Even drinking legal limit impairs vision by 30 percent
New research published in the journal Perception suggests that even when we keep our alcohol levels under the legal limit, our vision can be impaired by as much as 30 percent.
To conduct their study, researchers at the Schulich School of Medicine and Dentistry and from Western University in Ontario used a 144-year old optical illusion called the Herman Grid. The Grid, according to one of the scientists, is “basically a grid of black squares on a white background. You see ghost-like dark spots at the intersections of the grid, but they are not actually there. It's the way our visual system processes contrast or brightness differences that creates the illusion.” By staring at the Grid for enough time, the viewer will feel like they had a few drinks.
Next, the researchers had participants drink either nonalcoholic drinks or enough alcoholic drinks to keep them just under the legal limit of 0.08 percent. After consuming their drinks, the participants estimated the contrast of the blobs located on the Grid’s intersections.
For the participants who drank the alcohol, the contrast of the spots in the grid was reduced by 30 percent when their BAC approached the legal driving limit. The researchers noted that this visual impairment would make it very difficult for drivers to distinguish the difference between objects based on lightness and darkness.