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.