Eye app for iPad validated for measuring visual acuity

A study comparing an iPad app using a portable Snellen chart found it is comparable to the traditional chart for measuring visual acuity.

The EyeSnellen app for iPad and iPhone has been designed by Perth ophthalmologist Steve Colley, who works in private practice at the Western Eye clinic as well as at Royal Perth and Fremantle hospitals.

Released in 2012 with an update in December last year, the EyeSnellen uses an iPad to display the Snellen chart and an iPhone or iPod as a remote device via Bluetooth.

In a paper published in the open access Journal of Mobile Technology in Medicine (JMTM) last week, Fremantle Hospital researchers found that of 67 people with an average age of 57 tested, the Snellen chart function on the EyeSnellen app was equivalent to the traditional Snellen chart at measuring visual acuity at a test distance of six metres.

As the authors write, measurement of visual acuity provides a screening tool for the diagnosis of underlying disease and can be used as a predictor of the functional consequences of visual loss.

The original Snellen chart, developed in 1862 by Dr Herman Snellen, is still the gold standard using a light box. Although there are many apps available, few have been standardised and validated and the authors say there has not been a study validating the use of a Snellen chart on a tablet device.

The authors – Fremantle Hospital RMOs Pavindran Gounder and Eliza Cole, medical student David Hille and Dr Colley – say that the portability of tablet devices makes them ideal for remote and rural healthcare and for mobile screening units, so they wanted to test the hypothesis that the EyeSnellen app could be confidently used in these settings.

Participants for the study were recruited from the Fremantle Hospital Eye Clinic over a period of two weeks, with visual acuity measurements assessed and recorded by two resident medical officers.

Of the 67 participants, 122 eyes were tested. Diagnoses included corneal pathology, glaucoma, cataracts, dry eye syndrome and seven were post-operative.

Their analysis showed agreement between visual acuity measured by Snellen chart on EyeSnellen and visual acuity measured by the Snellen light box chart.

“This result demonstrates that EyeSnellen can be used as an alternative to the traditional Snellen light box chart when vision is tested at 6 metres,” they write.

They found some advantages of the EyeSnellen app, including the fact that the remote function allowed randomisation of optotypes (test symbols), which removed the chance of patients recalling optotypes from memory.

“Another advantage of the app allowed assessors to observe the letters and visual acuity interval on the remote, which made the recording of visual acuity easier,” they write.

They conclude that the Snellen chart function on the EyeSnellen app can be reliably used to measure visual acuity in clinical settings.

“Furthermore, the application may be more advantageous than traditional light box charts due to its portability and the ability to randomise optotypes.”

Dr Colley has also designed two other apps, one a vision test that can be done at home, and the other a quick lens transposer for spectacle prescriptions.

Posted in Australian eHealth

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