The Amazing Use of Cannabis For Glaucoma Treatment
Throughout 1971 the first research by Hepler and Frank showed that inhalation of cannabis was related to a reduction in IOP, Thus, research for Glaucoma treatment has since found that the relationship between intake of cannabis and glaucoma optic neuropathy has been more complex.
Significant differences in IOP-reduction effects of cannabis have been identified based on the chemical composition and the specific crop line of clinical and basic science studies. Cairo’s and other collaborators have found that tetrahydrocannabinol (THC), one of the major components of cannabis, decreases the IOP by connecting to the CB1 receptor in the ciliary and trabecular mesh-cell cells. 2 However, cannabidiol (CBD) is another important component of cannabis, having the opposite effect on IOPs and potentially harmful consequences for persons with glaucoma.
In six patients suffering from ocular hypertension, or mild primary open-angle glaucoma, Tomida and her colleagues carried out a random, double-masked, placebo-controlled crossover study. 3 Patients were randomly assigned sub-legal THC, sublingual CBD (20 mg), higher-dose sublingual (40 mg) CBD, or a placebo after the usual topical IOP-lowering schemes have been washed. In comparison with placebo, patients treated with THC had modest decreases in IOP two hours after treatment, whereas those treated with the higher dose of CBD saw a modest improvement in IOP.
Many such clinical findings corroborate Miller’s basic science research and the use of topical THC and CBD for live mice. 4 Researchers have also tested CB1 knockout mice to clarify the effects of these agents. Topical THC is below IOP for 8 hours, while topical CBD has produced substantial increases in IOP. Interestingly, it was not observed in CB1 knockout mice, which indicated that CBD could have antagonistic action against THC in this receptor. THC and CBD were used simultaneously, probably not because every agent’s effect was canceled. The effect of the mouse IOP was not noticeable.
Glaucoma treatment Implications
In most of the United States, cannabis is approved for medicinal use. This substance has also been approved for recreation by a growing number of countries. Apart from glaucoma, the treatment of conditions such as cancer, irritable bowel syndrome, and various pain conditions is also approved for medical cannabis. It must be noted that states with approved medical cannabis do not differ between strains of the cannabis flowers for these indications.
Therefore the levels of THC and CBD vary between products, but studies have shown that not every strain of cannabis has the same effects. 2-4: 2-4 As previously described, higher THCs can be expected to decrease IOP, while higher CBD strains can increase IOPs. Therefore, it is important to warn eye care professionals that patients interested in using medical cannabis to treat their glaucoma can cause a damaging effect on their disease process by using products that have a high CBD content.
Although many medical cannabis studies have shown a limited length of activity and regulatory mechanisms, including euphoria and hypotension, for treating glaucoma. As a result of these problems, several esteemed healthcare companies have held that the potential advantages outweigh the risks associated with cannabis intake. Also, IOP-reducing treatments with medical, laser, and surgeon techniques currently available are more effective in their present state than cannabis-derived therapies.
However, research such as that by Tomida et al. suggests that the mixed results of earlier studies on the effect of cannabis on IOP could be linked to the consumption of different strains of THC and CBD in different ratios. Therefore, the strain and composition of the THC/CBD should be better evaluated for further studies investigating the reduction of cannabis and IOP.
Consideration for medical benefits and uses
The medicinal value of cannabis should be balanced against the potential of unfavorable adverse effects with eye consequences in glaucoma therapy. An American Glaucoma Society fact sheet written by Henry Jampel, MD, MHS, points to these detrimental reactions, including but not limited to alterations in moods resulting in reduced mental fitness, respiratory damage, and systemic hypotension. One important consideration is that a decrease in the pressure of the eye infusion and progressive glaucoma could result from systemical hypotension. Furthermore, marijuana inhalation is related to short-term action in reducing IOP and rebound ocular hypertension potential.
Cannabinoids may exert cytotoxic activity that can ultimately alter the course of glaucoma in addition to the potential for IOP lowering. Studies showing that concept could reduce systemic effects and allow repeat dosing by topical formulations of cannabis. The obstacle is that cannabinoids are lipophilic and poorly absorbed by the eye and cause eye irritation. Kabiri and fellow workers have described a new method of loading cannabinoid mime molecules in a hydrogel loaded with nanoparticles.
The hydrogel is a hyaluronic acid–methylcellulose composite and is supposed to be dosed in the evening. This method achieves a high degree of corneal penetration in the study by Kabiri et al. 7 A recent cannabinoid cannabinol study has shown that this agent may be antiapoptotic and neuroprotective in an in vitro model for cytotoxic stress-related ganglion cells.
It has been almost 50 years since Hepler and Frank first showed that they have associated cannabis with glaucoma therapy and that the understanding of cannabis effects on glaucoma has been slow to progress for researchers and clinicians. As the availability and interest in medical cannabis grow, it is reasonable to think that research will be accelerated in this field in the next few years.