We all know that when we refer to "marijuana" we really mean the dried leaves and tops of the cannabis plant, but not all of us realize that in addition to the chemicals we're accustomed to hearing about - like THC - there are at least 399 other chemical components. This is just one of the reasons cannabis, or more properly, cannabis sativa, has so many medical uses.
One such medical use is in the treatment of glaucoma. Glaucoma is an eye disease that involves increased intraocular pressure that can cause blindness, often by speeding up the growth of cataracts. Cannabis has been shown to reduce the intraocular pressure (IOP) in patients who have POAG, or primary open-angle glaucoma.
Using studies done by the National Eye Institute (NEI) and the Institute of Medicine, as well as on other available information, the Task Force on Complementary Therapies, however, believes that there is no increased benefit or reduced risk that makes marijuana use a more preferred method of treating glaucoma, than any other currently available prescription drugs.
Initial studies completed forty years ago reported that people who smoked pot did have lower IOP for hours after doing so, and research conducted by the NEI also showed that some derivatives of marijuana did result in lowering the IOP when taken orally, intravenously, or via inhalation, but not when applied topically to the eye. The reduced pressure typically lasts for three to four hours, and a side effect - some say a benefit - is a sense of euphoria.
Despite this, there are some adverse effects associated with smoking marijuana, including lowered blood pressure and an increased heart rate. Because some marijuana users in test scenarios have shown reduced blood pressure along with the reduced IOP, researchers as concerned that this may mean blood flow to the optic nerve has been compromised.
At this time, there have been no long-term studies of marijuana as a glaucoma treatment, so most states that allow medical use of marijuana do not include glaucoma as an "allowable condition."