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Reefer Madness? The Truth Behind Medical Marijuana

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The Use of Marijuana to Treat Glaucoma

by Charles M. Lederer, MD

As an ophthalmologist specializing in glaucoma, I am sometimes asked by patients whether marijuana can be used to treat glaucoma. These patients have been made curious by provocative but incomplete, and often inaccurate, media reports suggesting the benefits of this form of treatment.

Glaucoma treatment involves lowering the intraocular pressure (IOP). This helps preserve visual function by slowing or halting progressive damage to the optic nerve. Smoking or ingesting marijuana can, indeed, lower the IOP.1 In addition, THC (marinol), the major psychoactive ingredient in marijuana, has been shown to have an IOP-lowering effect when ingested orally. However, due to a variety of factors, it is not possible to transform these observations into a widespread and clinically useful method of glaucoma treatment at the present time.

The pressure-lowering effects of inhaled marijuana are variable and of short duration. To achieve continuous IOP lowering, this short duration of action requires smoking marijuana every three to four hours.2 The accompanying article describes the cognitive and systemic side effects of regular marijuana use. These side effects proscribe the continuous use of marijuana as a practical way to treat glaucoma.

There might theoretically exist a very rare patient with end-stage glaucoma in whom all methods of medical and surgical treatment have either failed or are contraindicated. Perhaps in this hypothetical isolated case smoking marijuana be considered. However, I have never advised this method of treatment, and I have never spoken with an ophthalmologist who has recommended this. Inhaled marijuana compares poorly to the eye drops we have available to lower IOP. Currently available glaucoma eye drops have been extensively studied and are usually well tolerated and effective. They have a much longer duration of action when compared to inhaled marijuana. A variety of laser and incisional surgical techniques, both established and recently developed, are also available.

Marijuana has a complex composition, containing 60 known cannabinoid compounds. Study of these compounds is ongoing, and it may well be that one or more of these compounds will become a valuable method of glaucoma treatment. At the present, however, despite public fascination with the concept, smoking marijuana as a way to treat glaucoma is not practical, useful and may be a dangerous option.3


References

1. Green, K. Marijuana Smoking vs Cannabinoids for Glaucoma Therapy Arch Ophthalmol. 1998; 116(11):1433-1437.
2. Flack, A. Delta-9-Tetrahydrocannabinol (THC) in the Treatment of End-Stage Open-Angle Glaucoma. Complementary Therapy Assessments. May 2003
3. Primary Open-Angle Glaucoma: Medical Therapy and Surgery. From the American Academy of Ophthalmology Preferred Practice Patterns, November 2010

Dr. Lederer is a glaucoma specialist in Kansas City, Missouri, and the Missouri Medicine Editorial Board member in Ophthalmology. 

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