Eye Testing App is as Accurate as Traditional Charts

A smartphone app to test eyesight works as well as charts for visual acuity (VA), according to a new study.

Developed by researchers at the London School of Hygiene & Tropical Medicine (LSHTM; United Kingdom), the University of Strathclyde (United Kingdom), and other institutions, the Portable Eye Examination Kit (Peek) is a unique smartphone-based system for comprehensive eye testing anywhere in the world. It consists of a hardware element, the Peek Retina, and a series of apps. One of the apps, called Peek Acuity, determines how clearly an individual sees by displaying the letter E in 1 of 4 orientations.


The patient points in the direction they perceive the arms of the E to be pointing, and the tester uses the smartphone touch screen to swipe accordingly, thus translating the gestures from the patient to the phone. The results of the Peek VA test were compared--in terms of test-retest variability and measurement time—with the traditional Snellen acuity and Early Treatment of Diabetic Retinopathy Study (ETDRS) logMAR charts in participants’ homes and temporary clinic settings in rural Kenya in 2013 and 2014.

The results of the comparison among 233 people showed that the mean differences between the smartphone-based test and the ETDRS chart, and the smartphone-based test and Snellen acuity data were 0.07 and 0.08, respectively, indicating that the smartphone-based test results agreed well with those of the ETDRS and Snellen charts. Average testing time was also measured and found that the commonly used Snellen test took 82 seconds compared with 77 seconds for Peek Acuity. The study was published on May 28, 2015, in JAMA Ophthalmology.

“With most of the world’s blind people living in low-income countries, it is vital we develop new tools to increase early detection and appropriate referral for treatment. Mobile phone use is now so widespread that it seemed to be an ideal platform,” said lead author Andrew Bastawrous, MD, of the LSHTM. “Our ultimate hope is that the accuracy and easy to use features of Peek will lead to more people receiving timely and appropriate treatment and be given the chance to see clearly again.”

The Snellen chart, which uses decreasing letter size, is the most common method for the measurement of VA in ophthalmic and general practice; however, it is limited by the nongeometric progression in letter sizing from line to line and the inconsistent number of letters per line. These limitations were largely overcome with the development of ETDRS logMAR acuity charts, which are now frequently used in clinical research. Despite this improvement, the Snellen chart remains the dominant method for acuity testing in clinical practice.

Related Links:
London School of Hygiene & Tropical Medicine
University of Strathclyde