THC may delay retinal degradation and vision loss

Cannabis has been used for years for therapeutic purposes to treat eye conditions, particularly to relieve glaucoma, an eye disease in which increased pressure inside the eye gradually destroys the optic nerves, thereby reducing the field of vision. Cannabis is particularly effective at lowering this pressure, thereby improving the vision of those affected—among whom the most famous is undoubtedly Whoopi Goldberg.

A group of researchers from the University of Alicante in Spain demonstrated in a study published in the journal Experimental Eye Research  that cannabinoids might help slow the loss of vision in cases of retinitis pigmentosa.

Retinitis pigmentosa, a congenital disorder, affects approximately 1 in 4,000 people. It causes the death of photoreceptors in the retina and can lead to blindness if left untreated. There is no definitive treatment for this disease, although vitamin A has been shown to be beneficial, delaying blindness by more than 10 years in some patients.

The University of Alicante therefore set out to study the effects of cannabinoid treatments on rats. They were able to slow vision loss using a synthetic form of the tetrahydrocannabinol (THC).

The study group received 100 mg/kg per day of this synthetic cannabinoid and showed significant improvement on the visual tasks compared to the group that did not receive treatment. The rats that received the treatment also had 40% more photoreceptors than the others, which explains why they performed better on tests based on visual stimuli to the brain.

The mechanisms involved in this effect of cannabis on the eye are not yet well understood. The study’s lead author, Dr. Nicolas Cuenca, therefore sticks to the study’s conclusion: «These data suggest that cannabinoids play a potentially beneficial role in delaying retinal degeneration in retinitis pigmentosa.»