Moonblindness

Jim Hamilton, DVM

The cause of "moonblindness" or "periodic opthalmia" is not known. Several etiologic agents are known to cause symptoms to appear - they include Leptospira spp., onchocerciasis, parainfluenza 3 virus and equine influenza virus. It appears that one or more of the above pathogens "sensitizes" the eyes but may not be required for recurrent attacks. I am not aware of any true genetic predisposition to this disease, however, the Appaloosa breed has an ocular syndrome with similar symptoms.

The common symptoms of moonblindness include conjunctivitis (red eye), increased lacrimation (tearing) and blepharospasm (half-closed, painful eye) and each episode lasts 1-2 weeks. There are also significant changes to the back part of the eye, posterior uveitis, which can ultimately lead to blindness. Treatment includes anti-inflammatories (Banamine granules) and topical steroid/antibiotic opthalmic ointment for a week to ten days.

If it is not diagnosed early, topical atropin may be needed as well. The unfortunate reality is that the condition is not thought to be curable - you win the battles but the war remains. Once that expectation is removed, one need only remember one rule: recognize it early and treat it aggressively and you'll have more good days than bad.

e-mail Dr. Jim Hamilton, DVM
Southern Pines Equine Associates