What is Glaucoma?
The optic nerve is responsible for carrying signals from the eye to the brain thus resulting in vision. It should be noted that Glaucoma can damage the optic nerve, and if left untreated, long-standing glaucoma can result to blindness. glaucoma causes increase in pressure within the eye or what is known as intra-ocular pressure which results from abnormalities with the amount of fluid in the front portion of the eye, known as “aqueous humor“, which is secreted by a part of the eye known as the ciliary body. Two things can cause pressure in the eye: a decrease in aqueous humor clearance due to a blockage in the outflow space, or an increase in the amount of aqueous humor in the front eye compartment.
The Types of Glaucoma
Two types of glaucoma exist, which each lead to different symptoms:
Primary open-angle glaucoma [most common], with symptoms such as: Gradual loss of peripheral vision, usually in both eyes, a situation in which the primary attention is focused on one point, a loss of peripheral vision leading to an inability to see anything “on the sides”, and Tunnel vision in the advanced stages
Acute angle-closure glaucoma with symptoms such as: Eye pain, Nausea and vomiting (accompanying the severe eye pain), sudden onset of visual disturbance, often in low light, Blurred vision, Halos around lights and Reddening of the eye
Since many people show no signs of glaucoma until damage has already resulted, it is important to regularly attend appointments with an eye care professional in order to be properly screened.
Can Cannabinoid Therapies Help?
According to a 1979 study published in International Journal of Pharmacology and Biopharmacology , a group of 16 participants with open-angle glaucoma were studied , along with high blood pressure (8 participants) or no high blood pressure (8 participants). The study revealed that when participants inhaled whole-plant marijuana with 2.8% delta-9-tetrahydrocannabinol (THC), the rates of their heats first increased and then their blood pressures and intra-ocular pressures decreased . it should be noted that in order to compensate for decreased blood and intra-ocular pressures caused by THC, the heart starts to pump blood faster in order to maintain blood flow to vital area. The found that the effects were greater and lasted longer in participants with high blood pressure than in those without high blood pressure and even continued for approximately 3-4 hours.
Another research was carried out by the same researchers, assisted by other colleagues in 1980 who together published an article in Ophthalmology which reviwered the results of their 1979 research and suggested that the lowering of blood pressure that led to decreased intra-ocular pressure occurred within 60 to 90 minutes of inhalation. They also reported that since the inhalation of marijuana was associated with side effects of increased heart rate, and psychoactivity or changes in perception, thought, feelings, etc. which is frequently associated with marijuana use , and excessively decreased blood pressure which can trigger feelings such as being lightheaded, as such the ability to recommend inhaled marijuana for patients may be limited.
They also added that the decrease in blood pressure caused by whole- marijuana plant use/THC may lead to a harmful reduction in the flow of blood to an already potentially damaged optic nerve which could further damage the nerve and the fact that the development of cannabinoid therapies are applied directly to the eye, rather than administered systemically to the entire body, as the case with inhalation and ingestion), testing other cannabinoids other than THC may be more appropriate
Another study was conducted by the same researchers 1981 again assisted by additional colleagues, in which 0.1% THC in light mineral oil was administered directly to the eyes (i.e. topically) of human participants with high blood pressure, and results showed a decreased systolic blood pressure (pressure in vessels felt immediately when the heart contracts/pumps) which they suggested may lead to decreased intra-ocular pressure. In guest editorial published in Journal of the National Medical Association in 1982 one of authors noted that in both animal and human studies, the maximum intensity of effect on intra-ocular pressure for topical administration of THC occurs at approximately 6 hours after administration and lasts for 8-12 hours.
Potential Control of Other Symptoms of Glaucoma
The symptoms of glaucoma that may be eased by using marijuana include pain, nausea, and vomiting, and a symptom of glaucoma which may be worsened by using marijuana is eye reddening.
It should however be noted that not all patients with glaucoma will experience decreases in pain, nausea, or vomiting after using marijuana, and that the recommended first-line treatment are standard therapies recommended by a healthcare professional.
Marijuana use may temporarily relieve intra-ocular pressure, but it does not permanently cure glaucoma. Although the use of marijuana has been proven to decrease IOP and has a favorable safety profile in general, its use is limited by: the fact that it only works for a few hours before another administration is needed, which is important because psychoactive of marijuana effects may decrease the ability to perform certain duties necessary in daily life, such as driving, and the use of marijuana is associated with certain side effects that impact the heart and must be carefully considered or avoided in patients with heart issues.