Drinking impairs night vision

Ethanol from alcoholic drinks passes into the tear and disturbs the outermost layer of the tear-film – the lipid layer – facilitating the evaporation of the aqueous part of the tear.

In an eye with a deteriorated tear-film, the quality of the image that forms in the retina also deteriorates, researchers found.

In a study published in the international Journal of Ophthalmology, the authors evaluated retina-image quality and night-vision performance following alcohol consumption in a sample of 67 subjects.

To assess visual performance in low-illumination conditions, the researchers used a visual test known as a “halometer,” developed in the Laboratory.

This enabled them to quantify the level of night-vision disturbance in the form of, say, halos around bright lights, perceived by the subjects.

The results showed that following alcohol consumption, the perception of halos and other night-time visual disturbances increases and the optical quality of the image the eye produces deteriorates.

The deterioration in vision is significantly greater in subjects with breath alcohol content over 0.25mg/litre, the legal limit for driving recommended by the World Health Organization, researchers said.