Eye chart chart or Jaeger chart can be used. While the Snellen chart remains the default, some authors have argued that the logMAR chart is superior. The logMAR chart presents the same number of symbols on each line, uses a typeface with letters that are equally legible at various sizes, and by varying the symbol size logarithmically, it is easier to use at nonstandard distances. As a consequence of these improvements, the logMAR chart has been proposed as a more reliable tool for measuring visual acuity. However, the logMAR chart has not yet been widely adopted. It can be difficult to measure
Three letter rule Three letter rule In English spelling, the three letter rule (or short word rule) is the observation that one- and two-letter words tend to be function words such as "I", "at", "he", "if", "of", "or", etc. As a consequence of the rule, "content words" tend to have at least three letters. In particular, content words containing fewer than three phonemes may be augmented with letters which are phonetically redundant, such as "ebb, "add, "egg, "inn, "bee, "awe, "buy", "owe", etc. Many content words would be homographs of common function words if not for the latter's "redundant" letters: e.g. "be/bee", "in/inn",