"In an effort to determine whether marijuana, or drugs derived from marijuana, might be effective as a glaucoma treatment, the National Eye Institute (NEI) supported research studies beginning in 1978... However, none of these studies demonstrated that marijuana -- or any of its components -- could lower IOP [intraocular pressure] as effectively as drugs already on the market. In addition, some potentially serious side effects were noted, including an increased heart rate and a decrease in blood pressure in studies using smoked marijuana.

The identification of side effects from smoked marijuana, coupled with the emergence of highly effective FDA-approved medications for glaucoma treatment, may have led to diminished interest in this research area."

-- National Eye Institute
"Glaucoma and Marijuana Use," nei.nih.gov
Mar. 17, 2009