CBD shows no harmful effects on horse eye health in safety study

This veterinary study examined whether oral cannabidiol (CBD) affects eye health in horses by measuring intraocular pressure (IOP) and tear production. Six healthy adult horses received either 3 mg/kg of CBD or a placebo once daily for three days, with measurements taken at baseline and at 4, 12, and 24-hour intervals after treatment. The study employed a rigorous masked, randomized cross-over design where horses later received the opposite treatment after a five-week washout period to ensure fair comparison.

The results showed that short-term CBD administration had no clinically relevant effects on either eye pressure or tear production in the horses studied. IOP measurements remained stable, and Schirmer tear test values—which assess tear film health—showed no differences between CBD and placebo treatments. The only significant finding was that IOP readings were unexpectedly higher during the second treatment period across both groups, likely a measurement artifact rather than a treatment effect.

While this study focuses on veterinary medicine, it provides valuable safety data for the broader cannabis community. CBD did not negatively impact eye health markers even at therapeutic doses, which is reassuring for users concerned about ocular effects. However, this equine research cannot be directly extrapolated to humans, and more clinical studies in human populations are needed to fully understand CBD's effects on eye health and tear production.