Considerations of vision and cerebral function during hypotension.

The currently held theory of preserved consciousness with impaired vision during positive acceleration is based on a maintained intraocular pressure and selective impairment of conduction in the peripheral visual pathway, though the experimental evidence does not wholly support this theory. During hypotension, intraocular pressure follows closely the arterial pressure, and conduction along the optic nerve is preserved as long as the electroretinogram persists. It is proposed that, though the mechanism of visual impairment during hypotension is related to events in the peripheral visual pathway, there are likely to be active forebrain events which preserve consciousness.