Abstract
Purpose:
A visual acuity (VA) testing app for the iPad tablet computer using mirroring technique was developed which 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 standard clinical tests of VA in adults with normal vision.<br />
Methods:
Forty-three normally sighted subjects were tested using Early Treatment of Diabetic Retinopathy Study (ETDRS) chart. The 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 consisted with Arabic figures. After a 10-min break, subjects were retested with each test in the same order. Repeatability was assessed by testing the subjects 1-day later with each visual chart. Repeatability and agreement were assessed by determining the 95% limits of agreement (LoA) ± 1.96 SD of the differences between tests.<br />
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 iPad Tumbling E chart (P<0.01) and iPad Landolt C chart (P<0.01). The subjects showed no chart letter memory of the ETDRS chart (P=0.05), iPad Snellen chart (P=0.62), and iPad Arabic figure chart (P=0.12). The logMAR VA of Tumbling E chart (P=0.03) and Landolt C chart (P=0.001) was significantly better at 10 min.<br />
Conclusions:
The iPad-based application of VA charts showed similar repeatability and may be a rapid and convenient alternative to some existing measures. Mirroring technique allows the visual chart to be presented avoiding the glare due to the glossy screen of the iPad tablet.<br />