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To the Editor:
—With regard to the letter of Lieut. Col. Edwin N. Beery in the June issue (Arch. Ophth.29: 1025, 1943), it is true that were the naval examiner to go beyond the notation 20/400 (1/20) he would necessarily have to modify his designation of visual acuity. That is, he would have to revert—in the instance cited—to the use of unity as expressed in 80/80 rather than 20/20 ; in other words, 5/400 reduced to 1/80 has a corresponding unity of 80/80. As previously pointed out, unity here has the same subtending angle of 5 minutes of arc as that indicated by the standard norm of 20/20.Granting any such modification, however, it becomes apparent that this scale of visual symbols in effect can no longer obtain. Hence it may be seen that, although convenient for the special purpose it serves, this method is definitely restrictive in scope and
Gabriels JAC. SNELLEN SYMBOLS AND THE NAVAL EXAMINER. Arch Ophthalmol. 1943;30(3):377. doi:10.1001/archopht.1943.00880210101012
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