A study has shown that cannabis use can improve night vision. The study, led by Dr Ethan Russo, was inspired by anecdotal reports from Jamaican and Moroccan fishermen, who use cannabis for night sailing because they believe that it improves their ability to see in the dark.
One subject was tested after receiving various doses of oral THC (Marinol) and a placebo. Another three subjects were tested before and after their smoking of cannabis. The researchers found that, "in both test situations, improvements in night vision measures were noted after THC or cannabis." They added that they believed the effect to be "dose-dependent," so that greater quantities of THC would produce increased improvement in night vision.

The testing of night vision was done using a "Scotopic Sensitivity Tester," which allows for vision testing in the field.

The authors call for more research into this area, and suggest possible clinical applications for cannabis in the treatment of eye illnesses, including nyctalopia and retinitis pigmentosa.

? All studies cited were presented at the 2003 Symposium on Cannabinoids, International Cannabinoid Research Society (ICRS). www.cannabis-med.org