Smoking cannabis significantly alters key visual functions, such as visual acuity, contrast sensitivity, three-dimensional vision, ability to concentrate, and sensitivity to glare.
- Contrast sensitivity would be the visual aspect most impacted by cannabis consumption.
- Almost all consumers do not notice cannabis-related visual disturbances.
More than 90% of consumers are totally or almost unaware of it, but cannabis affects vision. Researchers from the Department of Optics at the Spanish University of Granada have studied the effects of its consumption on different visual functions. Their results are clear: smoking cannabis changes them considerably. They were published on January 18 in the journal Scientific Reports.
A significant discrepancy between the real effects and consumer perception
The researchers examined the effects of cannabis consumption on various visual parameters in relation to what consumers perceive. An exhaustive visual test was conducted on 31 cannabis smokers, both when they had not used the substance before and when they were under its effects.
The results showed that, following consumption, many visual aspects are considerably degraded. This affects visual acuity, contrast sensitivity, three-dimensional vision – or stereopsis -, focusing ability and sensitivity to glare. Yet despite this, not all subjects reported worsening vision after smoking cannabis. Indeed, 30% said their vision had not suffered at all, while 65% said it had deteriorated only slightly.
Daily dangers
Contrast sensitivity is, according to the researchers, the visual aspect most impacted by cannabis consumption. According to them, the significant gap between the results and consumer perception indicates the need for awareness campaigns. “This visual deterioration can present a hazard when performing daily tasks”, they concluded.
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