What are Corneal Ulcers?
Any time a corneal ulcer develops, bacterial and fungal infections must be considered. Bacteria can cause a melting ulcer, while a fungal invasion can result in at least 25% of vision loss, even with treatment. In all kinds of ulcers, iris and eye inflammation are present, and must be treated to preserve vision. The deeper an ulcer goes, the longer healing time will be, with possible corneal scarring, or even loss of an eye. If you notice any eye issue in your horse, prompt medical attention is needed, no matter how small the actual problem may seem.
Corneal ulcers, or ulcerative keratitis, are breaks or abrasions in the layers of the cornea that can cause an inflammation, or keratitis. They can range from superficial injuries that affect only the epithelium, or topmost layer of the cornea, to deep perforations in the cornea that may cause an iris prolapse. Although they may initially appear mild, without treatment corneal ulcers can threaten the sight of an affected horse.
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Symptoms of Corneal Ulcers in Horses
Symptoms of a corneal ulcer are:
- Cloudiness or blue in the cornea
- Red or swollen eye
- Inability to tolerate bright sunlight
- Eye pain
- Decreased vision
- Eye darkening
Ulcers can be classified by the depth of the ulceration, or by the cause. Some types include:
These type of ulcers or abrasions are not very deep, often involving only epithelial cell loss. If there is no infection, they can heal quickly.
This type of ulcer is deeply infected, and causes white blood cells that produce enzymes to flood the area. Often in response to a bacterial infection, these enzymes progress the ulcer more quickly by digesting the collagen in the stroma, a layer of the cornea. It is characterized by a liquefied, grayish appearance surrounding the ulcer.
This ulcer penetrates the Descemet’s membrane, the lowest layer of the cornea. These are deep ulcers that require immediate medical assistance, as the cornea can rupture, causing the iris to prolapse.
Equine Ulcerative Keratomycosis
This is an ulcer caused by a fungal invasion.
Causes of Corneal Ulcers in Horses
Causes of a corneal ulcer can include:
- Foreign bodies, such as dirt
- Eyelid disease
- Bacteria, such as Pseudomonas, Staphylococcus, and Streptococcus
- Fungal infection
- Herpesvirus infection
Diagnosis of Corneal Ulcers in Horses
After a complete eye exam, your veterinarian will use various testing methods to correctly diagnose an ulcer. Your horse’s eye will be stained using a fluorescent dye to better see the ulcer itself. A corneal cytology will be done. Cultures will be taken and tested for the presence of bacteria. If a fungal infection is suspected, the presence of fungal cells in the cornea can confirm it.
If an ulcer is infected, melting, healing slowly, or not responding to treatments, antibiotic sensitivity tests may be performed, as well as additional culture tests.
Treatment of Corneal Ulcers in Horses
Treatment will depend on the depth of the ulcer and severity of infection, and must be administered as quickly as possible to prevent vision or eye loss. Small, superficial ulcers can be treated with broad spectrum or species-specific antibiotics. Topical atropine is used to dilate the eye, and pain medication is given to reduce eye pain. This should resolve the ulcer within 10 days.
If a melting, deep, or infected ulcer is present, it will need more treatments on top of those already listed. Anti-collagenase and antiprotease therapy is administered, such as autologous serum, and can be given in a subpalpebral lavage system. This is tubing placed through the eyelid to allow frequent or long term therapy. In the case of a melting ulcer, anti-enzymatics may be administered, and surgery may be recommended to graft healthier eye tissue over the ulcer to promote healing.
In slow healing ulcers caused by the herpes virus, the damaged, dead, or infected ulcerous tissue is removed, then treated with topical medication.
In the case of a fungal infection, antifungal medication will be prescribed. A fungal ulcer often does not respond to the first round of treatment, and can take months to clear, causing more pain for your horse. Surgery to transplant a healthy cornea from a donor horse may be recommended in severe cases.
Surgery may also be recommended in cases of a descemetoceles ulcer that cause the iris to prolapse, with deep ulcers that can cause eye rupture, or to increase corneal thickness. If the eye does rupture, it can cause further illness and pain for your horse, as well as eye loss. In such cases, removal of the eye can be recommended.
Recovery of Corneal Ulcers in Horses
The rate of recovery will vary, depending on the depth of the ulcer, the severity of infection, and the cause of the ulcer in your horse. While superficial ulcers can heal in just over a week with proper treatment, more severe cases can see scarring in the eye, treatments that continue over months, and even vision or complete eye loss. Your veterinarian will discuss what you should expect to see in your horse’s recovery based on his specific case.
If you are treating your horse for the ulcer at home, you may be given medications to administer. Be sure to keep your horse in low lighting until the ulcer is healed. Feed your horse hay on the ground to prevent debris from getting into his healing eye. You may also use a fly mask to protect the eye from debris, flies, and any further trauma.
Corneal Ulcers Questions and Advice from Veterinary Professionals
I have a 27 year old gelding who has a deep ulcer in his eye. My vet has prescribed several medications including serum from his blood, moxifloxicin, Polysporin for eyes and vorcanazole for fungal infection. It has been a month now, and although the ulcer is not getting worse, it seems to be slow in healing. He is not in pain or discomfort and has some vision. He has now contracted a small ulcer in the other eye which we are treating with antibiotics. I give the meds every 2 hours 12 hours a day
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