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Marijuana and the Eye: What You Need to Know

Dr. Denise Valenti has been studying marijuana, its impact on eyes and driver safety
Dr. Valenti

There’s an old wives’ tale that marijuana can help with glaucoma. While that hasn’t exactly been proven, Denise Valenti, OD, FAAO, says that there might be some truth to that.

Dr. Valenti specializes in neurodegenerative processes and forensics products for the identification of impairment with marijuana in the visual system. She is one of the leaders in studying the impact of marijuana on the eyes. She currently owns IMMAD-Impairment Measurement Marijuana and Driving, with a focus on education, services, and technology for the responsible use of cannabis.

Interestingly, marijuana inhibits axonal growth, which is considered bad for the developing eye and brain. But that same characteristic “may actually be good for the degenerating or aging eye,” she says.


Marijuana has been shown to reduce intraocular eye pressure (IOP), when used in doses averaging every four hours for control.  Another use may include “Small microdosing for older adults’ cognitive health,” Dr. Valenti says. “But in truth, we do not yet know.”

But “microdosing” is the key term here in weighing the health benefits of cannabis. The higher doses of regular or recreational use, Dr. Valenti says, causes changes in retinal organization. This is not a good thing. “When [marijuana] was originally approved for compassionate eye care, surgery was still archaic,” Dr. Valenti says. “There really were no good treatments. Back then, given a choice of being blind or high, the choice of being high could be considered reasonable.”

Dr. Valenti says it is “essential” for older adults to discuss the use of marijuana with their primary care provider. There may be cardiovascular effects, especially with chronic use. People who want to get high should also consider how they consume marijuana.


Edibles, while avoiding the damage to the lungs, can convert and cause an even “higher” high, so they should be used carefully and in small amounts. Dr. Valenti says inhalation in a vaporizer is “felt to be the best for medicinal use as it is less harsh and very controllable in dosing.”

When it comes to cannabidol (CBD), be careful, she says. “CBD has been shown to elevate eye pressure. However, CBD and THC (the component that causes the high) tend to have opposite effects in the visual system, with what little research and studies there are.”

The old wives’ tale that weed can help with glaucoma has been found in a few human studies. The one most cited by those wishing to have cannabis treat glaucoma, Dr. Valenti says, ignores elevated eye pressure induced by CBD.   Given there are different impacts of different cannabinoids as shown by the THC and CBD examples, Dr. Valenti suggest caution and definitely further research.  .

For those looking to learn more, Dr. Valenti recommends the 2018 Miller and Straiker study. The study “found that CBD elevates IOP” and that “lowering of pressure with THC was gender-specific, with males having greater lowering than females.”

If anything, ingest the natural plant stuff, Dr. Valenti says. CBD has been legalized in many states, but it can be chemically converted into Delta 8—a psychoactive form of THC. Not only can that be dangerous, it is still illegal in some states.

If you’re going to partake, Dr. Valenti says, do your research and talk to your doctor. Better safe than sorry this 4/20. The cannabis culture named 4/20 “weed day.” The day gets its name from the time 4:20 – a great after-school meeting time that became a code term for smoking.

What is IMMAD?

IMMAD is a two-minute objective test for law enforcement to use to determine fitness to drive with marijuana consumption.

To read more news from WO, click here. 

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