Purpose: The purpose of this study was to assess the effect on intraocular pressure (IOP) and the safety and tolerability of oromucosal administration of a low dose of delta-9-tetrahydrocannabinol (Delta-9-THC) and cannabidiol (CBD).
Patients and methods: A randomized, double-masked, placebo-controlled, 4 way crossover study was conducted at a single center, using cannabis-based medicinal extract of Delta-9-THC and CBD. Six patients with ocular hypertension or early primary open angle glaucoma received a single sublingual dose at 8 AM of 5 mg Delta-9-THC, 20 mg CBD, 40 mg CBD, or placebo. Main outcome measure was IOP. Secondary outcomes included visual acuity, vital signs, and psychotropic effects.
Results: Two hours after sublingual administration of 5 mg Delta-9-THC, the IOP was significantly lower than after placebo (23.5 mm Hg vs. 27.3 mm Hg, P=0.026). The IOP returned to baseline level after the 4-hour IOP measurement. CBD administration did not reduce the IOP at any time. However, the higher dose of CBD (40 mg) produced a transient elevation of IOP at 4 hours after administration, from 23.2 to 25.9 mm Hg (P=0.028). Vital signs and visual acuity were not significantly changed. One patient experienced a transient and mild paniclike reaction after Delta-9-THC administration.
Another potential application of cannabinoids in ocular health is Macular Degeneration. (MD) Yet another leading cause for vision loss in the USA.
A textual reference 8 discusses that a non-randomized study in healthy volunteers compared with glaucoma patients showed temporary reductions in IOP with oral, topical eye drops, and intravenous administration of cannabinoids. And, it also points out that systematic reviews concluded that the trial was unclear.
CBD-infused eye drops are considered favorable in treating neuropathic ocular pain or diabetic retinopathy (eye complications due to diabetes).
Additionally, reference from two studies is mention-worthy here.
CBD Eye drops for macular degeneration
1.The 2018 study 5 tested and compared the results of IOP on rats after independently administering eye drops containing THC and CBD.
According to a 2008 study 9 abundant growth of vascular endothelial growth factor (VEGF) proteins is the major cause of abnormal blood vessel growth in the retina.
2. A 2006 randomized study 6 examined six glaucoma patients for IOP levels after sublingual administration of THC and CBD. Here too, similar results as the above study are reported. They are:
CBD drops and eye dryness
Furthermore, a 2019 study 7 points out that while the use of CBD for several diseases is growing, it lacks sufficient scientific evidence to prove its efficacy.
Although scientific references signify that smoking cannabis with a high THC potent lowers intraocular pressure of glaucoma, developing eye drops with cannabis compounds has been a challenge because of its lipophilic nature.