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The Cambridge Colour Test (CCT) was developed to measure hue discrimination in a spatial and luminance noise situation. However, normative data for the CCT are not available since both the original and commercial versions are fairly recent developments. This chapter presents preliminary norms and compares a self-built and the commercial version of the test. The results are compared with the Farnsworth–Munsell 100 Hue test.

The topographical distribution of density and soma size of the retinal ganglion cells were studied in three species of hystricomorph rodents. Flat-mounted retinae were stained by the Nissl method and the ganglion cells counted on a matrix covering the whole retinae. Soma size was determined for samples at different retinal regions. The agouti, a diurnal rodent, shows a well-developed visual streak, reaching a peak density of 6250 ganglion cells/mm 2 . The total number of ganglion cells ranged from 477,427-548,205 in eight retinae. The ganglion-cell-size histogram of the visual streak region exhibits a marked shift towards smaller values when compared to retinal periphery. Upper and lower regions differ in both cell density and cell size. The crepuscular capybara shows a less-developed visual streak with a peak ganglion cell density of 2250/mm 2 . The shift towards small-sized cells in the visual streak is less marked. Total ganglion cell population is 368,840. In the nocturnal paca, the upper half of the fundus oculi includes a tapetum lucidum.The retina of this species shows the least-developed visual streak of this group, with the lowest peak ganglion cell density reaching 925/mm 2 . The total ganglion cell number (230,804) is also smaller than in the two other species. Soma-size spectra of this species are characterized by the presence, in the lower hemi-retina, of very large perikarya comparable in size to the cat's alpha ganglion cells.

This chapter examines the visual performance of Amazonian gold miners and other workers suffering from mercury poisoning. Subjects exposed to mercury displayed a variable degree of spatial vision dysfunction. Both achromatic and chromatic vision were impaired. They had lower achromatic contrast sensitivity and this effect was more pronounced in the medium spatial frequency range. Mercury exposed subjects also had lower red-green and blue-green chromatic contrast sensitivity than control subjects in all tested spatial frequencies.

The distribution of ganglion cells and displaced amacrine cells was determined in whole-mounted Aotus retinae. In contrast to diurnal simians, Aotus has only a rudimentary fovea. Ganglion cell density decreases towards the periphery at approximately the same rate along all meridians, but is 1.2-1.8 times higher in the nasal periphery when compared to temporal region at the same eccentricities. The total number of ganglion cells varied from 421,500 to 508,700. Ganglion cell density peaked at 15,000/mm 2 at 0.25 mm dorsal to the fovea. The displaced amacrine cells have a shallow density gradient, their peak density in the central region is about 1500-2000/mm 2 and their total number varied from 315,900 to 482,800. Comparison between ganglion cell density and areal cortical magnification factor for the primary visual cortex, area 17, shows that there is not a simple proportional representation of the ganglion cell distribution. There is an overrepresentation of the central 10 deg of the visual field in the visual cortex. The present results for Aotus and the results of a similar analysis of data from other primates indicate that the overrepresentation of the central visual field is a general feature of the visual system of primates.