Effects of low blood alcohol concentration on visual exploration

Introduction: Visual function is highly influenced by alcohol consumption in many different ways spanning from visual field to stereoscopic vision. In a previous study we investigated the effects of low alcohol concentrations on visual search function using an automatic and non-invasive tool (Tobii 1750). The aim of the present study was to investigate visual ability by a Slide Show task in an “ecological environment”. In the same time attentive function, concentration and memory were explored. These are cognitive and psychomotor functions high related to drive ability. Materials and Methods: Twenty-four healthy volunteers, aged 18-65 years, were recruited. A single dose of alcohol (0.5 g/Kg) or placebo was administered according to a double-blind, cross-over design. Volunteers received the treatment to which they had randomly been assigned and performed the test 0, 30, 90 and 150 min from drinking the beverage. A Tobii 1750 automatic eye-tracker equipped with a proprietary management software was used. The following measures were considered in this study: “number of point of fixation”, “pupil diameter”, “position of the first fixation point”, “coincidence between the first fixation and the longer duration point”, and “extention of explorated area”. A double task (memory recall of words) was applied in the final part of each session. Results: in the alcohol group at 30 min (T1) from drinking the alcoholic beverage we observed a reduction of number of points of fixation. Also the extension of visual area explored was limited at T1, with an increase of coincidence between the prolonged observation point and the area with greatest visual impact. Even the coincidence between time of first fixation and point of longer fixation was greater under the influence of alcohol. At 150 min (T3) from drinking the alcoholic beverage we observed a tendency to direct gaze in the central part of the visual field, particularly this happened for the first fixation point. Furthermore, at 150 min we registered a more pronounced miosis in the alcohol group, in according to our previous study. Conclusions and Discussion: Results confirm that low alcohol levels impair some visual functions; this occurs in absorption phase and in elimination phase of alcohol metabolism. In particular, versus control group, alcohol causes a visual pattern characterized by reduced search ability, static gaze with a clear accommodative effort in last phase. These effects are more evident when the subject is required to perform an adjunctive task with partial distraction of attention from elaborative and cognitive resources. This is a kind of situation quite normal during driving.