Development and Validation of a Smartphone-Based Visual Acuity Test (Peek Acuity) for Clinical Practice and Community-Based Fieldwork – JAMA Ophthalmol. Published online May 28, 2015. doi:10.1001/jamaophthalmol.2015

“Visual acuity (VA) is the most frequently performed measure of visual function in clinical practice. Visual acuity measurements are used to establish the need for clinical investigation and quantify changes in central vision over time. Four percent of those who attend general practice in the United Kingdom do so with an eye problem and a formal measure of VA should be part of each of these consultations. Globally, 285 million people have visual impairment, with 80% having diseases with known curative or preventive treatment. However, most live in low-income countries with minimal access to detection and subsequent treatment. The Snellen chart 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. Different letters or optotypes (standardized symbols for testing vision) have varying legibility at the same size and secondary effects, such as crowding, are known to affect the ability of the patient to determine optotypes correctly and therefore could lead to measurement bias. The limitations of the Snellen chart have largely been overcome with the development of logMAR acuity charts, which are now frequently used in clinical research, such as the Early Treatment of Diabetic Retinopathy Study (ETDRS) charts. Despite this improvement, the Snellen chart remains the dominant method for acuity testing in clinical practice. This may be owing to several factors including familiarity, a well-recognized scoring system, smaller chart size, and the speed of performing the test relative to the ETDRS chart test. Mobile telephone technology has evolved rapidly in recent years. In 2013, an estimated 280 million (20%) of the 1.4 billion mobile telephones sold were smartphones and this proportion is expected to increase, particularly in low-income settings, where fixed-line technology has been leapfrogged straight to mobile technology, providing the potential to access health care without the previously required infrastructure. The medical community is embracing mobile technologies with its potential in health care information delivery, real-time patient monitoring, research data collection, and mobile telemedicine for the provision of expertise to remote locations. We hypothesized that a logMAR-style smartphone-based vision test (Peek Acuity), with a fast-testing algorithm, would allow measurements to be made in a clinically acceptable time, with greater precision and reliability than is possible with Snellen charts. Visual acuity results can be displayed in familiar Snellen chart notation (imperial or metric) or logMAR. The Peek Acuity test was developed and compared, in terms of test-retest variability (TRV) and measurement time, with the Snellen chart and the ETDRS-based tumbling E logMAR chart (reference standard) in controlled and uncontrolled (real-world) settings in rural Kenya.”