Researchers from Spain’s University of Granada report that smoking Marijuana negatively impacts a person’s eyesight, even though most users insist it doesn’t.

Study Finds reports:

The Spanish study reveals smoking cannabis negatively impacts visual acuity, contrast sensitivity, three-dimensional vision (stereopsis), focus, and glare sensitivity. The findings fly in the face of the popular belief that marijuana may help people with eye diseases like glaucoma. Moreover, researchers say over 90 percent of cannabis users believe smoking the substance won’t impair their vision.

In their experiment, study authors examined the effects of smoking marijuana strictly along visual parameters. They then compared those results to the effect users perceive the drug is having on their sight. […]

Results reveal scores for acuity, contrast sensitivity, stereopsis, focus, and glare sensitivity were all significantly lower after smoking marijuana. Despite this, 30 percent of the group still reported their vision hadn’t suffered at all from smoking. Another 65 percent of the participants said they only noticed a slight drop in their vision due to cannabis use.

READ: Smoking marijuana significantly impairs vision — even though most users disagree

The study concluded that with the push to legalize recreational marijuana, that users should be educated on the impact it could be having on their eyesight.

This is not the first study to warn about Marijuana usage:

READ: Scientists show cannabis triples psychosis risk: Groundbreaking research blames ‘skunk’ for 1 in 4 serious mental disorders AND Cannabis users five times more likely to develop schizophrenia than someone who has never smoked it

Studies have also shown that there is a growing perception among young people that Marijuana is safer than alcohol. READ: Perceptions of the relative harmfulness of marijuana and alcohol among adults in Oregon