These iPad-based logMAR visual acuity charts are based on the Bailey-Lovie Visual Acuity Chart. The test uses the same 10-letter set as the Bailey-Lovie chart. The ten letters appear in a random order and have been shown to have similar visibility.
Unlike printed tests, these charts require no external lighting and runs on the ubiquitous iPad without need for special software or calibration. The test utilizes the high quality iPad screen to produce letters small enough to measure visual acuity at test distances as short as 6 feet or 2 meters.
The main charts have ten lines of letters. The supplemental charts have two larger letters but the charts are not ideal for the assessment of severely visually impaired patients. At a test distance of 5 feet (1.5 meters) the largest letters will correspond to 20/200 (6/60).
Low contrast versions of the chart are also provided. The letters is 10% Weber contrast. In other words the luminance of letters is 90% of the background.
The logMAR design of the chart may be leveraged to take more precise measurements. Credit may given for each individual letter read correctly (0.02 log units). On the last page, there is a table giving the logMAR values for each line for a number of test distances. A spreadsheet that will calculate logMAR based on the patient’s responses for any test distance can be requested at ridgevue.com
Other Ridgevue Vision tests are available from the iTunes store.
For more information visit ridgevue.com
