Ophthalmology Patients Offered New Treatment
Carmen M.H. Colitz, DVM, PhD
Assistant Professor of Veterinary Ophthalmology
Diplomate, American College of Veterinary Ophthalmologists

Equine Recurrent Uveitis (ERU), also called Moonblindness, is the number one cause of blindness in horses worldwide.  There is an 8% prevalence overall and a 25% prevalence in the Appaloosa breed.  Clinical signs include epiphora (tearing), corneal edema (cloudiness), aqueous flare, cataract, peripapillary chorioretinal scarring (butterfly lesions) and retinal detachment.  End stage cases will have phthisis bulbi (shrunken eye) and become blind.  The owner usually notices epiphora, corneal edema and variable blindness when the disease is active.  These clinical signs recur every few weeks to months and then signs dissipate over the next one to two weeks.  If not aggressively treated with appropriate medications, horses will gradually lose vision due to cataract, chorioretinal scarring and/or retinal detachment.  Even horses that are treated appropriately can eventually lose vision.  Horses can be affected unilaterally or bilaterally.
Unfortunately, most horses present to the veterinary ophthalmologist after a long history of recurrent flare-ups and most of the damage has occurred.

The initial cause of ERU is often not identifiable when the horse is examined.  ERU is an immune-mediated disease wherein the T cells are activated when they “see” an antigen that resembles the initial cause.  Therapy for ERU has traditionally been topical corticosteroids and atropine, and oral non-steriodal anti-inflammatory agents such as Banamine.

Cyclosporine, a T cell inhibitor, is the ideal treatment for ERU, but when used topically, it cannot penetrate the cornea and thus cannot treat the uveitis.  Systemic cyclosporine in a horse becomes expensive and can cause immunosuppression.

Drs. Brian Gilger and Janice Allen at North Carolina State University College of Veterinary Medicine have developed a cyclosporine implant that is surgically sutured into the anterior vitreous of eyes with ERU and results have been favorable.  Many horses are able to retain vision with no need for treatment.  The implants are made to last between two and four years.
Veterinary ophthalmologists at LSU can examine horses with ERU, and if they fit the criteria, can refer horses to NCSU to have the implants surgically inserted.  Criteria include rapid response to appropriate therapy, no cataract formation and no fundic changes.  These horses are ideal because they have not yet lost vision from ERU.