How alcohol worsens night vision among drunk drivers

Last Updated 18 June 2014, 09:03 IST

Know why drunk drivers see halos as they zoom past city lights, leading to traffic accidents? It's because alcohol disturbs the tear-film that covers the surface of their eyes, leading to deterioration of vision.

Alcohol consumption markedly impairs night-vision because it increases the perception of halos (luminous circles) and other visual night-time disturbances, a new study shows.

"This is because 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," said principal author of the study Jose Juan Castro from University of Granada, Spain.

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

Moreover, this deterioration of vision is significantly greater in subjects with breath alcohol content in excess of 0.25mg/litre - the legal limit for driving recommended by the World Health Organisation (WHO).

To reach this conclusion, researchers evaluated retina-image quality and night-vision performance following alcohol consumption in 67 participants.

To assess visual performance in low-illumination conditions, the researchers used a visual test known as a "halometer".

The results, published in the Journal of Ophthalmology, showed that following alcohol consumption, the perception of halos and other night-time visual disturbances increased.

Researchers also found that the optical quality of the image the eye produces deteriorated.

"Alcohol consumption and low-illumination conditions are factors present in many traffic accidents, hence people must to be made aware of the effects of alcohol consumption, especially on vision," Castro said.

(Published 18 June 2014, 09:03 IST)

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