A new study has found that a specially formulated cannabidiol (CBD) eye treatment significantly reduced intraocular pressure in rabbits, offering promising evidence for its potential use in treating glaucoma and other eye disorders.
The study, accepted October 23 for publication in the International Journal of Biological Macromolecules, was conducted by researchers at the University of Florence in Italy. Researchers developed a CBD delivery system designed to overcome one of the biggest challenges of cannabinoid-based eye treatments: getting sufficient amounts of CBD into the eye before tears wash it away.
The treatment combines CBD-loaded nanoparticles coated with chitosan, a naturally derived compound that helps medications adhere to biological surfaces, with a temperature-sensitive gel. The formulation remains liquid at room temperature but transforms into a gel within approximately 15 seconds after reaching the eye’s surface, potentially allowing CBD to remain in contact with ocular tissues longer.
Researchers tested the formulation in New Zealand White rabbits, including animals with normal eye pressure and those with experimentally induced elevated pressure.
In rabbits with normal eye pressure, a single application containing 15 micrograms of CBD reduced average intraocular pressure from 19.4 mmHg to 17.2 mmHg after 60 minutes. The reduction of 2.2 mmHg was statistically significant (p<0.0001), with a significant effect also observed after 120 minutes.
The researchers also measured CBD concentrations in the fluid inside the eye, finding that levels peaked at 21.7 nanograms per milliliter after 60 minutes. This coincided with the greatest reduction in eye pressure, suggesting that the treatment successfully delivered CBD to the intended tissues.
In rabbits with temporarily elevated eye pressure, the CBD formulation performed better than an identical treatment without CBD. After 120 minutes, average pressure was 21.7 mmHg in CBD-treated eyes compared with 23.2 mmHg in control eyes. When adjusted for baseline differences, the CBD treatment produced an additional 1.9 mmHg reduction.
Safety testing also produced encouraging results. Researchers administered the formulation daily for five consecutive days and monitored the rabbits afterward, finding no observable irritation of the cornea, conjunctiva or iris. Laboratory experiments using human corneal cells generally supported its short-term tolerability, although higher concentrations reduced cell viability during prolonged exposure.
Elevated intraocular pressure is a major risk factor for glaucoma, a disease that damages the optic nerve and can cause irreversible vision loss. Treatments that reduce eye pressure are commonly used to slow disease progression, making the findings potentially relevant to future glaucoma therapies.
The researchers emphasized that additional studies are needed to evaluate the treatment’s effectiveness and safety during prolonged use. The animal experiments involved six rabbits, and the researchers have not established whether the formulation would produce similar results in humans.
Nevertheless, the findings demonstrate that CBD can be delivered directly into the eye through a temperature-sensitive formulation while producing measurable reductions in intraocular pressure. Researchers plan to investigate its effectiveness in chronic disease models and determine whether higher CBD concentrations can improve its therapeutic potential.
