Visual Function Impairments Result From Alcohol, Cannabis Use

Alcohol consumption and cannabis smoking impair visual functions including visual discrimination capacity, stereopsis, and contrast sensitivity, according to a study published in Experimental Eye Research.  

Researchers conducted a study of 64 healthy volunteers (mean age [SD], 24.8 [4.4] years; 37 men). All participants underwent several randomized experimental sessions during which distance stereopsis, retinal straylight, visual discrimination capacity, and contrast sensitivity were assessed. Cannabis smokers (n=30) underwent assessments at baseline and 20 minutes after smoking a cannabis cigarette. Alcohol users (n=34) underwent assessments at baseline, following low alcohol consumption (alcohol 1; 300 mL red wine), and after a session of moderate to high alcohol consumption (alcohol 2; 450 mL red wine).

According to the report ,cannabis and alcohol use impaired all visual functions, particularly in members of the cannabis and alcohol 2 groups. Straylight was higher, binocular visual disturbance index increased, and stereopsis and contrast sensitivity worsened in all cohorts following alcohol or cannabis ingestion compared with baseline. Participants in the alcohol 2 group experienced the highest deterioration of all variables compared with participants in the other cohorts except for retinal straylight and distance stereopsis. Sex and age affected these visual changes, with women experencing worse visual impairment than men, the researchers note. 

The researchers highlight the importance of identifying these visual impairments stating, “[t]hese results are of importance since it has been reported that these visual functions are involved in visual daily tasks, such as driving performance, and more so considering that alcohol and cannabis use is frequently detected among drivers.”

Study limitations include difficulty in differentiating between visual and psychomotor impairment and failure to control for cannabis type. 

Disclosure: This research was supported by multiple sources. Please see the original reference for a full list of disclosures.