Screening for color blindness using optokinetic nystagmus.

Red/green luminosity ratios were determined by a new method. A special colored grating of red and green bars appeared to move to the left (or right) when the red bars were darker (or lighter) than the green bars. Optokinetic nystagmic eye movements (OKN) elicited by this stimulus could be measured photoelectrically, or by directly watching the subject's eyes. When the red/green ratio passed through equiluminance, the direction of apparent movement (AM) and of OKN reversed in direction. Protans needed more red than normals to reach equiluminance, and deutans needed more green. This OKN method might be applied to nonverbal subjects such as infants and animals.