[Discussion on logarithmic visual acuity chart and five grade notation].
To explore the scientific aspect of logarithmic visual acuity chart and five grade notation, a visual test-type ten times large as the test-type of 4.0 grade was put 0.5 m before the eye, if the eye saw it, then the visual acuity was 2.0 grade (visual angle 1000' = 16.67 degrees). If moving this test-type to 0.05 m before the eye, 1.0 grade (visual angle 10 000' = 166.7 degrees) was obtained. They are more scientific than original records: hand movement for 2.0 grade and light perception for 1.0 grade. These test-type theoretically satisfy the demand of 5 grade notation. Logarithmic visual acuity chart and 5 grade notation is more superior subject created in China.
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