Equine Eye Vets Veterinary Eye Care for Horses in Texas
Inflammation of the cornea caused by fungal infections (fungal keratitis or FK) is more commonly seen in horses than any other domestic animal. The incidence, types of fungal infection, and clinical presentation varies depending on location in the country (or world).
Typically we assume that for a fungal infection to occur in the cornea the fungus needs to gain access to the deeper layers of the cornea after damage occurs to the outer corneal epithelial layer. Most fungal infections then result from some trauma to the corneal surface. There is some evidence that fungal organisms can gain access to structures inside the eye – possibly via the bloodstream.
Fungal ulcers or infections may present in various ways. Usually the affected eye will show:
· Pain – associated with damage to the corneal surface if a corneal ulcer develops
· Redness around the conjunctiva
· Hazy appearance (fluid or edema in the cornea) around the area of ulceration or infection
· Occasionally fine white deposits near the corneal surface
· Deep white, beige or yellow areas in the cornea – sometimes near the edge of the cornea
· Inflammation inside the eye (small pupil, hazy appearance to the eye)
In some cases there is a history of an injury to the cornea which appeared to heal initially (possibly with antibiotic use) and later the eye became painful and a light colored area develops in the cornea. Other cases may be associated with other diseases or therapies – horses with equine recurrent uveitis which are treated with corticosteroids seem quite predisposed to develop fungal infections.
Early diagnosis is very important if the disease is to be treated effectively. Fungal infections involving the corneal surface layers are approached is the same way as any corneal ulcer – cultures are taken from the affected area and scrapings into the corneal tissue are used to look for signs of fungal infection with a microscope. In some cases we will recommend submission of samples to laboratories for culture and identification of the type of fungus present.
In some cases the lesions seen are deep in the corneal tissue and involve the most posterior layers of the cornea. In these cases it is difficult to confirm the diagnosis of a suspected corneal infection without cutting through the more superficial layers – trauma which we would prefer avoid. In these instances the diagnosis is definitively made on the clinical appearance and the response to medical therapy. In some cases the diagnosis is confirmed as part of the surgical treatment.
Treatment of fungal disease has to be vigorous. Some corneal fungal infections may respond poorly to any therapy and the prognosis with fungal disease is always guarded. Treatment is either medical alone or medical and surgical. Various antifungal drugs exist and we have used several of these over the last twenty years. Medical treatment is usually administered via subpalpebral lavage for which we usually hospitalize the horse. The medications often need to be given for several weeks and even after the horse returns home the owner will need to continue some medication for a period of time.
In some cases the best approach to treating fungal keratitis is surgically. In these situations the affected area of cornea is excised and replaced with either donor tissue or graft material from the adjacent normal part of the eye. In some cases synthetic grafts may be needed to fill a defect after surgery.
With vigorous medical and surgical therapy there is a good chance to cure the disease and maintain vision provided no other ocular conditions (for instance equine recurrent uveitis) are present.