Equine Eye Problems: Signs, Causes & Treatment

horses eyes watering

Like all animals, horses are susceptible to a range of health issues, including eye problems. Equine eye problems can be caused by a variety of factors, including infections, injuries, and genetic predisposition. These eye problems can lead to discomfort and pain, and if left untreated, can result in vision loss. In this article, we will discuss some of the most common equine eye problems, their signs and symptoms, and how they can be diagnosed and treated.

The Horse’s Eye

The horse’s eye is a complex and delicate structure that allows the animal to see clearly both in bright sunlight and in low light conditions. It is located on the side of the head, providing the horse with a wide field of vision, including almost 360-degree vision. The equine eye is protected by a bony orbit and a third eyelid, which is a thin, semi-transparent membrane that moves across the eye to keep it clean and moist.

The equine eye is larger than that of most other mammals, and it has a larger cornea and a deeper anterior chamber. Additionally, the horse’s eye contains a tapetum lucidum, a reflective layer behind the retina that helps improve their vision in low light conditions. The equine eye is also very sensitive to light, and a horse’s pupils are capable of expanding and contracting rapidly to adapt to changes in light intensity.

Signs of Eye Problems in Horses

There are several signs and symptoms of eye problems in horses that owners should be aware of. These can include:

  • Discharge: Discharge from the eyes is a common sign of an eye problem in horses. The discharge can be watery or thick and can be clear, yellow, or green in color. Excessive watery eyes in horses may indicate an infection or injury.
  • Redness: Redness around the eye or on the white part of the eye can be a sign of inflammation or infection.
  • Swelling: Swelling around the eye can be a sign of trauma or infection.
  • Squinting: Horses may squint or close one or both eyes when they are experiencing discomfort or pain.
  • Cloudiness: Cloudiness or opaqueness of the eye can indicate a cataract or other condition that affects vision.
  • Excessive tearing: Horses may produce excessive tears in response to an eye injury or infection.
  • Sensitivity to light: Horses with eye problems may be sensitive to light and avoid bright areas.
  • Changes in behavior: Horses may exhibit changes in behavior such as rubbing their eyes or shaking their heads in response to discomfort or pain.

Common Horse Eye Problems

There are several common equine eye conditions that horse owners should be aware of. These include:

  • Conjunctivitis: Conjunctivitis, also known as “pink eye,” is an inflammation of the conjunctiva, the thin membrane that covers the white part of the eye and the inside of the eyelids. This condition can be caused by bacteria, viruses, allergies, or irritants. Symptoms can include discharge, redness, and swelling.
  • Recurrent Uveitis: Recurrent uveitis, also known as “moon blindness,” is a condition characterized by inflammation of the uvea, the middle layer of the eye. This condition can be caused by autoimmune diseases, infections, or trauma. Symptoms can include tearing, squinting, and cloudiness of the eye.
  • Injury & Allergies & Herpes Virus: Eye injuries, allergies, and herpesvirus can cause various eye conditions in horses. Eye injuries can range from minor scratches to more serious injuries such as corneal ulcers or lacerations. Horse eye allergies can cause conjunctivitis, while herpesvirus can cause severe inflammation of the eye and other respiratory and neurological symptoms.
  • Eye Worms: Equine eye worms, also known as Thelazia, are parasitic worms that can infest the eye tissues of horses. Symptoms can include discharge, swelling, and squinting.
  • Cataracts: Cataracts are a clouding of the lens of the eye, which can cause vision loss. This condition can be genetic or can develop as a result of injury or disease.
  • Keratomycosis: Keratomycosis is a fungal infection of the cornea, which can cause cloudiness and ulceration of the eye. This condition is more common in horses living in warm, humid environments.
  • Periocular Melanoma Tumors: Periocular melanoma tumors are a type of skin cancer that can affect the tissues around the eye. These tumors are more common in gray horses and can cause vision loss if left untreated.

Diagnosing and Treating

Diagnosing and treating eye problems in horses requires a thorough understanding of equine anatomy and physiology, as well as specialized training and equipment. If you suspect that your horse is experiencing an eye problem, it is important to consult with your veterinarian as soon as possible.


To diagnose an eye problem in a horse, a veterinarian will perform a thorough physical examination of the eye and surrounding structures. This may involve the use of specialized equipment, such as a slit lamp biomicroscope, which allows for detailed examination of the cornea, iris, and other structures within the eye.

Additional diagnostic tests that may be performed include:

  • Fluorescein staining: This test involves the use of a dye to detect any corneal ulcers or abrasions.
  • Tonometry: This test measures the pressure within the eye and can help diagnose conditions such as glaucoma.
  • Schirmer tear test: This test measures the production of tears and can help diagnose conditions such as dry eye.
  • Blood tests: In some cases, blood tests may be performed to check for underlying systemic conditions that may be contributing to the eye problem.


Treating eye problems in horses can be challenging and requires prompt and appropriate intervention to prevent the problem from worsening or causing permanent damage to the eye. The treatment for eye problems in horses varies depending on the underlying cause of the issue.

  • Bacterial Infections: If the eye problem is due to a bacterial infection, then antibiotics are usually prescribed in the form of eye drops, ointments, or oral medication. It is important to continue the treatment for the full course, even if the symptoms have resolved.
  • Viral Infections: There is no cure for most viral eye infections, so treatment is primarily supportive. The vet may recommend anti-inflammatory drugs, antiviral medication, or immunomodulators to control the symptoms and support the horse’s immune system.
  • Fungal Infections: Treatment of fungal infections in the horse’s eye usually involves a combination of topical and systemic antifungal medication. Surgery may be necessary if the infection has caused significant damage to the eye.
  • Allergies: If the eye problem is due to allergies, then identifying and removing the allergen is the first step in treatment. If the horse has an allergic reaction to insect bites, then topical or systemic antihistamines may be prescribed by the vet to manage the symptoms.
  • Trauma or Injury: Treatment of traumatic injuries to the horse’s eye will depend on the severity of the injury. Mild injuries may be treated with topical medications, whereas severe injuries may require surgery to repair the damage.
  • Tumors: Treatment of tumors in the horse’s eye usually involves surgical removal of the tumor. Chemotherapy or radiation may be recommended by the vet depending on the type and severity of the tumor.


Overall, equine eye health is an essential aspect of the horse’s overall health and well-being, and it is crucial for horse owners to be vigilant about eye problems and seek prompt veterinary care when necessary to help ensure the horse’s optimal health and quality of life.

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