GLAUCOMA BY MICHELLE MARTIN 54
DIS-LIST
Promising results hint that THC might one day treat glaucoma. Glaucoma is an umbrella term for a group of diseases that damage the optic nerve— the signalling pathway bringing color and image information from the retina to the brain.1 Damaged nerve cells in the eye can narrow a person’s field of vision and even lead to complete blindness. According to the World Health Organization, about 4.5 million people are blind as a result of glaucoma in the world—that’s slightly more than 12 percent of all human blindness.2 About three million people who suffer from glaucoma are in the United States, according to the American Glaucoma Society.3 Unfortunately it’s a bit sneaky in that patients often only notice the decrease in their peripheral vision after a large swath of cells is already dead and the disease is in the advanced stages.3,4 Currently, there is no known cure, and patients typically manage the condition for the rest of their lives with medicine, surgery, or both. Although the exact ways in which the diseases work are poorly understood, two aspects are well known: damage to the cells of the optic nerve, and in most cases, there is an increase in pressure within the eye. The most effective medicines used to treat glaucoma aim to lower the pressure within the eye.1,5 Researchers published a study in 1971, in the prestigious “Journal of the American Medical Association” showing that smoking marijuana decreased intraocular pressure.7 We know today that THC is at least one of the components responsible for this effect. Keeping intraocular pressure low seems to work to hold off the worst glaucoma has to offer. Even so, for a minority of patients who are successfully keeping eye pressure low, the disease still progresses. That is why some researchers are looking beyond pressure-lowering medicines and taking a closer look into medications that can also protect the nerve cells from damage4—something THC has also been shown to do.5 THC seems like a good candidate to treat glaucoma because of the combination of its ability to protect neurons as well as lower intraocular pressure. THC affects change in the body by connecting to at least two cannabinoid receptors.7 One of these is the well-known cannabinoid CB1 receptors. They are found throughout the brain and eyes and can affect pain, mood, movement and memory.5,8,9 As it turns out, CBD is actually not well-suited to the job according to results we’ll get to below. Smoking cannabis as a way to treat glaucoma has drawbacks. It lasts a short duration (three to four hours according to the American Glaucoma Society),10 has potentially undesirable psychoactive and other side-effects, as well as the possibility of building up resistance. The society issued a position statement in 2009 saying it does not recommend cannabis for glaucoma treatment. However, the statement hints that the position might change if more promising research becomes available.
