Change in Refractive Error Associated With the Use of Cannabidiol Oil This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits CBD is a chemical found in marijuana that is considered medicinal, and it has been advertised as a treatment for many issues, including glaucoma. Learn why CBD does not actually work well for eye treatment. CBD and glaucoma can be a dangerous combination. In fact, CBD products can worsen your condition! It's no substitute for medical treatment.
Change in Refractive Error Associated With the Use of Cannabidiol Oil
This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Cannabinoid (CBD) products have gained popularity since their legalization in 2018, causing a plethora of unregulated CBD products to be sold in the United States. These products are available in various combinations for topical and oral consumption, claiming credit for potentially improving various diseases. In this report, we present a newfound case reporting a shift in refraction that may be associated with the regular use of CBD oil supplements.
A 57-year-old woman with a history of diabetes mellitus type 2, hyperlipidemia, obstructive sleep apnea, with no change in medications, diet, or lifestyle was found to have a hyperopic shift in vision with the recent daily addition of CBD oil intake.
This case report highlights the possible association of CBD oil and vision changes after regular consumption of CBD oil in an otherwise stable patient. Further study is required to understand the mechanisms of CBD oil-associated shift in refractive error. Because the patient is diabetic and the refraction shift was hyperopic, other etiologies, such as un-noted lenticular change, cannot be ruled out. CBD products are unregulated and marketed in many mixed forms, and thus can cause unforeseen effects on susceptible individuals. This warrants Food and Drug Administration (FDA) regulation of such products and extensive research before considering them for therapeutic usage.
Cannabis, or marijuana, has been utilized in psychogenic therapy for hundreds of years. Over the past few decades, it particularly has a newfound use in pain medicine, neurology, oncology, gastroenterology, and ophthalmology [1-2]. Recently, cannabinoid (CBD) oil has been immensely used as supplements and in beverages after the passing of the Hemp Farming Act (HFA) in 2018, which legalized hemp-derived products in the United States. This has allowed commercial companies to produce and sell unregulated CBD oil products without US Food and Drug Administration (FDA) approval. Each product of CBD is potentially unregulated as an uncontrolled substance with varying concentrations, variance in the quality of hemp varieties, and lipid oxidation profiles . Without regulation and medical guidance, CBD oil products can cause severe side effects . We present an isolated case of a patient who reported gradual improvement in myopic vision after starting cannabidiol (CBD) oil for the past few weeks and reversal to original myopic refraction after the discontinuation of CBD oil. To our knowledge, this is the only case report that presents a hyperopic shift in association with cannabidiol oil intake in the English language ophthalmic literature.
A 57-year-old, white female presented to the optometry clinic with eye strain and a gradual decrease in her vision for the last three weeks. She reported her eye strain was somewhat relieved after she removed her glasses. Her medical history was remarkable for obstructive sleep apnea, hyperlipidemia, and polyneuropathy secondary to continued uncontrolled type 2 diabetes (most recent hemoglobin A1c = 12.8%), osteopenia, and restless legs syndrome. Her social history included cigarette smoking (seven cigarettes a day with a five-pack-year history). She denied the use of alcohol or recreational drugs. Her ocular history pertaining to trauma or any surgery was negative. Additionally, she noted having no other symptoms such as headache, dry eyes, double vision, vision loss, spots, or threads in her vision.
On examination, her visual acuity (VA) with her habitual glasses was 20/60 in the right eye (OD) and 20/70 in the left eye (OS), pin holed to 20/40 OD and 20/40 OS. The pupils were round and reactive to light OU, with no relative afferent pupillary defect. External examination, extraocular muscle movements, and counting finger visual field tests were normal. Her intraocular pressure was 16 mmHg in the right eye and 17 mmHg in the left eye, measured with a tonopen. The dilated fundus examination revealed rare cotton wool spots, microaneurysm, dot-blot hemorrhages, and vascular attenuation consistent with moderate, non-proliferative diabetic retinopathy in both eyes without any signs of macular edema (Figure (Figure1). Her 1 ). Her optic cups appeared normal with no signs of glaucoma. Given her decrease in vision and clinical presentation of non-proliferative diabetic maculopathy, we decided to run a macular optical coherence tomography (OCT) scan (Figure (Figure2). 2 ). The fovea showed a normal contour, no central macular edema, and an average central retinal thickness of 275 µM OD and 273 µM OS.
Color fundus photographs of the right eye (A) and left eye (B) with non-proliferative diabetic retinopathy
Cotton wool spot (thin arrow), dot blot, and exudates (thick arrow)
Fovea shows normal contour with no central edema; average central macula thickness of 275 µM OD and 273 µM OS
On refraction, her manifest refraction had shifted from her habitual of -2.25 D sphere to -0.75 D in the right eye and from a habitual of -2.00 D to -0.75 D sphere in the left eye. Her new corrected VA in the right eye was 20/25 and 20/25 in the left eye, and a new pair of prescription glasses were made. This new information of hyperopic shift led us to systemically review her medications for possible associations.
Her medications included multivitamins, dulaglutide, canagliflozin, sitagliptin-metformin, lisinopril, gabapentin, pramipexole, clotrimazole-betamethasone, cyclobenzaprine, glucosamine sulfate, zolpidem, cetirizine, ranitidine, and magnesium oxide. In addition to the above, over the past eight weeks, she had started taking 750 mg of peppermint-flavored Full Spectrum CBD Oil (HempWorx, MyDailyChoice, Las Vegas, Nevada), 12 drops twice a day for restless leg syndrome. The patient reported having improved sleep but associated gradual blurry vision which made her visit the optometry clinic.
At the three and six-month follow-ups, the patient’s refraction was re-assessed, and her improved VA remained stable with no report of blurry or worsening of vision, headache, or eye strain. The patient continued to take CBD oil regularly as before and claimed her improved vision to the intake of CBD oil. The patient additionally reported no significant change in diet, lifestyle, and medication and reported her new glasses to be “perfect.” At the nine-month tele-visit follow-up, the patient ran out of CBD oil and thus had to stop taking CBD oil for three to four weeks. Within three weeks of stopping the CBD oil, the patient again noted a gradual worsening of her vision. The patient tried her old prescription lenses with -2.25 OD and -2.00 OS refractive error correction and reported seeing clearly. She had reverted to her original myopic state after stopping the CBD oil.
Based on the patient’s history and ocular examination, there is a clear hyperopic shift in the patient’s refraction after initiation of the CBD oil supplement and its reversal after stopping the CBD oil. Her refractive error remained unchanged while she was on the CBD oil supplement and attests to the use of CBD oil regularly as she finds relief from her restless leg syndrome. Possible etiologies of her refractive shift include the patient’s status of diabetes mellitus type 2, medication history, and her recent use of CBD oil .
Based on the exam and imaging, our patient had classic diabetic retinopathy (last HbA1C 12.8%) with no significant macular edema. Myopic shifts in vision are reported in about 4% of the diabetic patient population, however, hyperopic shifts are reported even less often. Myopic and hyperopic shifts have been traditionally thought to be due to hyperglycemia and hypoglycemia, respectively, but recent studies have suggested hyperopic shifts can also occur due to hyperglycemia . The hyperopic type of refractive shift in an uncontrolled diabetic patient has been mostly attributed to the changes in the refractive index of the lens due to fluctuations in water distribution [7-9]. In the current patient, the timing of the onset of refractive change, along with her chronic state of uncontrolled diabetes (based on her last three years of high Hb A1C numbers), is unlikely due to her hyperglycemia, especially when associated with the change in vision over three weeks of time after the initiation of CBD oil. Interestingly, her refractive shift was stable while she was on the CBD oil and reverted to her original myopia after she stopped taking the CBD oil.
The association of vision change after the start of the CBD oil cannot be ruled out as one of the plausible causes. The authors are aware that this is an isolated case report where the patient clearly related her gradual change in vision after starting the CBD oil drops twice daily for six weeks. While the mechanism by which CBD oil affects refractive error is still an area for further exploration, CBD has been shown to regulate blood flow in retinal vessels and help in reducing neurotoxicity, oxidative stress, and blood-retinal barrier breakdown. The possible inhibition of p38 MAP kinase may also be a possible theory for the hyperopic shift [10-12]. Effects of cannabinoids on the anterior segment of the eye are also multiplex, and some studies indicate decreased corneal endothelial density . Further studies will be needed to assert the findings from this isolated presentation of the case to better understand the role of CBD oil in refractive errors of the eye, especially in a diabetic condition.
We present a case where a woman taking CBD oil orally for six weeks on a regular basis was found to have an improvement in myopia. In addition, her hyperopic shift reverted to her original myopic vision once she stopped taking her CBD oil. To our knowledge, this is the first case of CBD oil in association with a hyperopic shift. The mechanisms by which her VA improved are uncertain and can vary from possible corneal changes to retinal vasculopathy. Hyperopic shift due to her diabetes and antihistamine medications are a possibility, although unlikely, due to her established disease and chronic medication use. There is no previous case report of such an association in hyperopic shift and no prior head-to-head study looking at specific types of CBD oils and other forms of cannabinoid products. This novel isolated incident between CBD oil and change in VA requires additional, controlled, blinded research for further applicability.
The content published in Cureus is the result of clinical experience and/or research by independent individuals or organizations. Cureus is not responsible for the scientific accuracy or reliability of data or conclusions published herein. All content published within Cureus is intended only for educational, research and reference purposes. Additionally, articles published within Cureus should not be deemed a suitable substitute for the advice of a qualified health care professional. Do not disregard or avoid professional medical advice due to content published within Cureus.
CBD & the Eyes: Research & Can It Help You?
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CBD has become a touted treatment for various issues, including glaucoma. This is based on older medical studies and anecdotal reports that CBD oil, eye drops, and other forms of medical marijuana help to ease anxiety, eye strain, and eye pressure.
One of the first studies on medical marijuana for eye conditions involved glaucoma. This is a group of serious eye disorders associated with damage to the optic nerve, usually due to high fluid pressure in the eye, or intraocular pressure (IOP). This pressure must be lowered to prevent blindness. Further studies of medical marijuana have found that the drug does not actually lower pressure for long enough.
The United States Food and Drug Administration (FDA) has approved CBD for some very limited medical uses, and several states have legalized both medical and recreational use of marijuana, both THC and CBD.
Dispensaries recommend CBD for eye treatment, especially glaucoma. Medical research has found that medical marijuana does not lower eye pressure for more than three or four hours, which is not long enough to prevent damage to the optic nerve. Paradoxically, it may increase the risk of damage due to fluctuations in eye pressure over the course of the day.
In fact, a recent medical study found that THC, not CBD, lowered eye pressure. By itself, CBD raises IOP, and in combination with THC, it can prevent THC from lowering IOP. THC is the intoxicating, recreational chemical in marijuana, which can be addictive and cause problems with thinking or memory.
It is important for you to follow medical advice from your optometrist and ophthalmologist to manage all eye conditions, from dry eyes to glaucoma. Don’t attempt to self-treat any eye issue with CBD.
Table of Contents
Cannabidiol (CBD) & Your Eyes: High Intraocular Pressure Is Dangerous
Glaucoma is a group of related eye conditions involving damage to the retina and optic nerve that leads to vision loss, typically due to high fluid pressure inside the eyes. Symptoms tend to start slowly until enough of the optic nerve is damaged that the person develops tunnel vision or another form of lost vision. Regular eye exams can help to diagnose glaucoma or high ocular pressure, so an optometrist or ophthalmologist can monitor this progression and ensure you receive appropriate treatment if you begin to lose your sight.
Treating glaucoma starts with medicated eye drops that are designed to lower intraocular pressure. If these do not work, there are several approaches to surgery that can lower fluid pressure in the eyes and prevent vision loss.
There are side effects to all these options, so many people with glaucoma, or who are at risk for glaucoma, want to find alternatives. One proposed alternative is CBD oil, or the cannabidiol molecule derived from medical marijuana.
Using Medical Marijuana Like CBD for Your Eyes Does Not Work
As marijuana has become more popular and many states have legalized both medical and recreational uses for this drug, CBD oil is being promoted for a range of uses, including as a glaucoma treatment.
There are very few medical studies on the effectiveness of CBD or medical marijuana, although the United States Food and Drug Administration (FDA) has information on potentially beneficial uses for this approach to treatment. They have approved one CBD-based drug for two types of severe, rare epilepsy. Some forms of medical marijuana have been examined to treat eye conditions, especially glaucoma, but newer research suggests that CBD is not an effective treatment for your eyes.
Medical marijuana has been touted to generally ease physical and emotional pain, including nausea related to cancer treatment, chronic pain, general anxiety disorder, and other conditions. In the 1970s and 1980s, medical marijuana was studied as an eye treatment, particularly for serious conditions like cataracts and glaucoma, which can lead to blindness. The research found that marijuana could lower intraocular pressure for three or four hours at a time, and it was more effective at lowering pressure in the eyes than glaucoma drops.
However, the studies also found that these pressure-lowering effects would wear off after a certain amount of time, while the effects of glaucoma eye drop treatment lasted at least 12 hours. It is vital for eye health that treatment to manage intraocular pressure lasts for a long time and is consistent. When eye pressure rises and lowers several times throughout the day, damage to the optic nerve can get worse.
Medical Studies on CBD & the Eyes Suggests CBD Is a Dangerous Chemical
CBD in particular is receiving a lot of attention from the medical community and medical marijuana proponents. However, studies suggest that the CBD compound may make intraocular pressure higher, while THC (tetrahydrocannabinol), the chemical in marijuana associated with substance abuse and getting high, is responsible for lowering eye pressure.
A study conducted in 2018 found that THC and CBD regulate eye pressure differently. When they are separated from marijuana, they will have radically different effects.
The results of the 2018 study found that a single dose of THC drops lowered IOP by 28 percent for 8 hours in male mice, although humans with glaucoma need 24-hour pressure relief to reduce damage to the optic nerve. The study also found two interesting problems. First, CBD inhibited THC from lowering IOP. Second, the effects of THC on eye pressure were sex-dependent, with male mice receiving noticeably greater benefit from the treatment.
- Accelerated heartbeat, which can trigger anxiety or feel like anxiety.
- Decreased blood pressure overall, which can be harmful to the cardiovascular system.
- Reduced blood flow to several parts of the body, including the optic nerve, which can increase damage.
- Increased risk of lung cancer specifically from smoking or vaping marijuana products.
- Greater risk of addiction with any amount of marijuana treatment containing THC.
- Drowsiness, memory loss, and cognitive issues associated with abusing marijuana.
- Struggles to hold down a job or drive safely if drug-tested.
Most medical research suggests that CBD does not intoxicate you the same way THC does, but taking types of medical marijuana marketed as “high CBD” might mean there are traces of THC included in the substance. THC is addictive because it can change brain chemistry to make you feel relaxed, less anxious, sleepy, or even happy. The drug can also cause negative side effects like changes in mood, spikes in anxiety or paranoia, delusions, and trouble thinking or problem-solving.
Follow Your Eye Doctor’s Treatment Plan for Treating Eye Conditions
Some dispensaries hype CBD for the eyes aside from glaucoma treatment, suggesting that it can ease pain from surgery, reduce dry eye, and even alleviate eye strain. However, there are no medical studies to back up these claims. The changes to eye pressure due to CBD may lead to damage to your vision, even if you do not have glaucoma.
The only currently approved medical approach for glaucoma is regular eye exams to monitor the condition. Follow your eye doctor’s advice to manage this condition if you are diagnosed with it. This will likely mean eye drops first to prevent vision loss. It could also mean laser eye surgery, drainage devices, or other types of surgery to alleviate intraocular pressure and reduce damage to the optic nerve.
Glaucoma. (July 2020). National Eye Institute (NEI).
Cannabidiol (CBD) – What We Know and What We Don’t. (August 2018). Harvard Health Publishing, Harvard Medical School.
Is There a Risk of Blindness With CBD? (2018). United States Food and Drug Administration (FDA).
CBD Oil May Worsen Glaucoma. (February 2019). American Academy of Ophthalmology (AAO).
What Is Marijuana? (December 2019). National Institute on Drug Abuse (NIDA).
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CBD and Glaucoma — Are They a Safe Combination?
Often touted as a magical elixir, CBD is being marketed as a treatment for just about everything, including anxiety, insomnia, pain, and even cancer. According to AARP , baby boomers are fueling its popularity and using it as a treatment for pain, arthritis, and other age-related health problems. But is CBD and glaucoma a safe combination?
The truth is that CBD oil and other products are not a good form of glaucoma treatment. In fact, it may actually increase the pressure in your eye and make your condition worse. THC, the psychoactive chemical in marijuana, may help. However, you need to use it a lot for the same effects as traditional treatment, which has its own risks. Your best choice is medicated eye drops and oral medications in the early stages, and surgery if your condition progresses.
CBD and Glaucoma — A Dangerous Combination
CBD ( cannabidiol ) is a major chemical component in marijuana that has become a popular remedy over the past few years. It can be found in oils, sprays, creams, and even dog treats. Part of its popularity is that it doesn’t get you high, although some CBD products do contain small amounts of its psychoactive cousin, tetrahydrocannabinol (THC).
CBD has many purported benefits such as helping with pain relief, stress, and even cancer-related symptoms. Unfortunately, they don’t extend to the intraocular pressure associated with glaucoma. In fact, a 2018 study from Indiana University found that it can actually increase pressure within the eye .
The study revealed that the use of CBD caused an 18 percent increase in pressure within the eye. These effects lasted for a minimum of four hours, showing that CBD can actually worsen glaucoma rather than effectively treat the eye condition. This is highly problematic since increased pressure inside the eye can eventually lead to irreversible vision loss.
On the other hand, THC provided the opposite and desired effect. Rather than increasing eye pressure, researchers found that it actually lowered it. Male mice experienced around a 30 percent reduction eight hours after being exposed to the chemical. Some male mice had a slightly lower drop to 22 percent lasting four hours.
Female mice didn’t benefit as much from THC. They only experienced a 17 percent decrease after four hours. There was no drop in eye pressure after eight hours. This has led researchers to suspect that females are less affected by THC, although it isn’t clear if this is also the case for its psychoactive effects. The study was originally published in the journal of Investigative Ophthalmology & Visual Science .
The Connection Between Mice & Humans
While performed on lab mice, the results of the study can have an important impact on CBD usage in humans. According to Dr. Alex Straiker, who led the study:
This study raises important questions about the relationship between the primary ingredients in cannabis and their effect on the eye. It also suggests the need to understand more about the potential undesirable side effects of CBD…
The American Academy of Ophthalmology currently doesn’t support the use of THC due to its medical and legal limitations as well as its risks . You would need to smoke eight to 10 times every 24 hours to effectively treat glaucoma. Its side effects wouldn’t make a good long-term treatment plan since they would interfere with everyday tasks and harm your lungs over time . increase your risk of lung cancer.
Click here to learn more about your risk of glaucoma-related vision loss!
Glaucoma Treatment in Knoxville, Tennessee
Baptist Eye Surgeons has been preserving eyesight for the Knoxville and East Tennessee area since 1987. Glaucoma works by damaging the optic nerve over time, resulting in gradual vision loss. This nerve damage is often the result of increased eye pressure, but it can be caused by other factors in certain instances.
Effective treatment for glaucoma starts with a comprehensive eye exam . These dilated exams can help diagnose glaucoma as well as other eye conditions such as cataracts and macular degeneration. Treatment in the early stages involves eye drops and oral medications to help control your eye pressure. Surgery may become necessary if your condition progresses.
Another option is the Xen Gel Stent , a minimally invasive implant. Studies suggest that this surgical option may help reduce your eye pressure as well as your need for medicated eye drops.
Are you concerned about your glaucoma symptoms? Contact us today to schedule your appointment!
Baptist Eye Surgeons is an ophthalmological practice in Knoxville, TN, and Morristown, TN. Give us a call at 865-579-3920 for more information or to schedule an appointment .