Abstract: The recovery time in discriminating a 6' gap of Landolt Ring after abrief intense light was measured for dark-adapted eye of 11 male subjects withnormal vision. Bloch's law holds for flash duration from 0.1 to 5 ms andintegrated luminance from 0.06 to 1.96 stilb sec. Consequently the occlusiontime of the protecting glass can be determined by satisfying the relationshipbetween recovery time and integrated luminance.

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