eye abnormalities in horses
It’s no secret that some horse breeds with limited gene pools are at risk of developing health issues associated with inbreeding. But researchers recently found that this isn’t the case when it comes to eye problems in a 400-year-old Czech breed: The Old Kladruber horse doesn’t seem to be at significant risk for hereditary ocular disease.

“I was relieved,” said Radka Andrysikova, PhD, MVDr, a past resident at the University of Zürich Vetsuisse Faculty, in Switzerland. “I had expected to find something—my guess was some type of cataract formation, probably related to some stallion lines—as a result of potential inbreeding, but none of my fears came true.”

In their recent study, Andrysikova and colleagues examined 261 Old Kladruber horses’ eyes. About half the horses were black, and the other half were gray—an important consideration given that coat color can affect ocular health, she noted. The horses ranged in age from three months to 27 years.

The research team identified ocular abnormalities, such as cataracts or iris hyperpigmentation, in 51% of the horses, she said—that’s significantly lower than what researchers have found in other breeds. Previous studies have reported such abnormalities in 76% of Lipizzaners, 68% of Thoroughbreds, and 90% of Exmoor ponies, she noted.

They did, however, find that normal, nondisease-causing ocular anatomy variations were more frequent in Old Kladrubers than in other breeds. For example, she found visible posterior suture lines (fibrous lines on the lens where the tissue came together during development) in 85% of the study horses, whereas this normal aged-related change was reported in only 7% of Exmoor ponies and less than 1% of Lipizzaners. However, it’s possible the other researchers simply didn’t look for “normal” ocular changes and centralized their work on truly problematic issues only, she said.

The Old Kladruber is a “highly conserved old breed” with a small population size numbering only about 1,500 horses worldwide, said Andrysikova. Previous studies have shown that, despite the small population, genetic variation is high and inbreeding rates are low—factors which might contribute to the breed’s generally good ocular health, she said.

“I dare say that Old Kladruber horses are likely to have robust ocular health as a breed, and no extra precautions need to be taken by breeders,” she said. “However, I would strongly encourage any prospective owner of one of these horses to get a standard prepurchase examination done because any horse could have experienced some kind of traumatic ocular event or suffered from equine recurrent uveitis or immune-mediated keratitis. That said, the Old Kladrubers that I examined do not seem to be prone to such chronic immune-mediated problems.”

The study, “Ocular abnormalities in a herd of Old Kladruber Horses: A cross‐sectional study,” was published in Veterinary Ophthalmology.