The human focal electroretinogram as a function of stimulus area.
Focal electroretinograms to on-off luminance modulation (2.7 Hz) of uniform fields with a different area (144-2.25 deg2) centered on the fovea were recorded in two young normal subjects. The electroretinogram responses typically consisted of an a-wave, a b-wave, a PIII component and a d-wave. The concentric reduction of the test field size caused progressive amplitude decrement of all components, while their response density increased. The spatial summation properties of the b-wave differed from those of the a-wave, PIII component and d-wave so that the relative contribution of the b-wave to the electroretinogram waveform depended on the stimulus area. For a critically small field size, the electroretinogram was dominated by the PIII and d-wave components. Only these two electroretinogram components displayed a density profile that could be compared with that of cone distribution.
Errico
P
P
Institute of Human Physiology, Catholic University, Rome, Italy.
Falsini
B
B
Porciatti
V
V
Cefalá
F M
FM
D000328:Adult; D004596:Electroretinography; D006801:Humans; D008027:Light; D008266:Macula Lutea / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology*