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“No one familiar with the Appaloosa breed would dispute that the breed is at increased risk for both uveitis and blindness.”

Blindness In Appaloosas

When we began pulling together the research for this site, one equine vet told us, “No one familiar with the Appaloosa breed would dispute that the breed is at increased risk for both uveitis and blindness.” And that is indeed the case. So many people in the horse world know of someone with a blind Appaloosa that few consider it an unusual fate for an Appy.

Despite the prevalence of blindness in the breed, studies on this subject remain limited. But veterinary researchers have clearly identified the existence and scope of the problem:

  • The first known study to identify a link between Appaloosas and uveitis was published in the journal Animal Genetics in 1988. Based on an analysis of 16,242 cases admitted to Cornell University’s College of Veterinary Medicine over a 12-year period, the study reported that “In the uveitis diagnosis category, Appaloosas had a significantly higher risk of developing uveitis relative to Thoroughbreds, while Standardbreds had a significantly lower risk of developing uveitis relative to Thoroughbreds.”

See an abstract of the study here.

  • A second study of 372 horses, focused on the relationship of the bacteria leptospirosis and uveitis, was published in the Journal of the American Veterinary Medical Association in 1995. This study also found a troubling breed proclivity: “Of the 112 horses with uveitis, 28 (25%) were Appaloosas, compared with only 10 of the 260 (4%) horses without uveitis (odds ratio, 8.3). In addition, 19 of the 28 (68%) Appaloosas with uveitis developed blindness, compared with only 30 of the 84 (36%) non-Appaloosas with uveitis that lost vision in 1 or both eyes (odds ratio, 3.8).”

In simple English, the odds ratio analysis means this: Appaloosas are eight times more likely to develop uveitis and four times more likely to go blind as a result.

See an abstract of the study here.

In Equine Ophthalmology, a comprehensive and definitive textbook published in 2005, the chapter on equine recurrent uveitis summarized that study this way:

“A field study of a large number of cases in New York confirmed the breed predilection and indicated that the odds of finding uveitis were 8.3 times greater in Appaloosas than in all other breeds combined.”

  • Finally, a third study reported in Equine Ophthalmology was based on the analysis of case records of 160 horses with uveitis. A full 25%, or 42, of these uveitis cases occurred in Appaloosas. (Source: Equine Ophthalmology, Chapter 7, page 307, ‘Equine Recurrent Uveitis in Appaloosa Horses.’)

This prior research has sparked new efforts to understand why Appaloosas are more likely to get uveitis than other breeds. Read about those studies here.