Abnormal spectral sensitivity of electroretinographic off-response in protanopia and protanomalia
Nakazato, H.; Kawasaki, K.; Yonemura, D.; Kawaguchi, I.
Nippon Ganka Gakkai Zasshi 85(10): 1513-1520
1981
ISSN/ISBN: 0029-0203 PMID: 6977987 Document Number: 176813
Congenital dyschromatopsia was studied electroretinographically. Most similar studies dealt with the b-wave or flicker response, which is contributed by postsynaptic components. They provided no conclusive information on abnormality of photoreceptors in dyschromatopsia. The rapid off-response in the ERG in the human and monkey was previously reported to be composed mainly of the decay of the late receptor potential from cones at particular stimulus parameters. Presently, the spectral sensitivity of the rapid off-response in normal and protanopic subjects were studied to objectively determine congenital dyschromatopsia at the receptor level. The ERG was evoked by repetitive rectangular monochromatic stimuli having equal quanta. Stimulus light of 125 ms duration was repeated at 4 Hz. Averaged waveforms of 40 responses were analyzed. The amplifier time constant was 2 s. The pupil was fully dilated. The spectral sensitivity curve of the rapid off-response in normal subjects peaked at 550 nm, and approximated in shape the human photopic visibility curve. The spectral sensitivity of the rapid off-response was lowered at long wavelengths; the maximum sensitivity was at 520 nm in most protanopic and protanomalous patients. The mean of the sensitivity of the rapid off-response was significantly lowered at 560 nm and longer wavelengths (P < 0.005), and elevated at 460 and 480 nm (P < 0.05) in protanopic and protanomalous patients, when compared with normal controls. Apparently, there is an abnormality of the photopic function at the receptor level in some cases of protanopia and protanomalia. The rapid off-response could be useful for objective evaluation of protanopia and protanomalia.