Abstract
The effects of alcohol on the central nervous system are widespread. Many of these effects are mediated by changes in the transmission properties of neurotransmitters, including those operating in the retina. Recent findings suggest that alcohol might influence early visual processing (Arden & Wolf, 2000) and it has been proposed that alcohol might induce a state akin to dark adaptation within the retina (Bernhard & Skoglund, 1941; Ikeda, 1963). However, that evidence was indirect. Alcohol has also been shown to have retinal effects beyond the photoreceptors (Bäckström, 1977). To investigate these proposals psychophysically we measured dark adaptation functions following alcohol consumption in two experiments. In a third experiment we used the increment threshold procedure of Hood and Greenstein (1982; 1990) to examine the possibility that alcohol might affect retinal gain control rather than sensitivity. Individuals were tested under both placebo and alcohol conditions (approx. BAC .08 ml/dl). In Experiment 1, thresholds for the detection of a 2 deg circular patch, located 4 deg in the periphery, was measured over a 25 min period following a 3 min bleach at 6250 cd m2. There were no effects of alcohol on either the rod or cone portion of the curve. In Experiment 2, the cone function was measured for a 2 deg white foveal target following bleaching at three different levels. Again, there were no effects of alcohol. In Experiment 3, thresholds were measured for a 60 min arc target superimposed on a circular 7 deg field whose luminance was varied over 4 log units. No differences were demonstrated between alcohol and placebo conditions. These data indicate that alcohol at these dose levels does not affect the recovery of visual sensitivity in the dark, nor gain control at the retinal level.