Contribution of electroretinography to diagnosis of color vision deficiencies

The role that electroretinography (ERG) has played in the past and might play in the future in the study of color vision deficiencies is discussed in this paper. First, an example is given of how Copenhaver and Gunkel concluded in 1958 the absence of the green cone system in deuteranopia before Rushton, with the more direct method of densitometry, reached the same conclusion. Padmos and van Norren showed in 1971 that chromatic adaptation did not change a dichromat's spectral sensitivity curve, which fits the model of a loss system. A comparison between dichromats' spectral sensitivity curves based on the rapid off-response and recent data on single monkey receptors showed a slight but systematic discrepancy, indicative of a rod contribution in the off-response method. Carriers of color vision deficiencies might be more readily detected with an ERG than with a psychophysical method. The early receptor potential (ERP) seems a less suitable means to study color vision deficiencies. The blue cones form an interesting subject of study since they seem to be the most vulnerable cone type. With an ERG method a localization of acquired tritan deficiencies is possible. A recent finding is that blue cones are substantially more sensitive to light damage than either rods, or red or green cones.