What do CBD, cannabis, and marijuana have do with with optometric care? Find out. Age-Related Macular Degeneration affects 11 million people in the US. Medical marijuana has been shown to potentially help patients manage symptoms of AMD.
Cannabis and CBD oil: a new “old” friend in optometry
Optometric training requires learning about bones, muscles, neurology, and the vascular and other systems. But have you heard of the endocannabinoid system (ECS)?
If the answer is no, that’s not surprising.
Although the ECS is critical for human survival, 1,2 cannabinoid receptors weren’t identified until 1964, 1-4 when investigators were trying to locate where marijuana tetrahydrocannabinol (THC) interacted with the brain. It wasn’t until 1988 that the ECS was identified, and 1992 when it was officially acknowledged. 2-4
Humans operate on the parasympathetic and sympathetic system. The parasympathetic system operates under “normal” conditions.
When the body perceives it is under attack, neurochemicals trigger the sympathetic system, activating the “fight or flight” response. 5,6
The ECS, simply put, disengages the sympathetic system. It is responsible for bringing the body back into balance (homeostasis). 2,7 If it doesn’t, the body is faced with unresolved “danger” from the chemicals and processes that are designed to protect it. These chemicals cause inflammation and begin attacking and damaging the body, 7,8,9 which is then labeled as “such and such” disease. Our rampant, epidemic health problems are self-inflicted, 5,7,10 brought on by our diet, lifestyle, and technology. 7,10,11
The ECS (Figure 1) is made up of 2 main receptor sites, CB1 and CB2. 2,4,7,10
CB1 sites are primarily in the brain, heart, and lungs, and modulate the immune response. CB2 receptors are primarily located in the lymph system, detoxification organs, and peripheral systems to break down and clear out the toxic immune system chemicals and debris. 1,3,7,14,24
The body produces its own chemical—anandamide, known as the bliss chemical—to regulate our systems via the ECS. 7,13,14 Unfortunately, in today’s high-stress environment, it can’t create enough to keep up with the demand. 10,14
Eating dark chocolate, exercising, or being “in the zone” are other ways to feed the CB1 and CB2 receptors. 7,14 Cannabidiol (CBD) was removed from livestock feed when it was made schedule 1 in 1941, so it has not been in the food chain for 80 years. CBD is nature’s external equivalent to supplementing the body’s anandamide shortage. 17,18,24
Technically, cannabis is not marijuana; nor is CBD. Cannabis is the botanical name for the common hemp plant, which has been cultivated for industrial purposes for more than 20,000 years. 15,18,24
The medicinal properties of hemp have been utilized for over 10,000 years. 15 The 2 main classes of cannabis are sativa, which is generally stimulating, and indica, which is generally calming. 16,18
Marijuana is a small subset of hemp that has been bred to produce more “high.” Hemp has over 400 different chemicals, with 100 compounds known as cannabinoids, each creating various effects. 16,18
CBD is one of the most prevalent cannabinoids in the hemp plant; it has the most profound, diverse, and beneficial impact. 16,18 The main takeaway is that cannabis is really just the hemp plant, and CBD is not marijuana.
THC and CBD originate from the same compound and have nearly identical chemical structures (Figure 2). 16,22 Depending on the genetic strain, the hemp will have higher or lower THC and CBD levels. When the flower is beginning to bloom, however, growers must test the plants daily because the CBD in the plant will start to become THC. 16,22
At that point, the growers only have 48 hours to harvest their crop. The legal amount for THC to not be considered marijuana is 0.3%. 19,22
The CBD industry wants as high an amount of CBD as possible with the least THC possible. CBD’s profound effects on all bodily functions are not forced—unlike those of pharmaceutical agents—and nor does the chemical have their toxicities or unintended adverse effects (Figure 3). 20,21,24
As of February 2022, 37 states in the United States have legalized marijuana for medical use and 18 have legalized it for recreational purposes .20 The medical and recreational marijuana market is projected to be $30 billion in 2022. 21
Although marijuana still has legal hurdles to overcome, the CBD market is legal in all 50 states. 22 CBD is also available OTC and thus is free from FDA regulations and red tape. 22 The CBD market is projected to be $2 billion in 2022. 23
This projection will result in both good and bad consequences. Because cannabis has been outlawed as a Schedule 1 drug for 80 years, little controlled research has been undertaken and no distinction made between the effects of THC and those of CBD.
Medical benefits, risks
Much of marijuana use is for the high it produces, but there are some documented medical benefits. These include the relief of pain and nausea related to cancer treatments, aiding of sleep issues, reduction of posttraumatic stress disorder symptoms, easing of symptoms in those withdrawing from opioid addiction, and a calming of symptoms of various neurological conditions. 4,24
Unfortunately, according to more recent findings, marijuana does interfere with cognitive ability, 24,29 damages memory function, and destroys brain tissue. It also causes heart attacks—even in younger people with no underlying conditions—may have negative effects on genetics and pregnancy, and, if ingested by vaping or smoking, increases cancer risks. 24 Thus, marijuana is far from risk free.
Of more direct concern to optometrists are the negative effects of marijuana on the visual system. Both photopic and scotopic vision are impaired due to decreased macular and peripheral sensitivity. 24-35
Neurologically, vision processing is compromised, creating selective scotomas and interfering with one’s ability to navigate in the environment. 24,26-28,30,32-35
The eye is both a specialized neurologic receptor and a person’s primary connection to the physical world. It is important for optometrists to be aware of CBD, as eyes are packed with both CB1 and CB2 receptors.
Consider the major 5 medical conditions optometrists often encounter with when working with patients:
1. Cataracts 37
2. Glaucoma 38,39
3. Macular degeneration 41-43
4. Allergies 46
5. Meibomian gland disease 47
Although each is a separate condition, all have inflammation as the root cause due to the eye being threatened by the environment. 35,40 Many treatments are based on treating the symptoms or slowing the progression of damage by interfering with the ocular response process.
CBD works with the body’s natural system to decrease the inflammation process and restore homeostasis, avoiding the long-term results that define disease.
Peer-reviewed, evidence-based science is limited. However, I have heard anecdotally that some patients have experienced better vision with OTC supplementation of CBD and ocular nutraceuticals, backed by macular pigment ocular density (MPOD), optical coherence tomography (OCT), retinal photographs, and acuity. 43,44
We have accepted that ocular “aging” conditions are normal, inevitable, and unstoppable. 45,57 Perhaps traditional medical treatments would be less necessary if we worked with the natural body system designed to minimize those issues.
Beyond ocular conditions, optometrists must step back and look at the larger medical issues facing humanity.
Obesity, diabetes, blood pressure, heart disease, cancer, Alzheimer disease/dementia, autoimmune conditions (lupus), rheumatoid arthritis, fibromyalgia, multiple sclerosis, neurologic disorders, depression, anxiety, panic attacks, migraines, attention-deficit/hyperactivity disorder, and concussions are all inflammation-related processes caused by an increased assault on our physical system.
This has overloaded the natural mechanism eyecare professionals were designed with to maintain health. Optometrists need to learn about ECS and CBD to augment their toolbox for taking care of patients’ well-being. 6,9,36,48,51,55,56,59-63
Cannabis and CBD for Age-Related Macular Degeneration (AMD)
There is no known cure for Age-related Macular Degeneration (AMD), a condition caused when a tiny part of the retina called the macula deteriorates. Rarely, AMD could lead to permanent vision loss for individuals past the age of 60.
Currently, the National Eye Institute reports that 11 million Americans suffer from this age-related condition caused by the weakening of the macula, although it is likely under reported (10). Made up of photoreceptor cells, the macula detects light and images and signals the brain to interpret what is in the central vision (11). Though there are many types of macular disease, AMD is the most common. When AMD sets in, the macula weakens, causing visual impairments including sharp details becoming blurry, difficulty reading, recognizing faces, and differentiating colors.
Unlike other macular diseases, AMD is directly related to aging, primarily affecting the elderly. Bright Focus reports the global cost of the condition is $343 billion, with up to $98 million in collective healthcare costs for the U.S, Canada, and Cuba (1). According to Johns Hopkins University, age-related macular degeneration is the leading cause of vision loss in people 50 and older, and although it can cause a severe loss of central vision it rarely causes people to go blind (5).
How Cannabis Can Help Relieve the Symptoms of Age-Related Macular Degeneration (AMD)
As an anti-inflammatory agent, THC could reportedly assist in temporarily lowering intraocular pressure and free radicals that lead to vision loss specifically for those living with glaucoma. A study published in Pharmacology & Therapeutics suggests that THC helps lower intraocular pressure, potentially preventing vision loss (6). Meanwhile CBD has a THC-countering effect in the eyes that could block its lowering of IOP (intraocular pressure) (8). Some patients with glaucoma who smoked medical cannabis reported clearer vision. These effects are generally short-term and are not yet confirmed by large studies.
However, United Patients Group reports CBD benefits that may assist with clearer vision (2). For example, it stunts the vascular endothelial growth factor (VEGF). A cancer research study on mice suggested that CBD, “lowered the expression of various VEGF pathway-related genes.” Along with the ability to inhibit VEGF, cannabinoids may theoretically alleviate macular disease symptoms since they inhibit angiogenesis, are neuro-protective and reduce ocular pressure (3). Such effects require direct eye research to confirm, as they can only be extrapolated at this time.
Medical Cannabis and Inflammation
Medical cannabis is a powerful anti-inflammatory drug. Cannabinoids play an important role in the regulation of the immune system through activating cannabinoid receptors in the Endocannabinoid system (ECS).
When your body activates your immune system, it sends out inflammatory cells and signals. These cells attack bacteria and often damage healthy tissue as well. Inflammation is a feature of some degenerative eye diseases such as glaucoma and AMD.
Inflammation is one of the most common conditions targeted with medical cannabis. As stated above, cannabinoids are known anti-inflammatory and antioxidant agents (9). Cannabidiol may be an effective treatment for inflammation in glaucoma patients and individuals with AMD although further research in this area in order to make a recommendation.
Medical Cannabis as a Neuroprotectant: A Patient’s Perspective
A patient in Taos, New Mexico who suffered from AMD found amazing results with CBD after taking it sublingually under her tongue at the suggestion of an herbalist, according to the United Patients Group. However, before finding CBD, the patient had several injection treatments to inhibit VEGF, which are painful and invasive. While the United Patients group reports, “no studies have been done on cannabinoid therapy and AMD directly,” there may be a correlation between taking CBD and improvement in symptoms according to patient reports like this one (2).
Until further research takes place, the use of medical cannabis in the treatment of AMD will continue to be studied along with many other conditions for which patients are successfully using cannabinoids.
Research on AMD and Medical Marijuana
To date, there is no direct evidence that cannabis can help with AMD. Cannabis smoke creates tar that contains some of the similar carcinogens of tobacco smoke, and so any kind of smoking should be avoided to prevent the development of AMD since smoking increases your chances of developing it later in life. It may be possible that forms of cannabis ingestion other than smoking could be beneficial for other aspects of treating symptoms that present with AMD but at this time there is currently no research to support using cannabis for AMD.
Types of Age-Related Macular Degeneration
Understanding the different kinds of AMD is important to have a grasp of the disease on the whole. There are two forms of AMD: dry and wet. Let’s explore the two types of AMD and how they are characterized.
Wet age-related macular degeneration is also called advanced neovascular AMD. It is a less common type of late AMD that usually causes faster vision loss. It’s important to note that any stage of dry AMD can turn into wet AMD—but wet AMD is always a late stage.
It occurs when abnormal, leaky blood vessels grow in the back of the eye and damage the macula. As mentioned before it is the less common type of AMD and only accounts for about 10 percent of cases. Wet AMD accounts for roughly 10% of AMD cases, but 90% of the time leads to legal blindness (1).
Unlike dry AMD, wet AMD can be treated effectively with medication. Treatments can also include visual therapy and vision aids. With regard to pharmaceutical treatments, “ Wet AMD is usually treated using the following medications, which belong to a group of drugs known as anti-vascular endothelial growth factor (anti-VEGF) drugs Ranibizumab (trade name: Lucentis) and Aflibercept (Eylea) (4).”
Side effects of these treatments may include temporary eye pain, raised pressure inside of the eye, and seeing spots or dots that follow the eye’s movements.
Additionally, it should be noted that serious side effects of this treatment are “inflammation of the inside of the eye (endophthalmitis) or the middle layer of the eye (uveitis), cataracts or retinal damage. In total, these types of side effects occur in less than 1 out of 100 people (4).”
Most people with AMD have dry AMD, which is also referred to as atrophic AMD. This is when the macula gets thinner with age. The symptoms of dry AMD depend on the stage. Dry AMD happens in 3 stages: early, intermediate, and late.
It usually progresses slowly over several years, and symptoms tend to worsen over time. While early-stage dry AMD and some cases of intermediate dry AMD typically do not cause symptoms, some patients with intermediate dry AMD and patients with late AMD will often notice symptoms including blurriness and trouble seeing in low lighting. Over time these symptoms progress to colors appearing less bright and the blurry area expanding. Straight lines appearing wavy is a warning sign for late AMD, and patients should seek care from their eye doctor immediately.
Annual dilated eye exams can help catch the early stages of AMD and other optical diseases, which adds to the importance of routine eye exams. Individuals with preexisting conditions like diabetes, hypertension, and hyperlipidemia may need more regular eye exams. Persons with known family history of AMD or vision problems should consult their doctor and optometrist for evaluation and follow up.
There is currently no treatment for late dry AMD, but if unfortunately caught in a late stage you can find ways to make the most of your remaining vision and relieve symptoms. Prevention and early detection are always best practices.
Risk Factors of Age-Related Macular Degeneration
According to Mayo Clinic, risk factors of AMD include:
- Age – People over 60 are at higher risk
- Family history and genetics – Several genes are linked to this disorder that can be inherited
- Race – Caucasian people have more odds of developing AMD
- Smoking – First and second-hand smoke increases odds of developing AMD
- Obesity – May accelerate the development of intermediate stage AMD to more severe late stage
- Cardiovascular disease – Conditions that affect the heart and blood vessels like diabetes and high blood pressure may increase the risk of AMD (7).
Lowering Your Risk for AMD
Research shows that you may be able to lower your risk of AMD (or slow vision loss from AMD) by making these healthy choices:
- Avoid smoking
- Regular physical activity
- Maintain healthy blood pressure and cholesterol levels
- Eat healthy foods, including foods high in nutrients such as leafy green vegetables and fish (10)
Note: The content on this page is for informational purposes only and is not intended to be professional medical advice. Do not attempt to self-diagnose or prescribe treatment based on the information provided. Always consult a physician before making any decision on the treatment of a medical condition.