Converts Snellen visual acuity fractions (20/20, 20/40, 20/200, etc.) to decimal notation and LogMAR values. 20/20 = 1.0 decimal = 0.0 LogMAR; 20/40 = 0.5 = 0.3 LogMAR; 20/200 = 0.1 = 1.0 LogMAR. Used to standardize acuity reporting across international systems.
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