In the report of the Committee on Definition of Blindness,1 the value of vision is expressed in terms of the fractional or decimal equivalent of the Snellen symbol, e. g., 20/200 or 6/60 or 0.1. This is at variance with the visual ratings as proposed by the Committee on Compensation Tables for Eye Injuries—a committee of the Section of Ophthalmology of the American Medical Association. Whether the Snellen formula represents a true fraction has long been a source of controversy. I have repeated elsewhere2 proof of the inherent fractional nature of the Snellen notation. Such recognition, as pointed out, does not warrant its acceptance for measuring the value of vision. Adoption of values based on the unit of surface rather than on the subtending visual angle or linear unit is again suggested as offering the only solution to this problem.
Briefly, what one determines with the Snellen test
Gabriels JAC. THE CALCULATION OF LOSS OF VISION. Arch Ophthalmol. 1935;13(4):635–636. doi:10.1001/archopht.1935.00840040125010
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