Effects of cannabis on visual function and self-perceived visual quality

Abstract

Cannabis is one of the most used drugs of abuse in the world. The objective of this study was to analyze the effects of smoking cannabis on vision and to relate these to those perceived by the user. Thirty-one cannabis users participated in this study. Visual function assessment was carried out in a baseline session as well as after smoking cannabis. We evaluated static visual acuity, contrast sensitivity, stereoacuity, accommodative response, straylight, night-vision disturbances (halos) and pupil size. The participants were also divided into two groups depending on whether they perceived their vision to have worsened after smoking cannabis. A logistic regression analysis was employed to identify which visual test could best predict self-perceived visual effects. The study found that smoking cannabis has significant adverse effects on all the visual parameters analyzed (p < 0.05). Self-perceived visual quality results revealed that about two thirds of the sample think that smoking cannabis impairs their vision. Contrast sensitivity, specifically for the spatial frequency 18 cpd, was identified as the only visual parameter significantly associated with self-perceived visual quality (Odds Ratio: 1.135; p = 0.040). Smoking cannabis is associated with negative effects on visual function. Self-perceived visual quality after smoking cannabis could be related to impaired contrast sensitivity.

Changes in Visual Performance under the Effects of Moderate–High Alcohol Consumption: The Influence of Biological Sex

“…Contrary to the other visual functions analyzed in this work, and considering published studies, there is no agreement as to whether alcohol consumption affects stereopsis, although some authors have found that this deteriorates under the effect of other drugs, such as cannabis [50,51]. According to our results, it is clear that both near and distance stereopsis are highly impaired under the effects of alcohol.…”

Dynamics of the accommodative response after smoking cannabis

“…Although the pupil is also innervated by parasympathetic and sympathetic fibres, we did not find any significant changes in pupil size after cannabis use. This result is consistent with some previous findings, 23 although contradictory results have been published in the literature with regard to the effect of cannabis on pupil size 59,60 …”

“…Cannabis use also seems to alter accommodative function during the steady‐state response, since we found an increased accommodative lag for both target distances, even though this effect was not significant ( p = 0.08). Accommodative lags were similar to those found by a recent study in 31 young cannabis users for the baseline session and after smoking cannabis, although in that study cannabis use generated greater increase in the accommodative lag than in the present work 23 . In general, the lags observed here were comparable to those reported in recent studies employing the same optometer, although those works were not related to cannabis consumption 46,50,52,54 .…”

“…The authors argued that this effect could be due to the sympathomimetic effect of cocaine, nicotine and cannabis, although they admitted that it might depend on other factors, including the type of drug used, the duration of their addiction and gender, but they were unable to analyse these issues. Similarly, one of our recent studies demonstrated that smoking cannabis generated poorer accommodative accuracy (higher lags) 23 …”

“…Similarly, one of our recent studies demonstrated that smoking cannabis generated poorer accommodative accuracy (higher lags). 23 Numerous studies have reported that cannabis use is associated with impaired cognition. Memory deficits are observed in chronic cannabis users; focused, divided or sustained attention is also impaired, showing a dosedependent relationship.…”