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Affecting more than 10 million Americans, macular degeneration is an incurable eye disease caused by the deterioration of the retina. Studies have found that cannabis has neuroprotective properties, suggesting it could be beneficial for maintaining retinal health.
Overview of Macular Degeneration
The leading cause of vision loss, macular degeneration is caused by the deterioration of the central portion of the retina. That central portion, called the macula, is responsible for recording the images seen and sending them via the optic nerve from the eye to the brain for interpretation. Its deterioration, which is gradual, leads to images not being received correctly.
Macular degeneration, also referred to as age-related macular degeneration (AMD), occurs in three stages. Early AMD is when small yellow deposits, called drusen, develop beneath the retina. During this early stage, there is no vision loss and therefore the ability to catch AMD early on only happens during routine eye exams. At intermediate AMD, the drusen are larger and there may be some vision loss but often no noticeable symptoms. It’s not until late AMD that vision loss definitely becomes noticeable.
Why macular degeneration develops is not conclusively known, although scientists believe its causes include both heredity and environment. The biggest risk factor for the disease is age, as it’s most likely to occur in those 55 years and older. Smoking also doubles the risk of macular degeneration.
Macular degeneration is considered an incurable eye disease. To slow the progression of the disease, physicians often recommend lifestyle changes like exercise, avoiding smoking, dieting, and protecting the eyes from ultraviolet light.
Findings: Effects of Cannabis on Macular Degeneration
The effects of cannabis on macular degeneration have yet to be adequately studies, but research indicates that cannabinoids like cannabidiol (CBD) and tetrahydrocannabinol (THC) offer neuroprotective, antioxidant, and anti-inflammatory effects that may be beneficial for improving cell survival in the eyes and encouraging eye health5. Cannabinoids have demonstrated as having neuroprotective properties that may inhibit cell death and vision loss in the case of degenerative eye disorders like retinitis pigmentosa1,6.
An animal study found both CBD and THC effective for limiting the formation of peroxynitrade, a potent oxidant responsible for retinal neuron death2. In another study CBD treatments significantly reduced oxidative stress, decreased the levels of levels of tumor necrosis factor-α, and prevented retinal cell death in the diabetic retina3.
In what further suggests that cannabinoids may be able to play a therapeutic role in patients with degenerative eye diseases, studies have found evidence that cannabinoids increase the light sensitivity of cells in the retina, effectively improving low-light vision7,8.
States That Have Approved Medical Marijuana for Macular Degeneration
No states have approved medical marijuana specifically for the treatment of macular degeneration.
However, in Washington D.C., any condition can be approved for medical marijuana as long as a DC-licensed physician recommends the treatment. In addition, various states will consider allowing medical marijuana to be used for the treatment of macular degeneration with the recommendation from a physician. These states include: California (any debilitating illness where the medical use of marijuana has been recommended by a physician), Connecticut (other medical conditions may be approved by the Department of Consumer Protection), Massachusetts (other conditions as determined in writing by a qualifying patient’s physician), Nevada (other conditions subject to approval), Oregon (other conditions subject to approval), Rhode Island (other conditions subject to approval), and Washington (any “terminal or debilitating condition”).
Recent Studies on Cannabis’ Effect on Macular Degeneration
- THC reduces toxicity in the eye, indicating it possesses neuroprotective effects that inhibit cell death.
Protective effects of Δ9-tetrahydrocannabinol against N-methyl-D-aspartate-induced AF5 cell death.
- THC and CBD reduce the attenuation of peroxynitrate, thereby protecting eye neuron health.
Neuroprotective Effect of(−)Δ9-Tetrahydrocannabinol and Cannabidiol in N-Methyl-d-Aspartate-Induced Retinal Neurotoxicity : Involvement of Peroxynitrite.
- Chen, J., Lee, C.-T., Errico, S., Deng, X., Cadet, J. L., & Freed, W. J. (2005). Protective effects of Δ9-tetrahydrocannabinol against N-methyl-D-aspartate-induced AF5 cell death. Brain Research. Molecular Brain Research, 134(2), 215–225. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1824211/.
- El-Remessy, A.B., Khalil, I.E., Matragoon, S., Abou-Mohamed, G., Tsai, N.-J., Roon, P., Caldwell, R.B., Caldwell, R.W., Green, K., and Liou, G.I. (2003). Neuroprotective Effect of(−)Δ9-Tetrahydrocannabinol and Cannabidiol in N-Methyl-d-Aspartate-Induced Retinal Neurotoxicity : Involvement of Peroxynitrite. The American Journal of Pathology, 163(5), 1997–2008. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1892413/.
- El-Remessy, A.B., Al-Shabrawey, M., Khalifa, Y., Tsai, N.-T., Caldwell, R.B., and Liou, G.I. (2006, January). Neuroprotective and Blood-Retinal Barrier-Preserving Effects of Cannabidiol in Experimental Diabetes. Neurobiology, 168(1), 235-44. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1592672/pdf/JPATH168000235.pdf.
- Facts About Age-Related Macular Degeneration. (2015, September). National Eye Institute. Retrieved from https://nei.nih.gov/health/maculardegen/armd_facts.
- Hampson, A. J., Grimaldi, M., Axelrod, J., & Wink, D. (1998). Cannabidiol and (−)Δ9-tetrahydrocannabinol are neuroprotective antioxidants. Proceedings of the National Academy of Sciences of the United States of America, 95(14), 8268–8273. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC20965/.
- Lax, P., Esquiva, G., Altavilla, C., and Cuenca, N. (2014, March). Neuroprotective effects of the cannabinoid agonist HU210 on retinal degeneration. Experimental Eye Research, 120, 175-185. Retrieved from Macular Degeneration. (2017, August 24). S. National Library of Medicine. Retrieved from http://www.sciencedirect.com/science/article/pii/S0014483514000347.
- Miraucourt, L.S., Tsui, J., Gobert, D., Desjardins, J.-F., Schohl, A., Sild, M., Spratt, P., Castonguay, A., De Konick, Y., Marsh-Armstrong, N., Wiseman, P.W., and Ruthazer, E. S. (2016). Endocannabinoid signaling enhances visual responses through modulation of intracellular chloride levels in retinal ganglion cells. eLife, 5, e15932. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4987138/.
- Russo, E.B., Merzouki, A., Molera Mesa, J., Frey, K.A., and Bach, P.J. (2004, July). Cannabis improves night vision: a case study of dark adaptometry and scotopic sensitivity in kif smokers of the Rif mountains of northern Morocco. Journal of Ethnopharmacology, 93(1), 99-104. Retrieved from http://www.sciencedirect.com/science/article/pii/S0378874104001503.
- What is Macular Degeneration? (n.d.). American Macular Degeneration Foundation. Retrieved from https://www.macular.org/what-macular-degeneration