Alcohol impairs the night vision

Alcohol impairs eyesight in traffic

31/10/2014

Spanish scientists have found that even small amounts of alcohol negatively affect the night vision. They disturb the tear film of the eye, which increases the light and glare sensitivity at night. In addition to the known limitations of reactivity, this is "another reason for driving under the influence of alcohol to see," as the researchers summarize in their report.

Due to the decreasing reactivity, alcohol is generally a problem in road traffic. According to the Federal Statistical Office, 5 percent of all traffic accidents are directly related to the influence of alcohol, most of which occur on weekends between 8 pm and midnight. The majority of those involved are disco or pub visitors who misjudge their ability to drive.

Ethanol dissolves tear film
However, as it turns out, lack of responsiveness is not the only problem with road traffic alcohol, and eyesight in the dark also plays an important role. This is what Spanish researchers discovered in a study of 67 subjects. They were tested for their vision and photosensitivity after varying degrees of consumption of wine, with clear results: their vision diminished significantly. This is due to the ethanol, which virtually dissolves the fats contained in the tear fluid like a solvent. As a result, the aqueous components of the liquid evaporate faster. In addition, the pupils were greatly dilated in the subjects, which leads to a higher photosensitivity. As a result, traffic signs and contrasts are less recognizable and headlights of oncoming traffic dazzle. From a blood alcohol value of 0.5 per thousand, these effects increase increasingly.

Drunk no longer at the wheel
Therefore, the German Ophthalmological Society (DOG) advises against alcohol in road traffic: "Crucial is that alcohol generally affects our ability to react," says Bernhard Lachenmayr, chairman of the DOG traffic commission. "The fact that ethanol also restricts eyesight only supports the recommendation once again not to get drunk behind the wheel.“

In particular, Lachenmayer points out that reactivity and eyesight change barely perceptible even with small amounts and thus lead to a false assessment of one's own driving ability. "Many bar-goers still consider themselves fit to drive when they have drunk one or two glasses of beer."

Study provides evidence for revaluation of alcohol in road traffic
According to the new findings from Spain, this may be regarded as a questionable assessment. Because the study published in the Journal of Ophthalmology offers insights that allow a better assessment of night vision under the influence of alcohol and thus can be of crucial importance for a reassessment of alcohol in road traffic. (Jp)