Equine Eye Problems Discussed by Veterinarians

Ophthalmology in horses was declared such an important topic at the 2009 American Association of Equine Practitioners (AAEP) Convention in early December that two Table Topics were held. In one session approximately 175 veterinarians attended, and in the second session about 120 practitioners were in attendance.

The discussion in the first Ophthalmology Table Topic started with a review from Ann Dwyer, DVM, on the AAEP-sponsored Focus on Ophthalmology Meeting that was held in Raleigh, N.C., in October 2009. Dwyer reported the attendance for the Focus meeting was excellent, and the veterinarians attending the meeting found the conference to be very helpful in improving their abilities to diagnosis and treat equine ophthalmic disease.

Amber Labelle, DVM, then gave a brief overview of the suspected causes and mechanisms of equine recurrent uveitis (ERU or moon blindness), including a novel surgical therapy using suprachoroidal cyclosporine A implants.

Dwyer and Labelle agreed ERU is a very frustrating disease to treat. While progress has been made in treatment options and understanding of the pathophysiology and various risk factors of the syndrome, ERU is still a major cause of blindness in horses. Both veterinarians repeatedly emphasized the need for routine eye exams, especially as part of annual or bi-annual wellness exams, careful documentation of all findings, and aggressive therapy for intraocular inflammation.

The conversation then turned to ocular exam findings during pre-purchase examination. The facilitators polled the attendees about the incidence of several findings of uncertain significance, such as single corneal stria (narrow, band-like structure) and focal regions of chorioretinal (a layer in the eye between the retina and sclera that furnishes the blood supply) pigment alteration.

Dwyer and Labelle encouraged all attendees to make dilation of the pupils part of their routine pre-purchase exam, as this allows detection of small and subtle lesions, particularly of the lens, that might be otherwise overlooked.

Prepurchase report protocols and tips on digital photography of the anterior segment of the eye were also covered.

The discussion then turned to cancerous lesions around the eye, and the facilitators gave an update of various medical and surgical methods of treatment. While many cases respond well to early intervention, removal of the eye is sometimes the most appropriate treatment for advanced cancerous lesions. Standing enucleation (removing the eye in a heavily sedated horse using administration of local anesthetics to numb the entire surgical area) was covered, as this technique is being used by more and more veterinarians to decrease the need for general anesthesia. All the veterinarians attending agreed that small lesions are easier to treat than larger lesions, and that early detection is very important in obtaining a successful outcome.

In the second Ophthalmology Table Topic at AAEP Carol Clark, DVM, Dipl. ACVIM, and Labelle facilitated discussion. The Table Topic started with an overview about the possible causes of ERU and continued with the possible role of Leptospira bacteria in the pathogenesis of ERU. Different antibiotic therapy strategies as well as topical and systemic medical treatments were covered. Labelle again discussed the use of suprachoroidal cyclosporine A implants to control or decrease future outbreaks of ERU.

The different clinical appearances of ERU in North America versus Northern Europe was also reviewed. Again the need for early detection of the disease and the importance of regular eye examinations for all horses was emphasized.

The remainder of the session focused on different kinds of corneal disease, primarily corneal ulcers and stromal abscesses. The different classes of topical antibiotics and antifungals were briefly reviewed, and recommendations for treating both simple and complicated corneal ulcers were made.

Stromal abscesses, a particularly frustrating form of corneal disease, was also addressed. Clark explained the value of culture and cytologic examination of cells from the surface of the eye in making the correct diagnosis and implementing the most appropriate treatment early in the course of the disease.

These Table Topics were facilitated by Ann Dwyer, DVM, Carol Clark, DVM, Dipl. ACVIM, and Amber Labelle, DVM, who wrote this report.

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