Best Corrected Visual Acuity (BCVA) is tested using the familiar ETDRS chart. The chart also appears on the iPad, where the tester records the responses with a single tap. The chart is implemented following the recommendations described in Ferris et al. (1982)1
BCVA can also be measured using optotypes with and without crowding bars. The test is implemented using a finer scale of letter sizes, allowing detection of more subtle changes in visual acuity.
This test is more appropriate for pre-readers, illiterates and subjects unfamiliar with the Latin alphabet. The size of the individual optotypes can exceed 1.0 logMAR, which makes it convenient when assessing subjects with low vision.