A two-year-old colt developed a small white spot in the middle of his left eye in mid spring, which spread within a few days into a narrow band down the middle of the eye. It was believed to be due to an injury, but the eye didn’t appear painful or sensitive to light.
The colt was started on a triple-antibiotic eye ointment with no improvement. In fact, the band spread toward the back of the eye and became denser and raised. No ingrowth of blood vessels was seen, as often occurs in bad bacterial or fungal ulcers. In fact, fluorescein staining of the eye showed no corneal breaks.
The original spot, which looked like a superficial ulcer, was now a small raised bump, but the pupil remained reactive.
Treatment was switched to a gentamicin spray, but the band continued to widen. The colt was stall-confined because the opacity was interfering with his vision.
After another two weeks, a new similar white spot appeared toward the front of the eye.
Dr. Jill Beech at New Bolton Center reported similar problems in a few horses in recent years, but the cause was unknown and no treatment had been successful. A few horses had cleared spontaneously after six months, she said, but the fate of the others was unknown.
At this point a virus was suspected, especially since viral cornea infections in people and other animals are typically painless. The colt was put on an Acyclovir cream, an antiviral medication. No effect. The new spot of corneal opacity in the front of the eye continued to deepen and widen.
The colt was put on a combination of echinacea, lysine, zinc and vitamin C for nutritional support of his immune system in response to a viral infection and MSM in hopes of quieting inflammatory and autoimmune responses. This combination stopped the spread and, in two weeks, it began to decrease in size.
Oddly, on the same side as the eye problem, the colt developed tiny warts inside his nose, precisely on the pathway of the drainage of tears from his nasolacrimal duct. It was strongly suspected the two were related. Warts are caused by the equine papilloma virus. Although papilloma virus involvement of the cornea has never been documented in a horse, it has in people and other animals.
Since tetracyclines are used to treat autoimmune reactions involved with chronic Lyme and rheumatoid arthritis, the colt was started on intravenous tetracycline. The eye began to clear and, oddly enough, the warts also began to regress.
After 2.5 weeks, the tetracycline was stopped and all that remained was a narrow central band. The colt continued on the immune-stimulating supplements for three weeks, and the eye continued to clear. In four months, the eye was nearly normal.
Why the warts regressed at all with tetracycline is a mystery. However, it seems there was a connection between them and the eye virus.