Humans have appreciated the medicinal value of the cannabis plant for thousands of years. Some of the earliest such accounts date back to 2737 B.C., when Chinese Emperor Shen Neng began recommending cannabis as a treatment for arthritis, gout and – oddly – for overcoming memory problems.
While time has shown that some of these applications were well-founded – arthritis pain, for example, is often treated with cannabis in the modern world – others proved unhelpful in the long term. However, scientists and doctors continue to learn about the medicinal properties of cannabis, including its potential for treating the world’s leading cause of blindness: glaucoma.
First Thing’s First: What Is Glaucoma?
Glaucoma is a progressive condition that causes the internal pressure inside the eye to rise by causing the eye to build up too much vitreous humor – the gelatin-like substance inside the eye that helps keep it round and taught. When the pressure becomes high enough, it can damage the optic nerve.
Typically, this causes sufferers to lose their peripheral vision, which only appears black. Over time, the blackness can encroach across the entire visual field, leaving the afflicted person completely blind.
How Does Cannabis Treat Glaucoma?
Cannabis lowers the pressure in the eyes by allowing the vitreous humor to drain more quickly. It also causes the blood vessels in the eyes to fill with blood, but this is generally considered a minor side-effect.
But cannabis is not a magic-bullet in the fight against glaucoma. While empirical studies have shown that cannabis lowers intraocular pressure, it only appears to do so for about for a short time. After about 4 hours, the intraocular pressure rises back to elevated levels and un-doing any of the good the medication accomplished. Intermittently treating glaucoma is unlikely to lead to meaningful, long-term results – you must treat it constantly.
But, because raw cannabis often causes psychoactive effects, it remains an inappropriate medication for most people. Unless your daily goals are limited to patrolling the couch and consuming candy, ingesting cannabis every four hours may compromise your productivity.
Don’t Throw Out the Baby with the Bathwater
Cannabis is a complex substance with several different active ingredients, called cannabinoids. One such cannabinoid that appears to be of particular medicinal value is cannabinol (CBN). In fact, cannabinol has shown promise in treating ailments as disparate as epilepsy, osteoporosis and the anorexia that often accompanies HIV and chemotherapy patients. It is also an effective anti-bacterial agent, pain-killer and sleep aide.
Given its wide range of therapeutic uses and the fact that mammalian eyes are full of cannabinoid receptors, it should come as no surprise that cannabinol has been proven to treat glaucoma in animal trials.
In 1984, BK Colasanti, CR Craig and RD Allara published a study in the journal Experimental Eye Research, documenting the results of their studies into the medicinal value of cannabinol for treating glaucoma. Although the researchers did not use human test subjects, they did examine the effects of cannabinol in both cats and rats, which are both commonly used as human analogs in such tests. The researchers found that test subjects administered cannabinol exhibited lower intraocular pressure.
Human trials specifically investigating cannabinol have yet to be completed, but it is likely that they will mirror the results of the animal trials. It is already known that cannabis treats glaucoma, and it is very likely that cannabinol is part of the reason it does so. This is especially exciting news, as cannabinol is only weakly psychoactive, which means it can be used in situations in which THC is not appropriate.