Eye charts with letters versus rings do not measure visual acuity the same way
Photo by Vanessa Bumbeers on Unsplash
What is it about?
Most people are familiar with eye charts that display letters. There are other charts that have rings with a gap at different orientations, which can be used with persons that cannot read or speak; however, visual acuities that are measured with letters are often better than those measured with rings because people are better at guessing a letter from the context of its lines and circles.
Why is it important?
Studies that involve visual acuity across the globe are often compared with one another, but this only makes sense of the different measurement techniques are actually comparable. Many Asian and African countries use rings or tumbling E letters to test vision because participants only need to indicate a direction, and not need to be able to read a specific alphabet.
The following have contributed to this page: Dr Walter Wittich