Pattern electroretinograms were elicited in 13 normal eyes by half-field checkerboard stimulation of nasal-temporal and upper-lower retinal areas. With nasal-temporal visual half-field stimulation the p-q component amplitude of the nasal hemiretina was significantly larger than that of the temporal hemiretina. With upper-lower visual half-field stimulation the amplitude was significantly larger for the upper than for the lower hemiretina. No significant differences were found with respect to the component latency. Finding the p-q amplitude of the pattern electroretinogram to be closely related to the distribution of nerve cells in the innermost retinal layer supports the conclusion that the pattern response is generated in the more proximal retinal layers including the retinal ganglion cells.
Transient electroretinograms to a reversing color-contrast checkerboard pattern (P-ERG) were recorded in a protanomalous, a deuteranomalous, and a normal observer. Alternate monochromatic checks were of constant wavelength (630 nm red-531 nm green), while the relative energies were varied systematically. When changing the radiance ratio 630 nm-531 nm of the stimulus, the normal subject exhibited a P-ERG to all stimuli with only a relative amplitude minimum at a distinct radiance ratio, whereas the color-deficient observers failed to show a P-ERG at some color contrast 630 nm-531 nm, the radiance ratio of which was different in the protan and deutan. From the radiance ratio of color contrast for the smallest potential in the normal observer, we conclude that the green- and red-sensitive cone mechanism provides a difference signal which generates the response. The data from the color-deficient observer support the view that color discrimination in protans and deutans is reduced because the input of one type of photoreceptor is missing.
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