Glaucoma is a disease and eye condition in which the optic nerve becomes damaged over time, reducing side vision and sometimes causing blindness. One cause of optic nerve damage is higher-than-normal pressure within the eye (intraocular pressure or IOP). The only cure for glaucoma is to lower the IOP levels.
In low-tension or normal-tension glaucoma, optic nerve damage and narrowed side vision occur in people with normal eye pressure. In some people, lowering the eye pressure at least 30 percent through medicines can slow the disease. However, glaucoma may worsen in others despite low pressures.
Glaucoma can develop as a complication of other medical conditions. Some severe forms of the disease can result from high blood pressure or poorly controlled diabetes. Other types of glaucoma can occur with cataract, certain eye tumors or when the eye is inflamed or irritated by a condition called uveitis. Glaucoma can also develop after eye surgery or serious eye injury. Steroid drugs used to treat eye inflammations and other diseases can trigger glaucoma in some people.
How Cannabis Can Help Relieve Symptoms
Treating glaucoma with cannabis dates back to the 1970s when research found that cannabis and its active ingredient THC lowered IOP levels. Some studies showed a 60% to 65% drop in IOP in both “normal” individuals and patients with glaucoma.
Along with the dramatic benefits come some drawbacks, such as the short period of time it’s effective in lowering IOP: three to four hours. Patients would need to take medication six or eight times a day around the clock to receive the benefit of lowered IOP. This quantity of medication could come with several unwanted side effects. While cannabis can lower IOP levels, it can also lower blood pressure throughout the body. As a reduced flow of blood to the optic nerve may cause damage in patients with glaucoma, the benefit of cannabis in lowering IOP levels might be cancelled out by the reduced flow of blood. Scientists are continuing to investigate the benefits, limitations and side effects of using medical cannabis to treat glaucoma.