If you consume cannabis products on occasion, you may experience a side effect that impacts vision — and yet fail to realize that it’s occurring. That’s according to a new study from the University of Granada, which found multiple vision changes that occurred after consuming the substance, ones that the majority of users didn’t recognize or underestimated.
The new study comes from researchers with the university’s Department of Optics, which looked into the vision changes caused by cannabis and the perception of these changes from users. The research involved 31 participants who used cannabis products, at times evaluating them while sober and at other times while they were under the influence.
Based on the data, the study found that cannabis use impacted all evaluated visual parameters, and not in a good way. Users experienced ‘significantly worsened’ focusing ability, as well as sensitivity to light glares, 3D vision, visual acuity, and contrast sensitivity. Despite the changes, 30-percent of participants said they didn’t perceive any changes in their vision.
In addition, 65-percent of the participants said they experienced only ‘slightly’ worsened vision compared to when sober. The researchers note that the negative effect on vision can pose a risk during various daily activities and that, when combined with users’ lack of awareness of the extent of the changes, educational campaigns on the matter are necessary.
The study notes that despite its continued illegality in many places, cannabis use is on the rise. Understanding the potential health benefits and consequences of the drug has been the focus of a growing body of research, including ones that look into its impact on conditions like Parkinson’s disease, migraine disorders, and more.