Do visibility and colour recognition isopters relate to the distribution of P alpha and P beta ganglion cells of the human retina?
Early perimetrists recognized that the threshold stimulus diameters for visibility and colour recognition differ markedly in peripheral vision. However, we observed that these diameters are identical at the fixation point. This means that these threshold diameters, when plotted against eccentric visual angle, have unequal slopes, perhaps related to recently reported data on estimated magnocellular and parvocellular neural sampling intervals. We therefore collected perimetric data on eleven normal observers, using red stimuli on the Zeiss Jena Type 1 Bowl Perimeter. It was found that the slopes were steeper than those for supposedly corresponding neural data. This could be explained by taking into consideration that (a) the slow rate of stimulus movement allowed parvocellular contribution to visibility; and (b) the possibility of an enhanced foveal representation in the cortical colour processing areas. The clinical significance of these findings is briefly discussed.
Drasdo
N
N
Department of Vision Sciences, Aston University, Birmingham, UK.
Thompson
C M
CM
D000328:Adult; D003118:Color Perception / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D012160:Retina / Q000166:cytology / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000502:physiology*; D012684:Sensory Thresholds; D014785:Vision, Ocular / Q000502:physiology*; D058609:Visual Field Tests