Article by Angela Stelmakowich, Growth Op
Awareness campaigns are needed to inform cannabis smokers that using weed can affect their vision to such a degree that it might negatively influence their ability to carry out everyday tasks, new research out of Spain suggests.
A group of investigators from the University of Granada’s Department of Optics found that smoking weed appears to affect the vision of cannabis users, but the vast majority don’t believe that to be the case.
Findings indicate smoking cannabis alters key visual functions such as visual acuity, contrast sensitivity, three-dimensional vision, the ability to focus and glare sensitivity, notes a statement from the university. The adverse effect is significant with regard to visual acuity, contrast sensitivity and nighttime-related visual parameters like the visual-disturbance index and intraocular straylight, the study states.
Even so, the majority of participants reported believing that cannabis use has either no, or only a slight, effect on their vision.
Led by Carolina Ortiz Herrera and Rosario González Anera, findings of the visual trial recently published in Scientific Reports reflect the experiences of 31 — 20 males and 11 females aged 19 to 43 — occasional cannabis users both when they hadn’t consumed any weed in advance and also when they were under its effect.
Despite the worsening of key visual functions after consumption, 30 per cent of subjects reported that their vision had not suffered at all and 65 per cent said it had worsened only slightly.
“Self-perceived visual quality after smoking cannabis could be related to impaired contrast sensitivity,” the study suggests. “We found that this function is objectively worse in those people who subjectively indicate that their vision is worse after using cannabis,” authors write.
“These results, together with the lack of awareness that the participants presented about the visual impairment caused by smoking cannabis, indicate the need to carry out awareness-raising campaigns, as this visual deterioration can pose a danger when performing everyday tasks,” the university reports.
The study acknowledges that data to date on cannabis consumption and vision are inconclusive. Still, authors cite research regarding deterioration in colour vision, static and dynamic visual acuity, adaptation to darkness and glare-recovery time.