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Marijuana and Glaucoma

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Updated March 28, 2013

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Many people are wondering about the use of marijuana instead of eye drops to treat glaucoma. Glaucoma is a disease of the optic nerve, the nerve cable that connects the eye to the brain. Glaucoma can cause significant vision loss and even blindness. Most types of glaucoma are caused by high pressure inside the eye. Research has shown that marijuana may be a viable treatment for glaucoma because of its ability to lower the pressure in the eye.

Traditional Glaucoma Treatments

An eye doctor's main goal in the treatment of glaucoma is to lower eye pressure to a safe level in order to halt damage caused by the high pressure levels. Treatment typically includes prescribing medications, using laser treatments, or surgery.

Most glaucoma patients are treated with topical medication eye drops that lower the pressure in the eye to a level where the glaucoma does not progress. Unfortunately, some people do not tolerate daily eye drops very well and additional glaucoma therapies are sought.

Marijuana's Effect on Glaucoma

As several states attempt to legalize the use of marijuana for medicinal uses, it has become a hot topic for glaucoma patients as several studies have shown that smoking marijuana can lower eye pressure in both normal people and those that suffer from glaucoma. People who cannot tolerate typical glaucoma medications may be able to use marijuana to effectively lower their eye pressure.

Downsides of Smoking Marijuana

Scientists have found that marijuana does lower eye pressure but the effects only last for 3 or 4 hours. This means that to lower eye pressure adequately, marijuana would have to be smoked every three hours. Because marijuana causes mood altering effects, smoking it every 3-4 hours would be impossible for people who drive for a living, operate heavy machinery or have jobs that require close attention to detail. Also of great concern is that marijuana cigarettes contain chemical compounds that can damage the lungs similar to regular tobacco cigarette smoking. Studies also show that chronic use of marijuana can have unwanted and sometimes permanent effects on brain function.

Marijuana Eye Drops

If the harmful effects of marijuana are mainly caused by inhalation, could doctors administer the active ingredient, THC (terahydrocannabinol), in a different way? Scientists have conducted studies in which patients ingested THC through oral (by mouth) or sublingual (under the tongue) methods and also in topical eye drops. Although oral or sublingual methods avoid lung problems, they have other unwanted side effects. Because glaucoma is a chronic disease, unwanted systemic side effects make TCH a poor option for treatment. TCH in eye drops sounds like the most logical method of taking the drug. But because TCH is not very water soluble, it has been difficult to develop an eye drop with high enough concentrations of TCH to be effective.

Negative Effects of Marijuana on the Eyes

If oral TCH could be tolerated, more long term studies are needed to make sure that it will not worsen the glaucoma. Research has shown that some glaucoma is worsened by a lack of proper blood flow to the optic nerve. Marijuana actually reduces blood pressure so it is possible that marijuana could worsen the glaucoma by making the optic nerve receive less blood flow.

On the other hand, recent research shows that marijuana may not only treat glaucoma by reducing eye pressure, but it may also act on certain receptors to provide a type of neuro-protection against damage to the optic nerve. This would treat glaucoma in a different way and is worth conducting further studies. Until then, researchers are focusing on a better way to make a THC formulation that people can tolerate and that will have a longer duration of action. For now, glaucoma patients should stick with doctor recommended traditional glaucoma medications.

Source:

Jampel, Henry. Statement of Marijuana and the Treatment of Glaucoma. American Glaucoma Study, 10 Aug, 2009.

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