Why does weed make your eyes red?
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- Under pressure: lower blood pressure and dilated capillaries
- Do edibles make your eyes red?
- The redder the better?
Among the most common effects of marijuana use (and telltale signs you’ve recently partaken) is red, bloodshot eyes. It’s to be expected, sure, but that doesn’t answer the mysterious question pondered by generations of stoners: why does weed make your eyes red?
For weed novices, the onset of bloodshot eyes could cause a panic-induced internet search asking “ can smoking weed damage your eyes? ” Thankfully, as those who regularly consume cannabis can tell new users, there are no serious health risks associated with your sudden red-eyed circumstance. You’re probably not experiencing an allergic reaction or some bigger complication. Some might poke fun or chastise you for sporting your so-called “ weed eyes ” in public, but otherwise, it’s a completely natural occurrence that transpires after smoking cannabis.
In fact, your eyes turning red has nothing to do with the act of smoking at all.
Under pressure: lower blood pressure and dilated capillaries
After consuming a cannabis-based product (flower, concentrate, edible, etc.), users generally experience an increase in heart rate and blood pressure. This effect is due to the plant’s cannabinoids, which are chemical compounds responsible for some of the therapeutic and medicinal benefits of cannabis, and their initial interaction with the body. This rise in blood pressure and heart rate is comparable to normal physical activities like exercise or sex.
It generally takes about five to ten minutes for users’ heart rates to return to normal and for blood pressure to begin to decrease. As the blood pressure lowers, the blood vessels and capillaries dilate, including the ocular capillaries . The dilation of ocular capillaries causes increased blood flow to the eyes, which results in your eyes turning red and also reduces intraocular pressure.
The dilation of ocular capillaries causes increased blood flow to the eyes, which results in your eyes turning red in the process, and also reduces intraocular pressure. Photo by: Gina Coleman/Weedmaps
In fact, according to Dr. Melanie Bone, a board-certified OB-GYN who practices in West Palm Beach, Florida, “It’s cannabis’ ability to reduce intraocular pressure in the eyes that makes it a potentially viable treatment for glaucoma , a group of eye disorders that causes damage to the optic nerves which can eventually lead to blindness. It also happens to explain why your eyes become bloodshot after smoking cannabis.”
Evidence that the THC found in cannabis can lower intraocular pressure (IOP) is a major reason why many glaucoma patients have attempted to use medical marijuana to treat and relieve symptoms of the disease. It’s important to know that some studies have contradicted or added a caveat to the claim that cannabis is beneficial for glaucoma. For instance, a 2018 study conducted at Indiana University found that cannabidiol (CBD), the non-intoxicating cannabinoid found in marijuana, could potentially worsen the condition by increasing eye pressure . More research into the use of cannabis for glaucoma treatment is needed.
Do edibles make your eyes red?
Similar to smoking cannabis, ingesting edibles could also make your eyes turn red. Again, this depends on the amount of THC consumed. Remember, it’s not the smoke itself that makes your eyes red, but rather the ability that cannabinoids have to lower blood pressure, causing blood vessels and capillaries to dilate.
The redder the better?
The amount your blood pressure is lowered and how red your eyes become depends on the amount of THC you consume.
Tetrahydrocannabinol (THC), the most common cannabinoid in the plant, is responsible for the intoxication associated with smoking cannabis. The greater the concentration of THC in a cannabis product, the stronger the effects and the redder your eyes become.
The greater the concentration of THC in a cannabis product, the stronger the effects and the redder your eyes become.
So, red eyes can act as a sign that your cannabis has a high cannabinoid content (i.e., it’s potent). In other words, if your eyes are noticeably bloodshot after consumption, there’s a good chance you’ve landed yourself some highly potent weed.
Other than being a dead giveaway that you’ve recently consumed cannabis, you have no reason to be concerned about the redness of your eyes. Cannabis-induced eye redness will typically only last a few hours and can easily resolve if you have the right tools at your disposal.
It isn’t a bad idea to have eye drops (or some sunglasses) on hand. Look for eye drop brands that are specifically designed to reduce eye redness. There are other methods that could potentially help combat cannabis-induced bloodshot eyes, including staying hydrated, washing your face and eyelids with cold water, or simply consuming cannabis products with lower THC levels.Ever wonder why using marijuana or cannabis makes your eyes red or bloodshot? Discover why weed gives you bloodshot eyes.
Using Marijuana to Treat Glaucoma
Now with recreational marijuana legalized in Michigan, it’s easier for glaucoma patients to substitute traditional treatment methods for a joint. But does it hurt more than it helps? A University of Michigan expert weighs in.
Marijuana increased in popularity in the mid-1970s when there was interest in cannabinoids for reduction in intraocular pressure (IOP), which is the fluid pressure inside the eye. Now, its usage has increased due to its pleasure-inducing side effects, and behind tobacco, alcohol and caffeine, it is the most widely used drug in society, according to Michigan Medicine ophthalmologist, Theresa M. Cooney, M.D.
Michigan voters took to the polls in November 2008 and voted in favor of the Michigan Medical Marijuana Act (MMA), which protects people with specific medical conditions from penalties under state law who use marijuana for medical purposes. More recently, recreational marijuana has also been legalized in Michigan.
As of 2019, 23 states, including Michigan, have legalized medical marijuana and some people are substituting their glaucoma medication with the drug. But does marijuana help? Cooney says the answer is complicated.
Glaucoma, the second leading cause of blindness in the United States (first for African Americans in the United States), causes optic neuropathy, a progressive loss of visual field and can lead to permanent, irreversible vision loss if not diagnosed and treated appropriately.
A debilitating condition
The MMA allows the usage of prescribed marijuana for “treating or alleviating pain, nausea, and other symptoms associated with a variety of debilitating medical conditions”, which is defined as producing one or more of the following:
Not all cases of glaucoma produce symptoms that classify it as a “debilitating medical condition” like closed-angle glaucoma, according to Cooney. The three types of glaucoma are:
Open-angle (chronic) glaucoma
Closed-angle (acute) glaucoma
Open-angle glaucoma is a chronic medical condition that is generally painless and although vision threatening, it is a slow or non-progressive disease for which medical and surgical treatments are available. Glaucoma eye drops, registered by the Food and Drug Administration (FDA), have long-term, proven efficacy if taken as prescribed.
Closed-angle glaucoma is an acute medical condition with sudden onset, that typically lasts only hours to a few days. It can cause pain and/or nausea because of elevated intraocular pressures. However, once effective pharmaceutical treatment is in place, there are no longer symptoms that would be consistent with a debilitating medical condition, as defined by the MMA.
Secondary glaucoma occurs when an identifiable source causes increased eye pressure that results in optic nerve damage and vision loss. This can be closed-angle or open-angle glaucoma.
Marijuana vs. traditional treatment
There are several classes of drugs proven to be effective as medical treatments for glaucoma. Recent glaucoma drops have also shown effectiveness for up to eight hours.
Aside from medications, there exist various surgery options for patients, such as the Xen gel stent , when a tiny tube is implanted in the eye to preserve vision, and the trabeculectomy, when a piece of tissue is removed from eye to create an opening to drain fluid.
Combining medication and marijuana is not recommended, says Cooney, because “we don’t know how marijuana interacts with traditional treatment methods since there aren’t studies investigating that yet.”
She adds that side effects of these traditional medical therapies are generally known to be considerably more mild than those associated with high-dose marijuana usage.
The effects of marijuana are also variable, since not all marijuana is created equal and it is not FDA approved, which is a serious health concern.
“Marijuana can be laced with anything,” says Cooney. “There are variable potencies of preparation and more than 400 different chemicals involved.”
Marijuana is a Schedule I controlled substance under federal law, meaning that there is a high potential for abuse and there is a lack of accepted safety for its use under medical supervision. It is discouraged from being used in place of any traditional, and studied, treatment options.
The good and the bad
According to Cooney, marijuana can create a 25 percent IOP reduction in 60 to 65 percent of people with or without glaucoma. What exactly causes this within the drug is unknown.
The problem is that IOP reduction lasts from 3 to 3.5 hours. To treat glaucoma effectively, IOP must be controlled around the clock, which likely leads to compliance issues.
“You’d need to smoke eight to 10 marijuana cigarettes a day for them to have the same effectiveness as regular, glaucoma drops,” says Cooney. “That’s 2,920 to 3,650 a year.”
Aside from the high, marijuana can substantially reduce blood pressure, which is a systemic problem. Reducing blood flow to the optic nerve means increasing susceptibility to optic nerve damage, which worsens glaucoma.
Decreased blood pressure is present within an hour, but in some who experience postural hypotension with hypertension, it can be as quick as 10 to 15 minutes.
Another systemic problem: smoking marijuana cigarettes can cause cardiac palpitations within two to three minutes, which will only return to normal after 90 to 120 minutes.
More apparent than physical alterations are the psychotropic effects that can cause euphoria, dysphoria and disruption of short term memory. These effects prevent individuals from safely driving, operating heavy machinery or functioning at maximum mental capacity.
Because marijuana is not filtered, neither are the cigarettes. Long-term usage can cause emphysema-like respiratory changes because of their release of tar, carcinogens and other volatile materials.
“There’s a higher concentration of these carcinogens in marijuana than tobacco, which increases your cancer risk” says Cooney.
Other long-term side effects include:
Hormonal changes, which can increase the risk of poor pregnancy outcomes
Impaired immune system responses
Impaired motor coordination
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