Glaucoma is one of the leading causes of blindness in the US. According to the Global Burden of Diseases study 2010, nearly 2.1 million people were blind while 4.2 million were visually impaired due to Glaucoma. These numbers were projected to increase widely over the next couple of decades.
This eye condition occurs due to the damage to the optic nerve. The most common reason for glaucoma is fluid build-up in the front part of the eye. This fluid build-up increases pressure on the eye, damaging the optic nerve, and results in permanent damage to the vision.
Glaucoma can occur at any age but is common in adults over the age of 40. This condition can lead to permanent vision loss.
What we know about CBD and Glaucoma?
The role of CBD in reducing or treating Glaucoma is unclear. With conflicting research and studies showing different results, further clinical trials will help establish the role of CBD for glaucoma.
Let us first understand glaucoma and its effects on the patients suffering from the condition.
As mentioned earlier, glaucoma occurs due to damaged optic nerves. The optic nerve is the most essential organ responsible for vision. It works by sending signals to the brain in the form of images.
When the pressure in your eye, also known as the intraocular pressure, increases because of fluid build-up, it starts affecting the optic nerve.
This nerve damage results in vision problems as it can no longer send signals to the brain. When this damage worsens, you will experience permanent blindness.
Glaucoma doesn’t show any signs in the early stages. This makes it difficult to detect and treat at the correct time. Unless you visit an ophthalmologist for regular check-ups, you won’t be able to identify this condition.
By the time the symptoms start showing, deterioration sets in. Ultimately, this condition results in permanent blindness.
Medications are available to lower intraocular pressure. But they can cause intolerable side effects such as burning, blurred vision, and tearing. Long term use can also reduce the efficacy of these drugs.
A study by the British Journal of Ophthalmology states that “..different cannabinoids, including cannabidiol, cannabigerol, endogenous cannabinoids, and some synthetic cannabinoids, can reduce the IOP when administered systemically and topically.” This feature along with cannabinoids’ neuroprotective properties can make CBD a good agent to treat Glaucoma.
The hemp plant contains over a hundred different cannabinoids, flavonoids, and terpenes. These compounds are responsible for most of the therapeutic properties of the hemp plant. Among the various cannabinoids, THC and CBD are of chief interest.
In 1971, a study on a small number of subjects conducted by Helper and Frank showed that smoking marijuana lowered the Intraocular Pressure or IOP by about 25 to 30%. The effect lasted for about 3 to 4 hours. The subjects reported side effects such as lesser tear production, changes in pupil size, tachycardia, etc.
Long term use of smoking marijuana has the possibility of developing tolerance. The reduction of the intraocular pressure seemed to be inversely related to the duration of marijuana smoking.
On the contrary, another study conducted by Dawson et al showed that marijuana users of 10 years or more and non-users showed a similar reduction in IOP after marijuana treatment.
Studies like the one published in the Journal of Ocular Pharmacology and Therapeutics show that cannabinoids like CBD and CBN were able to reduce the IOP.
Smoking cannabis can be unhealthy due to its various side effects. Therefore scientists have started looking for other safer and effective methods for administering CBD to reducing IOP, thus reducing the effects of Glaucoma.
Oral Administration of CBD for IOP in Glaucoma:
A study published in the Journal of Glaucoma studied the effects of oral administration of low doses of CBD and THC on intraocular pressure.
The findings were as follows:
- A single dosage of 5mg of THC could reduce the pressure temporarily. Most of the patients showed good levels of tolerance to the dosage.
- While the sublingual administration of 20mg CBD didn’t reduce IOP, a 40 mg dosage was able to slightly reduce the IOP.
Topical Administration of CBD for IOP in Glaucoma:
Topical application is one of the safer methods of administering CBD to maximize the results and minimize the side effects. Scientists applied the same principle to observe the effectiveness of CBD in reducing IOP in the form of eye drops.
One problem they encountered while conducting the experiments was that the cannabinoid extracts were lipophilic making them difficult to dissolve in water. As a result, administering them in the form of eye drops proved to be a challenge.
Since the surface of the eye is constantly moist due to tears, water solubility is extremely important for the eye drops to be effective.
With the administration of any eye drops, much of the solution goes waste due to lacrimal drainage. As a result, only about 5% of the dose reaches the intraocular tissue.
These factors were a challenge for scientists trying to test the topical administration of cannabinoids for glaucoma.
A study by Keith Green and Walter.M.Jay published in JAMA Ophthalmology employed 28 male volunteers who were administered THC that used mineral oil as the solvent. Most of these volunteers experienced side effects such as eye irritation, burning sensation, and swelling in the eyelids.
According to the studies published in the Journal of Current Eye Research and the Life Sciences journal, cyclodextrin, methylcellulose, and polyvinyl alcohol improve the aqua-solubility of cannabinoids, making them the best carriers for oral administration of CBD.
This study provides value for scientists and researchers working on the IOP-reducing properties of CBD through topical administration.
Neuroprotective properties of CBD for Glaucoma:
In Glaucoma, reducing the intraocular pressure by itself may not be enough to prevent vision loss.
A study on the neuroprotective effect of THC and CBD published in The American Journal of Pathology details the role of glutamate-induced neurotoxicity in glaucoma.
Glutamate is an important neurotransmitter. It is present in high concentrations in the retinal cells or the retinal ganglion cells. Certain conditions can cause glutamate to release in higher amounts. This excess release leads to the death of the retinal ganglion cells which in turn contributes to glaucoma.
The study explains the role of glutamate in causing the death of the retinal neurons due to the excess formation of peroxynitrite. THC and CBD may reduce the formation of peroxynitrite, thereby protecting the retinal neurons and the ganglion cells.
The neuroprotective properties of THC and CBD play a significant role in reducing the excess formation of glutamate. This happens due to the activation of the CB1 receptor which is a part of the body’s endocannabinoid system or ECS.
The ECS including the endocannabinoids and its receptors is present in the ocular tissues and the retina. The endocannabinoids are present throughout the eyes, the only exception being the lens.
The ECS system is responsible for maintaining various systems of the human body. The endocannabinoids and receptors together form a network with each of them being responsible for one or more systems and functions.
Through this network, the ECS system is responsible for maintaining coordination between various processes and systems for smooth body metabolism. In other words, the ECS system maintains homeostasis.
A disturbance in this homeostasis, usually due to an injury or inflammation, can disturb the endocannabinoid system and its functioning.
In such situations, other receptors and pathways may initiate the process of protecting the nerve cells from death.
By therapeutically modifying the ECS system, it may be possible to reduce nerve death, thereby improving the symptoms that occur due to glaucoma.
The neuroprotective properties of CBD in combination with its anti-inflammatory and antioxidant properties can make it an ideal candidate to curb the neuron damage and neuron death in glaucoma.
The THC cannabinoid can activate the CB1 and CB2 within the ECS system to trigger the neuroprotective properties, and thus may provide relief from glaucoma symptoms that occur due to cell death, and also restore vision to some extent.
Since THC is associated with certain unwanted symptoms, and due to its psychoactive effects, the therapeutic properties of CBD as a neuroprotective agent are under focus.
The neuroprotective properties of CBD may be due to its ability to activate certain signaling pathways. Besides, CBD also attached itself to the CB2 receptors which then triggers the neuroprotective properties, preventing nerve damage and death.
Both THC and CBD have shown protective action against retinal injury, strengthening their position as possible therapeutic candidates for Glaucoma.
Along with its neuroprotective properties, CBD also inhibits the degradation of certain cannabinoids that act as neuroprotectants. THC may play an additional role in activating certain neuroprotective pathways.
Antioxidant properties of CBD
We already know that elevated glutamate levels act as one of the risk factors for Glaucoma by initiating the death of the ganglion cells and nerves. In vivo and in vitro studies have shown that such nerve death can be reduced with the presence of antioxidants.
Antioxidants work by reducing the production of peroxynitrite, the factor that is chiefly responsible for triggering the cell and nerve death.
CBD and THC have both shown potent antioxidant properties by protecting nerves from glutamate-induced death and oxidative stress as well.
Despite the growing evidence of CBD as an ideal therapeutic candidate for treating glaucoma, certain factors still put it in a jeopardy.
In most cases, CBD may not be able to act alone to deliver therapeutic properties such as lowering the intraocular pressure, protecting the nerves, and rendering its antioxidant properties.
There is still conflicting research if CBD will be able to act alone or will need THC as its partner to be able to render all the properties.
Since it attaches itself to the CB1 receptors, THC displays certain psychoactive properties which may cause unwanted side effects with regular use.
Another study shows that CBD in higher amounts, when paired with THC can counter the unwanted THC’s side effects while retaining the therapeutic properties of both the compounds.
While this factor may pose some hope for THC and CBD as possible glaucoma therapy agents, further research will be necessary to arrive at a concrete conclusion.
CBD for treating the symptoms of Glaucoma:
Glaucoma is a serious eye condition marked by nerve damage and subsequent vision loss. The condition starts with fluid build up behind the eye.
Under normal conditions, the eye has the presence of fluid called aqueous humor. This fluid usually drains out through a mesh-like channel. In some cases, this mesh-like channel gets blocked and with no outlet, the fluid starts building up in the eye.
This fluid build-up increases pressure on the optic nerve which is responsible for sending image signals to the brain. With the resultant pressure, the optic nerve starts getting damaged and you can sense a lessening vision.
A completely damaged optic nerve results in total vision loss. Usually, once the reduction in vision starts, deterioration is quite quick, giving you little or no time to consult an ophthalmologist for treatment.
While this condition is most commonly seen in adults over 40, it can occur in people of any age group, including infants and children. This condition can be inherited, meaning it runs in families.
Conditions such as diabetes, high blood pressure, heart disease, etc can result in glaucoma. Also, certain medications increase the risk factors for getting glaucoma.
Sometimes an injury in one or both the eyes can cause glaucoma in the long run. If you have thinner corneas or suffer from eye pressure, you may be at risk of getting glaucoma at some point.
Symptoms of Glaucoma:
To understand the symptoms of glaucoma, we must first understand the types of this condition.
Glaucoma is categorized into four types for a general understanding, though there may be even more types from a medical or therapeutic point of view.
This is the most commonly occurring form of glaucoma and is also known as wide-angle glaucoma. The drainage angle remains open, but the mesh is partially blocked, resulting in gradual pressure build-up. This glaucoma takes a long time to completely block your vision.
This glaucoma type doesn’t cause any pain to the eye. You will not notice any vision changes in the initial stages. Regular eye check-ups are crucial to detect and treat the condition early
- Blind spots and patches in the central and peripheral visions in one or both the eyes.
- Tunnel vision occurs in advanced stages.
This condition is also known as chronic angle-closure or narrow-angle glaucoma. As the name suggests, the drain angle or the space between the iris and the cornea becomes too narrow. This blocks the fluid from draining out. This results in a sudden build-up in your eye.
Angle-closure glaucoma is sometimes linked to far-sightedness or cataracts. It is marked by the clouding of the lens in the eye.
- The appearance of halos around lights
- Severe headache
- Nausea and vomitings
- Blurred vision.
- Eye pain
- Eye redness
- Blurred vision
Some doctors consider this as a form of open-angle glaucoma. With this condition, the eye pressure remains normal to average, but can still cause damage to the optic nerve.
While the exact causes of this kind of Glaucoma are not known, symptoms include the appearance of blind spots in the vision.
Pigments from the iris block the drain channels resulting in a pressure build-up on the optic nerve.
- Difficulty with side vision
- Rarely, the appearance of haloes or blurry vision.
Some of the more significant causes of glaucoma such as pressure build-up and nerve damage may be treated with the pressure reducing and the neuroprotective and the antioxidant properties of CBD. These symptoms can include blurry vision, the appearance of halos around light, etc.
Let us look at the role of CBD in treating the common symptoms of CBD which include:
- Eye pain.
CBD for Eye Pain and Headaches:
CBD has analgesic and anti-inflammatory properties. A study published in Cannabis and Cannabinoid research also states CBD and THC may reduce corneal pain.
According to the same study, THC may reduce pain and inflammation by binding with the CB1 and CB2 receptors. CBD may activate the non-cannabinoid receptors for a reduction in pain and inflammation.
With these properties, CBD and THC may provide relief from symptoms such as redness in the eye, eye pain, and headaches.
CBD for Nausea and Vomitings:
CBD has antiemetic properties. It can suppress nausea and vomitings within a limited dose range according to a study “Regulation of Nausea and Vomitings by Cannabinoids”
With its pressure reducing, neuroprotective, analgesic, anti-inflammatory, and antiemetic properties, CBD may provide relief and to a certain extent treat glaucoma.
Consulting an experienced ophthalmologist who has expertise in CBD is crucial before starting CBD for glaucoma, as you must consider multiple aspects before starting this alternative line of medications.
The presence of THC may prove a hurdle in certain cases. The presence of this cannabinoid along with CBD can prove more effective to treat Glaucoma, than CBD acting alone.
Also, the effectiveness of THC/CBD as compared to the dosages still needs to be established. Further studies are needed to establish the safety of THC to treat Glaucoma when compared with the risk factors.
To sum up, CBD may be effective to treat Glaucoma and its various symptoms. Further investigations and clinical trials will help strengthen the theory.