Aviation-related respiratory gas disturbances affect dark adaptation: a reappraisal.

This study examined the time course of early scotopic threshold sensitivity during dark adaptation under mild to moderate hypoxia, moderate hypocapnia and hyperoxia, measuring detection time displacement relative to normoxia. Cone rod inflection and early rod adaptation were highlighted using progressively dimmer green flash stimuli. Early scotopic sensitivity was significantly delayed by hypoxia and hastened by hypocapnia and hyperoxia. Effects of respiratory disturbance on dark adaptation include temporal shifts of early scotopic sensitivity while human rod photoreceptors appear functionally hypoxic when breathing air at one atmosphere. At night, supplementary oxygen may benefit aircrew visual sensitivity, even at ground level.