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J. A. C. Gabriels, M.D.
Albany, N. Y.

Arch Ophthal. 1943;30(1):138.

	Since this article does not have an abstract, we have provided the first 150 words of the full text PDF and any section headings.

To the Editor:

—Various attempts have been made to find a suitable formula for conversion of conventional Snellen symbols into less conventional equivalents. An acceptable method and its accompanying rationale are here briefly outlined.

With, for example, Sn 20/25 (binocular requirement for Naval inductees), the proper procedure is illustrated in the following equation :

or

Therefore 16/20 is the equivalent of 20/25. Conversely, with Sn 16/20:

or

Therefore 20/25 is the equivalent of 16/20.

It is evident from the foregoing that, as defined, these Snellen notations represent a relation or ratio of two numerical values of the same kind and denote one or more aliquot parts of a unit, while expressing at the same time a definite proportion; in short, each by its very nature connotes a true fraction. I have on several occasions demonstrated the validity of such a premise. Hence this conversion formula has a sound basis in fact, . . . [Full Text PDF of this Article]

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