Eyeworld

134 | EYEWORLD | APRIL 2019 G UCOMA death by scavenging toxic reactive oxygen species produced by overstimulation of receptors for glutamic acid. 3 "Perhaps the potent antioxidant properties of the cannabinoids may be beneficial in [age-related macular degeneration], offering a possible alternative to established antioxidant supplements," the authors wrote. "Some publications have suggested that cannabinoids can be neuroprotective, so that has some implications for retinal diseases like retinitis pigmentosa. The results are mixed, and I would say contradictory," said Alex Straiker, PhD. A recently published study that received attention in the consumer press focused on both CBD and Δ9-tetrahydrocannabinol (THC, the main psychoactive ingredient in cannabis) and their role in regulating IOP. 4 "Over the last several years, we have determined that three differ- ent cannabinoid receptors—CB1, GPR18, and GPR119—each can lower pressure in mice when activated. Once this was established, it made sense to go back to THC and CBD to see how they act," said Dr. Straiker, one of the study's co-re- searchers. Their study provided topical application of both THC and CBD in mice, and researchers found the CBD actually raised IOP. At the same time, THC lowered IOP through a combination of CB1 and GPR18 receptors. The effect of THC was sex-dependent, with longer effects in male mice. Additionally, CBD canceled out the IOP-lowering effects of THC, probably by block- ing CB1 receptors, Dr. Straiker said. Between research and practice, for now, there is no CBD treatment recommended specifical- ly for the eyes. "It is not an effective treatment for any ophthalmologic issues," Dr. Tishler said. "Further, the high doses needed to see any result in illness are not achievable in eyecare." In her own review of the research, Dr. Clifton sees potential for CBD and certain eye health issues. "It makes sense that taken internally, it would help inflammation or pain syndromes affecting the eye, just like it does any tissue," Dr. Clifton said. She perceived several of the previous studies conducted as biased against cannabis. Research on CBD in the U.S. likely will ex- pand now that it is no longer classified as a Sched- ule 1 drug, Mr. DeRose said (marijuana is still on the Schedule 1 list from the Drug Enforcement Act). One of many questions that could be ex- plored with further research is what happens in subjects who smoke high-CBD varieties of canna- bis, Dr. Straiker said. In practice Ophthalmologists can use their growing knowl- edge of CBD to guide patient queries appropri- ately, particularly in states where marijuana has been legal for a longer length of time. "CBD is a very common topic of ongoing education throughout Colorado," said Antonio DeRose. "This has helped reduce negative stigma and spread positive awareness for several me- dicinal properties, which in turn is leading more people to turn to CBD over certain prescriptions and over-the-counter medications." However, Dr. Tishler said that this can be dangerous if done Mar uana use for glaucoma not effective Although there's a common percep- tion that marijuana can help lower IOP, that is not a formal recommendation from ophthalmologists. "We have known since 1971 that smoking marijuana does lower your eye pressure, which is the main treatment for glaucoma. However, the eye pressure lowering effect is very short acting," Dr. Chan said. For someone to achieve a sustained IOP lowering, they need to con- stantly use the drug, which could lead to systemic changes to the brain, lungs, and cardiovascular system, he explained. Cannabis for glaucoma "is entirely impractical and dangerous," Dr. Tishler said. In a 2014 paper, the American Academy of Ophthalmology said there is no evidence that marijuana provides an increased benefit for or diminished risk of glaucoma compared to the traditional treatments available. 5 References 1. World Health Organization. Cannabidiol: Pre-review report. November 2017. www.who.int/ medicines/access/controlled- substances/5.2_CBD.pdf 2. Bouskila J, et al. Cannabinoid receptors CB1 and CB2 modulate the electroretinographic waves in vervet monkeys. Neural Plast. 2016;2016;1253245. 3. Tomida I, et al. Cannabinoids and glaucoma. Br J Ophthlamol. 2004;88:708–13. 4. Miller S, et al. Δ9-tetrahy- drocannabinol and cannabidiol differentially regulate intraocular pressure. Invest Ophthalmol Vis Sci. 2018;59:5904–5911. 5. AAO Complementary Therapy Task Force, Hoskins Center for Quality Eye Care. Marijuana in the Treatment of Glaucoma CTA – 2014. June 2014. www.aao.org/ complimentary-therapy-assess- ment/marijuana-in-treatment-of- glaucoma-cta--may-2003 Contact information Chan: vp1600@yahoo.com Clifton: marywendtmd@gmail.com Green: beegreeninsarasota@hotmail.com DeRose: antonio@greenhousehealthy.com Morrison: sam@cbdirective.co Straiker: straiker@indiana.edu Tishler: doc@inhaleMD.com continued from page 132

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