Failure of the Visual Pathway During Anoxia

Differentiation, Metabolic Organization, and Viability of the Visual Cell

“…In the studies to be reported, only that fraction of the ERG which occurs within 200 msec, after the "on" of illumina¬ tion was generally measured. Figures 1 to 3 show the main portions of this test for the curarized and artificially ventilated rab¬ bit. It includes the recording of responses provoked in the fully dark adapted animal by light intensities ranging from threshold to the maximum available.…”

“…2-The b-wave of the C3H mouse arises very late after the stimulus but because it is immediately pre¬ ceded by a cornea-negative potential this late ERG differs strikingly from the normal slow scotopic ERG at low stimulus intensity. 3-The responsiveness of the C3H ERG is reduced so that the minimally effective stimuli are at 12 days already about 100 times higher than in controls.…”

“…A preferential reduction of the a-wave consistently was observed whenever any degree of rod abnormality had de¬ veloped after oxygen poisoning or x-radia¬ tion. The b/a ratio, measured from responses to maximal stimuli, and used for correlating the ERG with histology, was increased, for instance, 3 times after x-irradiation which had resulted in exclusive rod degeneration. Such a-wave reduction could appear without a change in b-wave ampli¬ tude.…”

The effect of a moderate level of hypoxia on human color vision

“…Noell and Chinn [33] report that hypoxic deficits occurred earlier for ganglion cell layers (or along the visual pathways) than in the retinal photoreceptors of rabbits. Rabbit ERG's withstood some 20mins of anoxia whereas retinal ganglion cell recordings only survived 5 minutes or less.…”

“…Electrophysiological studies suggest that small ganglion cell fibres are affected more by anoxia than the faster conducting large ganglion cells [33]. Since small ganglion cells are thought to mediate human color vision [22] hypoxia may be expected to depress color mechanisms.…”