Tumbling "E" suitable for illiterate and preliterate patients Useful for multiple languages Tumbling or Illiterate "E" charts are very reliable alternative visual acuity tests. Although Landolt "C" tests are considered the standard in alternative vision tests, many studies have proven that Tumbling "E" tests are nearly equal. In fact, because of their shape, Tumbling "E"s have grating properties and have been proven to be almost better then Landolt "C"s in visual acuity establishment.