A recently discovered component of the human electroretinogram (the electrical response wave resulting from stimulation by light) is recorded with an electrode mounted in a contact lens. Although previous investigators have thought it to be a photopic response, this component of the ERG is found to have a spectral sensitivity function that is maximal at approximately 630 mμ and is not similar to either a photopic or a scotopic luminosity function. This component is absent in the eyes of protanopes (red color blind) but present in eyes characterized by other forms of color deficiency. It increases rapidly with dark adaptation and is greatest after approximately one minute in darkness. It is accompanied by several new and previously unreported waves which also make their appearance during the early stages of dark adaptation. This research provides direct physiological evidence for a peripheral locus of color blindness and for a specific red color mechanism.
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