Equine corneal ulcers are the most common type of ocular ailment. Corneal ulcerations are considered quite serious and can threaten a horse’s eyesight if not adequately treated. Even a small ulcer can quickly develop into something much worse. It is thus important that immediate attention be given and treatment administered. When a horse develops a corneal ulcer, the outer layers of the cornea have been lost and the stroma exposed. This loss might be due to trauma or an inflammatory condition.
Causes
Experts have yet to be able to pinpoint an exact cause for the development of corneal ulcers. However, many believe that they occur after an injury to the eye has occurred. Horses, unfortunately, are quite prone to them. This may have something to do with their height in relation to other animals, people, trees, etc. Facial nerve paralysis might cause corneal ulcers or at least may be related to their development. The embedding of debris in the eye can also cause ulceration. A horse may injury its eye while in a stall, while being ridden on a trail, blunt trauma. Flying debris may also get into a horse’s eye and cause problems.
Fungal and bacteria infections are always a risk after a horse develops a corneal ulcer. Horses are at risk of developing very serious infections such as Staphylococcus, Pseudomonas and Streptococcus. It is important that they are treated as soon as they are detected. Most veterinarians will prescribe an antibiotic as soon as the horse is diagnosed with a corneal ulcer in an effort to head off related or secondary infections.
Symptoms
When a horse develops a corneal ulcer, it will experience a great deal of ocular pain. It may also develop conjunctivitis and corneal inflammation. Tearing, constricted pupils, corneal edema, discharge, light sensitivity, eye-lid spasm and head shyness are additional symptoms.
Diagnosis
Before it can be stated with certainty that a horse has a corneal ulcer, the condition must first be diagnosed. A veterinarian may sedate the horse or give it a nerve block to ease any pain and/or discomfort that may occur during the exam.
The veterinarian will first perform an ocular exam. The surfaces of the cornea will be examined with a diffuse light. A culture swab may then be taken or the cornea scraped. If the latter is deemed necessary, the horse will be given both a block and medication so that they don’t feel it. Staining the eye with either Rose Bengal or Fluoroscein is often recommended. The former is commonly used for the diagnosis of corneal ulcer. The latter, Rose Bengal
Staining may also be performed in order to determine whether any fungal or viral lesions are present. If a corneal ulcer is severe or seems to be quickly getting worse, culture and sensitivity tests may be ordered.
One of the most common occurring complications present with corneal ulcers is a secondary uveitis. If secondary uveitis occurs, an accumulation of fluid in the cornea may develop, along with miosis, IOP changes and aqueous flare.
The manner, in which a horse which has corneal ulceration is treated, depends on the severity of the ulcer. A vet will likely prescribe antibiotics first. Topical medications may be given as well. If the ulcer is resistant to treatment, it may be necessary to insert a sub-palebral lavage system. During and after treatment, an eye mask may be required to help protect the eye from future trauma.
Because the condition is so painful, horses may make contact with their eyes, in an attempt to rub them. This puts the already compromised eye in additional danger. Aside from treatment, and physically covering the eye, it may necessary to force the horse to rest. If it does not and it exerts itself, it is possible that intra-ocular hemorrhage may occur. The uveitis may also become more severe.
If the treatment of a corneal ulcer is successful, horses will begin to experience less and less pain. The ulcer will also begin to reduce in size. Generally, the rate in which the ulcer heals is relatively fast, at least initially. However, this rapid pace will often begin to wane after about one week, perhaps a few days sooner. A corneal ulcer, should, in the majority of cases heal or improve at a rate of about 0.6mm/day.
There are instances when a corneal ulcer will be resistance to treatment. Most likely, when it is, it is because complications have developed. Something may be lodged in the eye, the horse may have swiped the eye causing further damage, the eye may have become infected or the horse may have a compromised immune system. Not properly applying the medication prescribed by the vet can result in complications as well. The epithelium may also be abnormal. In this case, it may become necessary for the horse to undergo a keratectomy.
Treatment
Platelet Rich Plasma (PRP) has proven to be effective for the treatment of soft tissue injuries and conditions in human beings. Its tremendous success has encouraged those in veterinary medicine to use it to treat animals. For many conditions, it has proven equally effective. In addition to helping to expedite the healing of animals with soft tissue injuries, it has also proven to be a successful treatment for bone injuries corneal ulcers.
PRP therapy is especially effective for wounds or condition which occurs in those parts of the body that don’t receive a lot of blood flow. The cornea qualifies because it has few blood vessels.
Platelets are the “superstars” in PRP therapy. They contain growth factors which help with wound healing, blood clotting and tissue repair. Growth factors are like gold, they are extremely valuable. One of the best things about the therapy is that everything needed to produce it, can be found in the horse’s own body.
To retrieve valuable platelets, a veterinarian will draw a small amount of the horse’s blood. It is placed in a centrifuge, where it is spun. Spinning helps to separate all of the blood’s components. The platelets are removed and then injected into the site of the injury. Perhaps just as important as what is contained in the platelets (growth factors and other proteins) is what isn’t contained. There are no white blood cells. This is important because they can cause an inflammatory response and also the production of “degrading enzymes.”
PRP gel may be used instead of an injection. This might be more appropriate for eye injuries because of the pain and discomfort an injection might cause. There may also be fewer potential side effects or complications because no injection is being made. PRP gel includes growth factors, a high concentration of platelets, fibrin matrix, phagocytic and WBC cells. It works much like autologous blood therapy, which utilizes whole blood. PRP gel helps to both jumpstart and accelerate the healing process. It also helps reduce inflammation and has antimicrobial properties.
There are potential side effects associated with PRP therapy use, though they are minimal and considered far less serious than other forms of treatment. The primary side effects or complications have to with the injection site. There is some risk, albeit a small one, that a secondary infection may develop or that there will be an inflammatory reaction. This risk exists, anytime a horse receives a shot or injection of any kind. There aren’t typically any complications from the blood platelets injected into the horse, because everything is natural and comes from the horse’s body.
PRP therapy generally occurs in a veterinarian’s office. 52 mLs of blood is drawn and mixed with 8 mLs of anticoagulants. It is then injected into the site of the injury. A horse may be given a sedative so that they are more comfortable during the procedure. Ultrasound guidance is not typically needed. For the treatment of a corneal ulcer, PRP gel is likely to be used and rubbed directly on the eye. The amount will depend on the severity of the ulcer and the discretion of the veterinarian.
After the horse has received PRP therapy, the eye will need to be covered and they will need to rest. Strenuous physical exertion can cause complications, for instance, intra-ocular hemorrhage. The veterinarian will instruct the horse’s owner regarding after-care.
Corneal ulcers are generally treated with a combination of drugs, including antibiotics, atropine and anti-inflammatory medications. These are sometimes effective and other times they are not. PRP therapy helps to speed up the process and for this reason may be used in conjunction with the above, however, not in lieu of them.
