Objective examination of genetic carrier of congenital red-green color blindness by Electroretinography

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The rapid off-response in the ERG was previously reported in the human to be composed mainly of the decay of the late receptor potential of cones at particular stimulus parameters. The present study describes the spectral sensitivity of the rapid off-response in proto-carrier and deutero-carrier subjects, with an ultimate purpose of an objective detection of a genetic carrier of congenital red-green color blindness at receptor level.The mean of the sensitivity of the rapid off-response was lower at 540 nm and longer wavelengths, and higher at 480 nm and 500 nm in protocarriers, as compared with normal control. The mean sensitivity of the rapid off-response was slightly lower at 560 nm amd shorter wavelengths, and higher at 600 nm and 620 nm in dentero-carriers than in normal subjects.The changes of the sensitivity in the carriers mentioned above was not so prominent as in protans and dentans. Thus the mean spectral sensitivity curve in the proto- or dentero-carriers lay between the curves in normal subjects and those in respective color blindness (pcotans, deutans).The ratio of the sensitivity at 480 nm to the sensitivity at 620 nm in protocarriers tended to be smaller than the ratio in protans, and larger than the ratio in normal subjects. The ratio in most of dentero-carriers was smaller than normal.The findings of the present study demonstrate that some of proto-carriers and deutero carriers are abnormal at the level of cone receptor level.