A randomized, double-masked, placebo-controlled, 4-way crossover study included six patients to evaluate the effect of oromucosal administration of cannabinoids on intraocular pressure. It was found that intraocular pressure was significantly reduced by THC after two hours, while 20 mg CBD did not produce significant effects and 40mg CBD enhanced intraocular pressure (Tomida et al., 2006).
In eight healthy volunteers, intraocular pressure was reduced by THC (7.5 mg). Retinal blood flow was also shown to be improved by the same cannabinoid (Plange et al., 2007).
In eighteen patients, intraocular pressure was reduced when smoking cannabis (Merritt et al., 1980).