CBD, short for cannabidiol, has become a buzzword in both the scientific research community and the world of holistic wellness. But why is CBD so talked about?
Many people choose CBD products as a natural way to improve their overall health and find relief from various issues. It's legal in all US states, including the District of Columbia, and is praised for being generally safe. People use it for everything from managing pain and sleep to easing anxiety.1
While the use of CBD has exploded, emerging research focuses on its potential therapeutic impact on targeted health concerns, including eye health. Preliminary research and anecdotal evidence have sparked discussions on how CBD benefits vision issues and whether CBD oil’s eye side effects pose any risks.
What is CBD?
CBD is one of over a hundred cannabinoids found in the cannabis plant. Cannabinoids like CBD interact with the body's endocannabinoid system (ECS), our body’s messaging network of receptors and enzymes that control various physiological processes, including mood, pain, appetite, and sleep.2
Unlike THC (DeltaΔ-9-tetrahydrocannabinol), the intoxicating compound in cannabis responsible for the “high” feeling, CBD is non-intoxicating, so users get relief without feeling spacy or euphoric. The risk of overdose is practically non-existent – no one has ever overdosed on CBD or any natural form of cannabis. These positive characteristics have boosted CBD’s growing popularity among individuals seeking the therapeutic benefits of cannabis without the intoxicating effects.
While more is needed, preclinical research seems to support the people’s choice. It has shown promise for a diverse range of health conditions, including psychotic disorders, anxiety, epilepsy, sleep disorders, cardiovascular diseases, diabetes, pain management, and even cancer treatment.3
Only one pharmaceutical CBD drug, Epidiolex, is FDA-approved for specific conditions. Still, CBD-infused products (including lip balms, beverages, vapors, edibles, topicals, essential oils, and so on) are widely available over the counter. However, individuals should take caution as CBD may interact with certain prescription medications.4
The medical community confirms the favorable safety profile of CBD. It is typically well-tolerated, with minimal risk of abuse potential. In studies, the most common side effects include sedation, loss of appetite, diarrhea, fatigue, and sleep disturbances.5
Research has demonstrated over the years that CBD may have potential in the medical world. With a focus on eye health, researchers are looking into the benefits and possible side effects of CBD use and vision.
CBD Oil's Side Effects on the Eyes
Some people experience eye-related side effects when using CBD oil. While CBD is known for its potential therapeutic properties, how it impacts ocular health and vision is an emerging discussion and part of ongoing research.
Reports from CBD users prompt questions about CBD oil and its potential impact on the eyes, optic nerve, and vision. Some patients report irritated and dry eyes as a side effect of use.
For some, dry eyes may result from allergic reactions to CBD or components in CBD oil. Although rare, allergy symptoms can manifest as eye redness, itching, or swelling. If allergic reactions following the use of a CBD product become severe or painful, a healthcare professional should review the use.
In doses of CBD that may have some amounts of THC, mild intoxicating effects, although less pronounced than THC alone, may influence perception and indirectly affect vision in some individuals. These effects can vary depending on factors such as dosage and individual sensitivity.
Some side effects may not be immediately noticeable to the user. Scientific research has been conducted on the side effects of CBD as they relate to other medical conditions or treatments.
The relationship between CBD and intraocular pressure (IOP) is a primary area of interest to ophthalmologist physicians who treat eyes. Inside the eyeball, this balance of fluid under pressure maintains the perfect shape of the eye. If this ocular or eye pressure is too low or too high, it can cause problems with vision.
For example, elevated IOP is a risk factor for glaucoma, which can lead to optic nerve damage and vision loss. Initial CBD impact studies have conflicting results. One report suggests that CBD may have the potential to raise IOP, which could be detrimental for individuals with glaucoma.6 Yet another research team found no proof that CBD had any effect on eye pressure.7 CBD's long-term safety and efficacy in glaucoma management require further investigation.
CBD does influence blood pressure and blood flow. Changes in blood pressure can affect the optic nerve and overall eye health, especially in individuals with existing vision problems. Since CBD may lower blood pressure, the significance of these changes on vision and eye conditions is being studied.8
CBD vs THC for Glaucoma
Concerns about CBD and eye health center around intraocular pressure (IOP), a primary cause of glaucoma. Glaucoma is a group of eye conditions that cause damage to the optic nerve, often resulting from unmanaged and elevated IOP. It’s a significant cause of blindness, affecting around 3 million people in the United States alone.
If the eye fluid pressure gets too high, this elevated IOP can damage the optic nerve, which transmits images to the brain. If the increased pressure continues, glaucoma can lead to permanent vision loss.
One study found that CBD might interfere with the IOP-lowering effects of THC. In this 2018 study on mice, CBD independently raised the IOP while it inhibited the positive THC effect of lowering pressure.5 The study suggests that researchers need to look more into whether CBD raising ocular pressure could be a harmful side effect, especially with long-term use.
On the flip side, other studies show that scientists don’t have a clear answer on whether CBD increases, decreases, or has any effect on IOP. CBD is recognized for its antioxidant, anti-inflammatory, and neuroprotective properties, which could be beneficial in protecting the eyes and slowing down the progression of glaucoma.3 Despite these unknowns, ongoing research looks into CBD’s potential benefits for glaucoma and other eye conditions like eye inflammation or macular degeneration.
THC’s ability to reduce ocular pressure was discovered in the early 70s, with better results than any other available glaucoma treatments at that time. This IOP-lowering effect makes THC a potential option for those seeking relief from glaucoma. THC and lab-created synthetic cannabinoids are being used to reduce eye pressure in glaucoma patients significantly.9
When considering treatment options for glaucoma, your ophthalmologist should be your guide. If cannabinoid therapies are an option, THC or synthetic cannabinoids show proven results in lowering IOC. Current studies conclude that CBD may not be effective for this.
However, CBD is recognized for its antioxidant, anti-inflammatory, and neuroprotective properties, which could be beneficial in protecting the eyes, slowing down glaucoma progression, or treating other eye conditions.6
Does CBD Make Your Eyes Red?
A common side effect of cannabis use is red eyes, but does CBD share this characteristic? The short answer is generally no — CBD alone does not typically cause red eyes. The redness in the eyes associated with cannabis use has been primarily linked to THC due to its interaction with cannabinoid receptors in the brain.
THC lowers blood pressure, which leads to the dilation of blood vessels and capillaries throughout the body, including the tiny blood vessels in the eyes.10 These tiny capillaries swell, resulting in redness or bloodshot eyes and dilated pupils. While CBD does have vasodilatory properties, it typically does not induce red eyes in the same manner THC does.7
However, it’s important to note that many CBD-dominant cannabis or CBD products on the market may contain trace (or higher) amounts of THC, depending on the source and extraction method.11 Therefore, while pure CBD may not cause red eyes, using a CBD product with even a tiny amount of THC could lead to redness, especially in individuals sensitive to THC.
Choosing "THC-free" products and reviewing third-party lab test results to verify the THC content is a good idea for those seeking CBD products without the risk of red eyes. A healthcare professional may also be able to suggest high-quality CBD products that align with your needs and preferences.
Weed's Effects on Vision
Cannabis does affect vision, both in what you see and how well you see it.
A study published in Nature tested a wide variety of visual assessments, and the consumption of THC showed a negative result in every category vs. the pre-consumption baseline. Participants in the study were asked if cannabis affected their vision, and more than 32% said cannabis use had little or no impact on their vision and eyesight. However, study test results on participants while they were under the influence of cannabis told a different story.
Cannabis use clearly worsened stereo acuity, the eye’s ability to see in three dimensions. This lack of depth perception becomes noticeable in everyday activities, like understanding how far away a stop sign is or gauging the distance to a basketball hoop. Walking a trail, navigating uneven terrain, or obstacles on a city sidewalk might be difficult.
Static visual acuity, the vision needed to see a non-moving object, like an eye chart clearly, was also reduced. Additionally, cannabis users were found to be more sensitive to glare, which can be problematic when driving at night or in bright conditions.
On the exterior surface of the eye, cannabis has been shown to reduce tear production, leading to drier eyes. Combined with its anesthetic effect that reduces corneal lens sensitivity, this results in less frequent blinking. Consequently, the liquid tear coating doesn’t cover the eye smoothly, creating an uneven surface to the eye that bends the light and distorts vision.12
In close-up work, like reading a computer screen or assembling small parts, accommodative lag or difficulty focusing on near objects can make things blurry. This potentially occurs when the cannabinoids reach the CB1 receptors in the eye’s retina, where light is translated into nerve signals the brain interprets as altered images.13
THC, the intoxicating component of cannabis, can temporarily alter visual perception, leading to heightened colors, increased light sensitivity, and altered visual acuity. These effects are typically short-lived and subside as the intoxicating effects of THC wear off. But does CBD have the same impact on vision as THC-rich cannabis?
When it comes to CBD, the non-intoxicating cannabinoid, the impact on vision is less clear. While CBD doesn’t induce the same changes in sight associated with THC, the research that suggests it may affect intraocular pressure is potentially concerning for individuals with glaucoma or other eye conditions.
One case tells of a 57-year-old woman who became hyperopic or farsighted after taking CBD daily, suggesting that there might be a link between CBD consumption and changes in vision.14 However, this is a single case; more extensive clinical research is needed to draw definitive conclusions.
CBD's Side Effects on the Eyes: Balancing the Risks
While CBD may offer many potential benefits, it isn’t without side effects. The FDA warns CBD has the potential to cause harm without warning symptoms. For instance, some research suggests that CBD may cause an increase in some liver enzymes, which may be a sign of liver damage, but the research remains inconclusive. Still, this risk underscores the importance of monitoring and consultation when considering CBD, especially for those with pre-existing liver conditions.
Additionally, CBD can interact with other medications, potentially altering their effects and leading to serious side effects. Another area of concern is the potential impact of CBD on male reproductive health. Studies conducted on animals have shown that exposure to CBD can lead to male reproductive toxicity. This means it could cause damage to fertility in males or change in sexual function.15
Although less severe, CBD may cause immediate side effects upon use. Some individuals might experience changes in their alertness, becoming drowsy or sleepy. Gastrointestinal symptoms, like diarrhea or decreased appetite, are not uncommon.5 Moreover, mood changes, especially feelings of irritability and agitation, have been reported by some CBD users. Fortunately, these side effects tend to improve once CBD consumption is stopped or the dosage is reduced.
A surprising concern in the safety of CBD comes from the actual products. The CBD market is largely unregulated. Untested products may have mislabeled CBD content (or none at all). Potency, therapeutic benefits, and purity claims are suspect without third-party testing.16
For example, companies that market CBD eye drops are not FDA-approved, and there is no regulation on producing these products. Using untested and unregulated products on sensitive eye tissue may have dangerous and unwanted side effects. In fact, even companies with FDA approval face contamination concerns, as over seven different brands of eye drops are currently being recalled by the FDA over unsanitary conditions in the production facility.
To ensure the proper steps are taken for eye-related and all health concerns, speak with a healthcare provider or ophthalmologist before adding CBD into a wellness routine. Combined with regular check-ups, your healthcare provider can oversee your safe treatment and follow-up for optimal eye health.
References
- Moltke J, Hindocha C. Reasons for cannabidiol use: a cross-sectional study of CBD users, focusing on self-perceived stress, anxiety, and sleep problems. Journal of Cannabis Research. 2021;3(1). doi:https://doi.org/10.1186/s42238-021-00061-5
↩︎ - Lu HC, Mackie K. An Introduction to the Endogenous Cannabinoid System. Biol Psychiatry. 2016;79(7):516-525. doi:10.1016/j.biopsych.2015.07.028
↩︎ - Peng J, Fan M, An C, Ni F, Huang W, Luo J. A narrative review of molecular mechanism and therapeutic effect of cannabidiol (CBD). Basic & Clinical Pharmacology & Toxicology. 2022;130(4):439-456. doi:https://doi.org/10.1111/bcpt.13710
↩︎ - Brown JD, Winterstein AG. Potential Adverse Drug Events and Drug–Drug Interactions with Medical and Consumer Cannabidiol (CBD) Use. Journal of Clinical Medicine. 2019;8(7):989. doi:https://doi.org/10.3390/jcm8070989
↩︎ - Millar SA, Maguire RF, Yates AS, O’Sullivan SE. Towards Better Delivery of Cannabidiol (CBD). Pharmaceuticals. 2020;13(9):219. doi:https://doi.org/10.3390/ph13090219
↩︎ - Miller S, Daily L, Leishman E, Bradshaw H, Straiker A. Δ9-Tetrahydrocannabinol and Cannabidiol Differentially Regulate Intraocular Pressure. Investigative Ophthalmology & Visual Science. 2018;59(15):5904-5911. doi:https://doi.org/10.1167/iovs.18-24838
↩︎ - Aebersold A, Duff M, Sloan L, Song ZH. Cannabidiol Signaling in the Eye and Its Potential as an Ocular Therapeutic Agent. Cellular Physiology and Biochemistry. 2021;55(S5):1-14. doi:https://doi.org/10.33594/000000371
↩︎ - Baranowska-Kuczko M, Kozłowska H, Kloza M, et al. Vasodilatory effects of cannabidiol in human pulmonary and rat small mesenteric arteries: modification by hypertension and the potential pharmacological opportunities. J Hypertens. 2020;38(5):896-911. doi:10.1097/HJH.0000000000002333
↩︎ - Mack A, Joy J. MARIJUANA AND GLAUCOMA. In: Marijuana as Medicine? The Science beyond the Controversy. National Academies Press (US); 2000. https://www.ncbi.nlm.nih.gov/books/NBK224386/
↩︎ - Latif Z, Garg N. The Impact of Marijuana on the Cardiovascular System: A Review of the Most Common Cardiovascular Events Associated with Marijuana Use. Journal of Clinical Medicine. 2020; 9(6):1925. https://doi.org/10.3390/jcm9061925
↩︎ - Spindle TR, Cone EJ, Goffi E, et al. Pharmacodynamic effects of vaporized and oral cannabidiol (CBD) and vaporized CBD-dominant cannabis in infrequent cannabis users. Drug Alcohol Depend. 2020;211:107937. doi:10.1016/j.drugalcdep.2020.107937
↩︎ - Ortiz-Peregrina S, Ortiz C, Casares-López M, Jiménez JR, Anera RG. Effects of cannabis on visual function and self-perceived visual quality. Scientific Reports. 2021;11(1). doi:https://doi.org/10.1038/s41598-021-81070-5
↩︎ - Labhishetty V, Cholewiak SA, Roorda A, Banks MS. Lags and leads of accommodation in humans: Fact or fiction? Journal of Vision. 2021;21(3):21. doi:https://doi.org/10.1167/jov.21.3.21
↩︎ - Ali A, Gupta PK. Change in Refractive Error Associated With the Use of Cannabidiol Oil. Cureus. 2021;13(4):e14434. Published 2021 Apr 12. doi:10.7759/cureus.14434
↩︎ - Payne KS, Mazur DJ, Hotaling JM, Pastuszak AW. Cannabis and Male Fertility: A Systematic Review. J Urol. 2019 Oct;202(4):674-681. doi: 10.1097/JU.0000000000000248. Epub 2019 Sep 6. PMID: 30916627; PMCID: PMC7385722.
↩︎ - Hazekamp A. The Trouble with CBD Oil. Medical Cannabis and Cannabinoids. 2018;1(1):65-72. doi:https://doi.org/10.1159/000489287
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The information in this article and any included images or charts are for educational purposes only. This information is neither a substitute for, nor does it replace, professional legal advice or medical advice, diagnosis, or treatment. If you have any concerns or questions about laws, regulations, or your health, you should always consult with an attorney, physician or other licensed professional.
