When it comes to the effect of cannabis on the eyes, a few popular images come to mind. There’s the tell-tale squint and bloodshot eyeballs that have been a staple of stoner imagery for decades. But what if cannabis could give you night vision? What if smoking weed could make you see in the dark?
How Can Cannabis Give You Better Night Vision?
That’s exactly what new research out of the Montreal Neurological Institute suggests. Their findings show that cannabis acts on nerves related to sight and could give you better night vision. According to the study, cannabis acts directly on the cell’s of the eye’s retina, making them more receptive to light. And the more receptive those cells are, the better the eye can see.
The research is groundbreaking for a few reasons. One is that it turns over a few competing theories about how cannabis affects eyesight. Many people thought smoking marijuana would dilate the eye’s pupils, allowing more light to enter. But other experiments show exactly the opposite. Marijuana constricts the muscles in the eye. Another theory had it that cannabis stimulated nerves in the back of the brain in a place called the visual cortex. But the THC cannabinoid creates its psychoactive effects by binding to the CB1 receptor protein. And there are way more of those proteins in the eye itself than in the brain. So how did researchers discover how cannabis may give you better night vision?
So how did researchers discover how cannabis may give you better night vision?
Testing on Tadpoles
Louis Miraucourt, who led the team from the Montreal Neurological Institute, conducted several tests on the eye tissue of tadpoles. Essentially, researchers dosed the tadpole eyes with cannabinoids. Then, they studied their behavior in different light conditions.
The first test revealed that nerve activity in the retina tissue increased in both high and low light environments. A second test found that cannabis blocked a certain protein that controls the electrical sensitivity of nerve cells on the retina. When cannabis was applied to the eye, the chemical balance in the eye changed, allowing it to be more sensitive to electrical impulses and therefore, much more sensitive to light. A final test put the tadpoles in a dark setting. Tadpoles run from dark spots, which would be hard to see in a dark tank. But Miraucourt and his team found that the tadpoles that were given cannabis were much more successful at avoiding the spots than those who weren’t.
Fishing in the Dark
Although this research on marijuana and eyesight suggests that cannabis may give you better night vision, it’s still unclear whether the findings apply to humans. In many U.S. states, medical marijuana is used to treat glaucoma and other neurological diseases.
Just because the research was done on tadpoles doesn’t mean humans haven’t made their own use of cannabis to see better at night. As The Guardian reports, 25 years ago a scientist in Kingston, Jamaica observed that local fishermen would get high before navigating their boats through dangerous coral reefs at night. It would be an impossible task under normal conditions, but fisherman who drank a rum extract of cannabis had no trouble at all.