Moonblindness in Horses

by Staff Writer

Horses, majestic creatures known for their strength and resilience, can sometimes face health challenges that require our attention and care. One such ailment is moonblindness, scientifically known as Equine Recurrent Uveitis (ERU). This eye condition can affect horses of all breeds and ages, and it’s essential for horse owners, veterinarians, and equestrians to understand its causes, symptoms, and treatment options.

What is Moonblindness?

Moonblindness, or Equine Recurrent Uveitis (ERU), is a recurrent inflammatory eye disease that primarily affects a horse’s uvea—the middle layer of the eye. This condition can lead to discomfort, vision impairment, and, in severe cases, blindness if left untreated. Moonblindness is so named because it was once believed that the moon’s phases had an influence on the condition, though it has since been disproven.

Causes of Moonblindness

ERU has a multifactorial origin, with no single definitive cause. However, several factors are thought to contribute to its development:

1. Autoimmune Response: Researchers believe that an autoimmune response plays a significant role in ERU. The immune system mistakenly identifies components within the eye as foreign invaders and mounts an immune response, leading to inflammation.
2. Genetic Predisposition: Certain horse breeds, such as Appaloosas and Warmbloods, are more prone to developing ERU, indicating a genetic predisposition.
3. Environmental Triggers: Environmental factors, including infections (bacterial or viral), trauma, and exposure to allergens, can trigger the onset of ERU.
4. Stress: Prolonged stress or illness can weaken a horse’s immune system, making it more susceptible to ERU.

Symptoms of Moonblindness

Recognizing the early signs of ERU is crucial for prompt intervention and better treatment outcomes. Common symptoms include:

• Excessive Tearing: Increased tearing or watery discharge from one or both eyes.
• Squinting: Horses with ERU often squint or partially close the affected eye due to discomfort.
• Redness: Inflamed eyes may appear red or bloodshot.
• Photophobia: Horses with ERU are sensitive to light and may seek shade or darken their surroundings.
• Cloudiness: The affected eye may become cloudy or develop corneal edema.
• Constricted Pupil: The pupil may appear smaller than usual.

Treatment and Management

While there is no cure for ERU, early diagnosis and proper management can help control the condition and preserve the horse’s vision. Treatment options include:

1. Anti-inflammatory Medications: Non-steroidal anti-inflammatory drugs (NSAIDs) and corticosteroids are often prescribed to reduce inflammation and pain.
2. Immunosuppressive Drugs: In some cases, medications that suppress the immune response may be necessary to prevent flare-ups.
3. Antibiotics: If an underlying bacterial infection is suspected, antibiotics may be prescribed.
4. Surgery: In severe cases or if complications like glaucoma develop, surgical interventions may be considered.
5. Environmental Management: Reducing exposure to known triggers, such as allergens or excessive sunlight, can help prevent flare-ups.
6. Regular Eye Exams: Frequent eye examinations by a veterinarian are crucial for monitoring the condition and adjusting the treatment plan as needed.

Moonblindness, or Equine Recurrent Uveitis, is a challenging eye condition that can affect horses of various breeds and ages. While it cannot be cured, early diagnosis, appropriate treatment, and diligent management can help maintain a horse’s eye health and preserve its vision. Horse owners, veterinarians, and equestrians must remain vigilant for the early signs of ERU and seek professional care to ensure the well-being of these magnificent animals. With proper care and attention, horses affected by moonblindness can lead comfortable lives and continue to enjoy their equestrian activities.