trust. Dr Bastawrous and two coauthors have a patent pending on the Peek Vision retina hardware. Dr Schwab has disclosed no relevant financial relationships.

JAMA Ophthalmol. Published online May 28, 2015. Full text

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