Q:I was wondering about corneal ulcers. I have a 30-year-old horse that has lost eyesight in one eye from age, and I am treating him now for a corneal ulcer. I read your article on eye problems (November 2010 issue) and was wondering what medications are usually used for treating this problem. I know I am using (antibiotics) neomycin and polymyxin B and bacitracin, zinc ointment, and atropine sulfate. He is doing great, but I rarely read much about treatment for this problem.

Lucy Smith, via e-mail

A: Once a corneal ulcer is diagnosed, the therapy must be carefully considered to ensure comprehensive treatment. Medical therapy almost always comprises the initial major thrust in ulcer control, albeit tempered by judicious use of adjunctive surgical procedures. This intensive pharmacological attack should be modified according to its efficacy. Subpalpebral (beneath the eyelid) or nasolacrimal (tear drainage) lavage treatment systems can be employed to treat a fractious horse or one with a painful eye that needs frequent therapy. The clarity of the cornea, the depth and size of the ulcer, the degree of corneal vascularization (blood supply), the amount of tearing, the pupil size, and the intensity of the anterior uveitis (inflammation of the iris and ciliary body, which is a muscular ring located in the front part of the eye) should be monitored. Serial fluorescein dye staining of the ulcer is indicated to assess healing. Self-trauma should be reduced with hard or soft cup hoods (that protect the eye).

Bacterial and fungal growth must be halted and the microbes rendered nonviable. Broad-spectrum topical antibiotics are usually administered with culture and sensitivity tests aiding selection. Topically applied antibiotics, such as chloramphenicol, bacitracin-neomycin-polymyxin B, gentamicin, ciprofloxacin, cefazolin, or tobramycin ophthalmic solutions, may be used to treat bacterial ulcers. Voriconazole, miconazole, and natamycin are often used for topical treatment of fungal ulcers