Akorn Animal Health

Equine Cataracts Equine Corneal Ulcers

The cornea is the clear dome shaped structure that forms the front surface of the eye and allows light to enter the eye for functional vision. It protects the structures inside the eye and maintains ocular shape and integrity. Corneal ulcers occur with the loss of the outer layer, or epithelial surface, of the eye.

Ulcers can be caused by:

  • Trauma
  • Lacerations or abrasions
  • Drying due to abnormal tear production
  • Eyelid or eyelash abnormalities
  • Foreign material
  • Parasites
  • Viral or bacterial infections
  • Insect stings
  • Chemical sprays
  • Inflammation

In some cases, the initial cause cannot be determined. Signs of ulceration include a combination of squinting, increased tearing, discomfort, discharge from the eye, redness and sensitivity to light. Cloudiness of the cornea or discoloration may be noted.

Within days, a superficial, uncomplicated ulcer should heal uneventfully with minimal scarring after initial therapy provided by your veterinarian, however, a corneal ulcer can become secondarily infected with bacteria, fungi, or a mixture of the two. Infected or complicated ulcers require more intensive treatment. Corneal samples for cytology or cultures may be recommended. This may help determine a potential infectious agent and appropriate therapy.

In complicated cases, the ulcer may rapidly deepen or the cornea may start a breakdown process called melting. A melting cornea can potentially lead to rupture of the eye. Melting and deep ulcers are considered eye emergencies. Secondary inflammation (uveitis) inside the eye usually develops. A deep or infected ulcer and the associated inflammation can be vision-threatening. The ulcer may require intensive treatments for several days to weeks to control infection, reduce melting and control inflammation in order to potentially heal and save the eye. Deep and complicated corneal ulcers can result in more noticeable scarring after healing. Large or dense white scars can cause visual impairment and affect the horse’s athletic performance.

Deep or melting ulcers, or ulcers that worsen despite therapy, may require surgery in addition to medical therapy to prevent rupture of the eye. These surgeries usually involve grafting additional supportive tissue, such as a flap of conjunctiva (tissue from the “pink” part of the eye), into the ulcer. This helps to fill in the tissue defect and hasten healing. These grafts usually incorporate into the corneal tissue in a few weeks, but may result in a dense scar.

A lavage tube may be surgically implanted to assist you in treating the eye appropriately. The lavage tube is particularly useful if the eye is very painful, infected, or the horse becomes resistant to handling. This is especially important in the immediate period after surgery when the graft is susceptible to trauma. While being treated for a corneal ulcer, it helps to keep the horse in a darkened stall or barn and to limit activity and rubbing. A fly mask or Eye Saver mask may also be used to protect the eye. Minimizing exposure to dust by sprinkling the stall with water twice daily and keeping the horse out of the wind or blowing sand is important. Removing hay from overhead racks and feeding soaked hay on the ground is also helpful.

If you have any question about this information please contact your veterinarian.