Cannabis use may affect certain aspects of visual function, notably increasing light sensitivity and eye-related symptoms, a Moroccan study suggests. Researchers say the findings highlight the importance of regular eye check-ups and call for further studies to better understand cannabis's long-term effects on vision. DR ‹ › Cannabis consumption may affect certain aspects of visual function among Moroccan users, according to a new local study. Published this January in the peer-reviewed journal Psychoactives, the study combines self-reported visual perception with clinical eye assessments to explore how cannabis use may influence eyesight in Morocco, one of the world's historic cannabis-producing countries, yet a setting where the health effects of consumption remain poorly documented. «Our results showed that using cannabis could have significant adverse effects on visual functions», the researchers wrote. The findings were based on a cross-sectional study conducted between March 2022 and April 2023 in Marrakech, with 95 cannabis users taking part. Sensitivity to daylight Among the study's most striking findings, more than two-thirds of participants reported increased sensitivity to daylight after cannabis use. Over 90% of participants said they experienced at least one eye-related symptom, most commonly red eyes and drooping eyelids. At the same time, most users reported no blurred vision at near or far distances, suggesting that cannabis-related visual effects may be subtle rather than immediately disabling. The researchers collected data in two phases: participants first completed a hetero-administered questionnaire covering socio-demographic characteristics, patterns of cannabis and other substance use, and eye health history. They then underwent a series of visual examinations assessing visual acuity, overall visual function, ocular health, and lateral and vertical phoria at both near and far viewing distances. The sample was predominantly male, with men accounting for 87.4% of participants. The average age was 33.6 years, ranging from 18 to 67. Most participants were single, lived with their families, and reported stable living conditions. Educational and professional backgrounds varied, though the majority were either employed or students. Increased night vision among hashish users In terms of consumption patterns, hashish was the most commonly used form of cannabis, and smoking was the sole mode of use reported. The average age of first cannabis consumption was 17.5 years, pointing to early initiation. More than half of the participants reported a family history of cannabis use, often involving close relatives. An unexpected result was that about one third of participants perceived an improvement in night vision, particularly among hashish users. The authors note that this finding echoes a rare Moroccan case report published in 2004, which also described improved night vision in a cannabis user. However, they caution that such perceptions are subjective and do not necessarily correspond to objective visual enhancement. Clinical testing showed that most participants exhibited exophoria at both near and far distances, while vertical phoria remained normal across the entire sample. In conclusion, the authors stress the importance of regular eye examinations for cannabis users and call for future longitudinal studies using objective measures to better understand the long-term impact of cannabis on vision.
