Oxygen breathing effects upon night vision thresholds. Rep No 469.

Abstract : Two series of experiments were conducted, --one was concerned with the effects of mask breathing, and the other with breathing 100% oxygen at ambient (sea level) pressure. It was found that the effect of oxygen excess upon rod and cone scotopic threshold is subject to individual variation. Rod and cone scotopic thresholds are only exceptionally affected by breathing near- 100% oxygen for periods up to 140 minutes. When administered at higher pressures, even for periods as short as 20 minutes, the incidence of effects is sharply higher. Rod and cone scotopic thresholds, measured while breathing near-100% oxygen are sensitive to blood sugar levels. Breathing through a mask- demand valve system of the type used in these experiments may cause an elevation of the rod and/or cone scotopic threshold(s) of some individuals, apart from any effect of the inhalant.