Finding the Light – Your Guide to your Horse and Uveitis

Shannon Wilkens

Chemist specializing in Cannabis

Are you scared your beloved horse has Uveitis? Maybe your horse has already gotten this seemingly terrifying confusing diagnosis and you want to understand uveitis better.

Uveitis is the leading cause of blindness in horses. In this comprehensive guide, we will explore what causes uveitis, its symptoms, and how you can help your horse stay healthy and happy.

Note: This guide complements veterinary advice. For your horse’s health, always consult a professional. Brave Horse CBD can support alongside medical care.

The Basics of Uveitis: What You Need to Know

Uveitis affects 2-25% of horses globally, and it can affect any horse, leading to pain and potentially blindness. The condition is marked by inflammation within the eye’s uveal tract, which is the blood vessel-filled tissue beneath the sclera (white of the eye). This leads to severe and often irreversible visual impairment.1Young, A. Equine Recurrent Uveitis 2Thomasy, S. Overview of Equine Recurrent Uveitis

While some horses may experience sporadic flare-ups, others endure continuous inflammation, culminating in cataracts, glaucoma, and eventual blindness.3Young, A. Equine Recurrent Uveitis

Common Symptoms of Uveitis in Horses

  • Squinting, indicating discomfort or pain.
  • Tearfulness and mucous discharge, signaling irritation.
  • Sensitivity to light, leading to noticeable discomfort in bright environments.
  • Swelling or redness of the eye(s), often accompanied by a puffy or swollen eyelid.
  • Cloudy appearance or bluish haze over the cornea, possibly with bloodshot sclera.
  • Presence of pus or yellow deposits under the cornea in the eye’s anterior chamber.
  • Periods of acute discomfort due to inflammation, interspersed with phases of apparent normalcy.
  • Navigational difficulties, such as horses running into objects, increased spooking, and trouble with terrain.
  • In severe or unchecked cases, progression to blindness, often without prior noticeable symptoms.

Causes and Types: Understanding Uveitis

Uveitis can occur as a one-off event, for example, an incident that causes trauma to the eye. However, most cases of uveitis are categorized as recurrent. Although the symptoms and damage uveitis causes can wax and wane, it is generally a progressive condition, leading to permanent damage and eventually blindness.

What Triggers Uveitis in Horses?

Different types of infections as well as physical trauma to the eye can cause ERU (Equine Recurrent Uveitis), and the physiologic factors that cause the symptoms of the disease are complex and multifaceted.

Uveitis is also more common in humid regions, areas with high precipitation, as well as areas with clay and marsh-type soils.

What is the Biggest Cause of Uveitis?

The biggest cause is inflammation and degeneration as a result of oxidative stress—the imbalance between reactive oxygen species (ROS) and antioxidants in the body.4Betteridge, D. J. What Is Oxidative Stress? Metabolism 2000, 49 (2), 3–8. The most common infectious trigger is leptospirosis. We will explain more about this root cause later in this article.

Classic ERU 

This is the most common form of uveitis, characterized by periods of inflammation, followed by periods of dormancy. With each inflammatory phase, the disease progressively worsens.
Most common in warmbloods and Icelandic horses.

Insidious ERU

In this type, the inflammation never completely resolves and does not typically cause discomfort. This form of uveitis leads to the gradual destruction of ocular tissues and degeneration of structures in the eye. Owners may not realize there is an issue until their vision is severely impaired.
Most common in appaloosa and some draft breed horses.

Posterior Uveitis

Posterior uveitis is characterized by changes and degeneration in the vitreous fluid and retina of the eye. The inflammation is mainly in the back or posterior part of the eye, hence the name.
Most common in warmbloods and horses in Europe.

The Real Root Issue: Oxidative Stress

Uveitis often stems from oxidative stress, which occurs when there’s an imbalance between reactive oxygen species (ROS) and protective antioxidants in the body.5Betteridge, D. J. What Is Oxidative Stress? Metabolism 2000, 49 (2), 3–8. ROS are normal byproducts of cell activities, like turning food into energy (ATP). However, if there aren’t enough antioxidants to neutralize these ROS, they build up and trigger harmful responses that can damage cells over time.

This imbalance leads to the activation of p38 mitogen-activated protein kinase (MAPK), a key enzyme in cell signaling that responds to environmental changes.6Anerillas, C.; Abdelmohsen, K.; Gorospe, M. Regulation of Senescence Traits by MAPKs. GeroScience 2020, 42 (2), 397–408. In Equine Recurrent Uveitis (ERU), this ongoing oxidative stress fuels inflammation and the gradual deterioration of the eye.

What to Do if You Suspect Uveitis

Your first step: call your veterinarian immediately. As we have already explored, there are many causes and types of uveitis. It’s important to rule out causes such as infection, an eye ulcer, trauma to the eye area, and other time-sensitive issues.

Early intervention can make a big difference in managing uveitis and protecting your horse’s vision.

What is the Best Treatment for Uveitis in Horses?

For ERU the most common treatments recommended are focused on combating inflammation and preserving vision through a regimen of topical corticosteroids, NSAIDs, and mydriatic drugs but these do not prevent reoccurrence.

In severe cases, corticosteroid injections, cyclosporine implantation, core vitrectomy (removal of debris and replacement with saline), or enucleation (eye removal) may be necessary.7Young, A. Equine Recurrent Uveitis 8Thomasy, S. Overview of Equine Recurrent Uveitis

Despite these efforts, these treatments manage symptoms and do not address the underlying root cause of ERU.

The Incredible New Research of CBD to Help Horses with Uveitis 

Seeing a veterinarian and seeking out conventional treatments are critical, but emerging research is positively showing Cannabidiol (CBD) can give amazing benefits, transforming horses with uveitis and giving horses their life back. Here are some of the ways CBD can fight uveitis at its root:

  • As a potent antioxidant properties, CBD has been shown to reduce inflammation and degeneration.
  • CBD gets to the root of ERU by reducing oxidative stress and directly inhibiting p38 MAPK.9Liou, G. I.; Tang, Y.; Hanson, E.; Matragoon, S.; Liu, E. K.; Mian, S.; Zhu, G.; Khalifa, Y.; Caldwell, R. B.; ElRemessy, A. B. Neuroprotective Effect of Cannabidiol in Endotoxin-Induced Retinal Inflammation. Investigative Ophthalmology & Visual Science 2007, 48 (13), 4954–4954. 

CBD’s antioxidant, anti-inflammatory, and neuroprotective properties make it a promising potential treatment for ERU as it treats not only the symptoms of the disease but also the underlying causes as well. You can read more about the recent studies done for horses and uveitis here.

How You Know Your CBD is Safely Made with Care and Love

CBD is a natural, non-invasive approach to supplement your horse’s ERU condition management. Our CBD is grown in the USA, THC-free, and third-party tested with the highest standards to ensure safety and efficacy. Our handcrafted range of products are made in-house and in small batches for quality control. 

Brave Horse’s Commitment to All Horses

Our mission has always been created by horse owners and lovers like you who are passionate about optimizing your horse’s wellness and bringing joy to their lives.

Together, we can work towards maintaining your horse’s health and happiness. Understanding uveitis in horses and its management is essential for proactive care. With the addition of new emerging research on CBD, you can gain an innovative treatment to preserve your horse’s sight and help create a Calm, Brave, and Dependable horse.

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About the author


Shannon holds a B.S. in Chemistry from Loyola University Chicago and began her journey in cannabis chemistry in 2018. Passionate about cannabis science, she developed protocols for in-house testing, established cannabis testing and research labs across the USA, and trained future chemists.

At Brave Horse, Shannon serves as a chemist, ensuring product quality and championing the benefits of cannabis through chemistry education. Outside of work, she cherishes moments with her family and her playful boxer, Chance.

If you have any burning questions, she loves to answer anything chemistry-related!


Shannon Wilkens

Chemist specializing in Cannabis

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