Background: A visual acuity (VA) testing application for the iPad® (Apple, Cupertino, CA) tablet computer using the mirroring technique was developed that randomly presented letters categorized by cognoscibility. The aim of this study was to assess whether measurements of distance VA using this application were in agreement with existing standard clinical tests of VA in adults with normal vision.
Materials and methods: Forty-three normally sighted subjects were tested using the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart. The log minutes of arc (logMAR) VA results were compared with those from the iPad-based application, which contains a Snellen chart, a Tumbling E chart, a Landolt C chart, and a VA chart consisting of Arabic figures. After a 10-min break, subjects were retested with each test in the same order. Agreement was assessed by determining the 95% limits of agreement ± 1.96 standard deviation of the differences between tests.
Results: The logMAR VA showed no significant difference between the ETDRS chart and the iPad Snellen chart (p = 0.66) and iPad Arabic figure chart (p = 0.29). The logMAR VA of the ETDRS chart was significantly better than that of the iPad Tumbling E chart (p < 0.01) or iPad Landolt C chart (p < 0.01). The subjects showed chart letter memory of the ETDRS chart (p < 0.05), Tumbling E chart (p = 0.03), and Landolt C chart (p = 0.001) but not of the iPad Snellen chart (p = 0.62) and iPad Arabic figure chart (p = 0.12).
Conclusions: The iPad-based application of VA charts showed similar repeatability and may be a rapid and convenient alternative to some existing measures. The mirroring technique provides portability and accessibility for VA charts.
Keywords: Early Treatment of Diabetic Retinopathy Study chart; application; iPad; visual acuity; visual acuity chart; visual assessment.