Two major cannabinoids found in cannabis, cannabidiol (CBD) and tetrahydrocannabinol (THC), have demonstrated they offer neuroprotective effects that encourage eye health and prevent vision loss. Research has shown that both cannabinoids function as antioxidants and neuroprotective agents, which allow them increase cell survival within the eyes (Chen, et al., 2005) (Hampson, Grimaldi, Axelrod & Wink, 1998) (Nucci, et al., 2008). One study found that both CBD and THC limit the formation of peroxynitrate, which is responsible for retinal neuron death (El-Remessy, et al., 2003). Another concluded that the neuroprotective effects provided by cannabinoids may help slow the vision loss in the case of degenerative disorders like retinitis pigmentosa (Lax, Esquiva, Altavilla & Cuenca, 2014). Most recently, research has shown cannabinoids to make the cells in the retina more sensitive to light, thus improving low-light vision and once again suggesting that cannabis could be beneficial in the treatment regimens of patients with degenerative eye diseases (Miraucourt, et al., 2016) (Russo, et al., 2004).
Research has also shown that the body’s endocannabinoid system plays a role in the regulation of vasoactivity in the eyes. Numerous studies have demonstrated that CBD and THC are effective at decreasing intraocular pressure, making it beneficial in the efforts toward treating glaucoma (Pinar-Sueiro, Rodriguez-Puertas & Vecino, 2011) (Tormida, et al., 2006) (Liu & Dacus, 1987). An animal study showed that CBD inhibited vasoconstriction of the retina (MacIntyre, et al., 2014). The vasorelaxing effects of CBD and THC reduces pressure in the eyes and therefore the risk of damage (Nucci, et al., 2008).
There was a time when people correlated marijuana and the eyes only with dryness, redness and dilated pupils. Time (and some very pinpointed research) has indeed changed this perception for the better. Now there is an overall consensus of the power of cannabis to help with some eye afflictions, especially glaucoma. But what about the BIG ONE that is estimated to affect 6.3 million baby boomers alone by the year 2030? Might cannabinoid therapy be able to help with age-related macular degeneration as well?
There are cannabinoid receptors in the eye area. In a ground-breaking Finnish study on glaucoma conducted in 2002 and published in the journal Pharmacology & Therapeutics, researcher Tomi Järvinena and his team discovered that the eye area has cannabinoid receptors, making this intricately complicated area of the body also a part of the all-encompassing endocannabiniod system (which helps to balance and regulate all other body systems). In the study, smoking cannabis directly was found to lower intraocular pressure in glaucoma patients, but “the discovery of ocular cannabinoid receptors implied an explanation for the induction of hypotension by topical cannabinoid applications.”
Cannabis is an anti-inflammatory. The fact that cannabis is an anti-inflammatory is nothing new. But cannabidiol has also been shown to be an anti-inflammatory specifically for the retina area, especially when that inflammation is associated with endotoxin exposure and diabetes. Believe it or not, there is a direct correlation between all three of these conditions. Diabetes and macular degeneration often go hand in hand (specifically because of low glutathione levels). Exposure to bacterial endotoxins, on the other hand, can often be an initial cause of MD. And all three of these conditions are instigated by the inflammatory response, which, of course, CBD has proven to be able to mitigate quite effectively.
Cannibinoids have been shown to inhibit VEGF growth. The whole point of administering the grueling injection of drugs directly into the eye for MD patients is because, supposedly, these drugs have the ability to stop the progression of vascular endothelial growth factor (VEGF). But cannabis has also been shown to do the same thing, with little to no harsh side effects. A 2004 mouse model study of gliomas (brain tumors) conducted by researchers at Comlutense University in Madrid, Spain found that cannabinoids inhibited VEGF pathways, thus slowing tumor growth in the mice. The same effect was also seen in two glioma patients as well.