Visual acuity measurements - hicsoap.com

Guest editorialVisual acuity measurementshas been done incorrectly in most basicModern Visual acuity charts are designed so the lettersizes on each line follow a geometric progressionproblem relates to the difference between the arithmeticand geometric mean for a set of numbers. For the correct(ie, change in a uniform step on a logarithmic scale).1 3 The accepted step size has been chosen to be logaverage Visual acuity , the geometric mean must be used,unit, which is equivalent to letter sizes changing by awhich gives significantly different values than the arith-factor of between lines. This standard gave risemetic the logMAR (logarithm of the minimum angle ofThe simplest method for computing the proper aver-resolution) notation as shown in Table 1, column 3. Theage Visual acuity from any notation is to convert the valueboldvalues correspond to the accepted logMAR the logMAR equivalent and then take the average of theValues that are not in logMAR steps such as 20/30,logMAR values.

30 1000.00 0.03 3.00 0 20000† 6000.0 0.001 0 14000.0 35000.0 — — 400.0 Bold values are standard logMAR progression. LogMAR logarithm of the minimum angle of resolution *20/2000 is equivalent to counting fingers @ 2 feet †20/20000 is equivalent to hand motion @ 2 feet

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