Research: Are Blue-Eyed Horses More Prone to Eye Disease?

Credit: Thinkstock Researchers showed that horses with blue eyes were more likely to have squamous cell carcinoma than horses with brown eye color. undefined

How often have you heard horse owners and veterinarians state that horses with eye colors other than the “normal” brown are more prone to eye disease? Researchers from the University of Illinois and the University of Georgia reviewed eye cases at the two medical centers. The results showed that while iris color didn’t matter in some problems, horses with blue eyes were more likely to have squamous cell carcinoma than horses with brown eye color.

The article published in Equine Veterinary Education was entitled “Prevalence of ophthalmic disease in blue-eyed horses,” and the complete article can be found on


“A perception exists amongst referring veterinarians and the lay public that blue-eyed horses have increased frequency of ocular disease. The aim of this retrospective study was to assess the prevalence of ocular disease in horses with blue or heterochromic eyes relative to those with brown eyes. The medical records of horses presenting to either the Comparative Ophthalmology services or Equine Medicine/Surgery services at 2 institutions were reviewed. Signalment, ocular and nonocular diagnoses were recorded. Ocular disease was divided into 4 categories: adnexa, cornea, intraocular/orbit and squamous cell carcinoma (SCC). Owners were contacted by telephone to confirm iris colour. Chi-square analysis was used to compare group proportions. A total of 164 eyes of horses with ocular disease and 212 eyes of horses without ocular disease were included. Blue eyes were equally common in the ocular disease and nonocular disease groups (P = 0.265). There was no significant difference in the proportion of blue- and brown-eyed horses when comparing the adnexal and corneal (P = 0.548), corneal and intraocular/orbit (P = 0.379) and adnexal and intraocular/orbit (P = 0.843) categories. A significant difference was detected in the proportion of blue-eyed horses between the adnexal (P = 0.000), corneal (P = 0.033), intraocular/orbital (P = 0.000) and SCC categories, with a higher proportion of blue-eyed horses in the SCC than in the other 3 groups. Horses with blue or heterochromic irides are more likely to develop ocular SCC than horses with brown irides, but are not more likely to have adnexal, corneal or intraocular/orbital disease or to be presented for evaluation of ophthalmic disease. Veterinarians should consider the results of this study when answering questions from the lay public regarding the predisposition of blue-eyed horses to ocular disease.”


Researchers for this study from the Department of Veterinary Clinical Medicine, University of Illinois Urbana-Champaign, were: B. E. Bergstrom, A. L. Labelle, M. E. Pryde, and R. E. Hamor. The researcher from the Department of Small Animal Medicine and Surgery, University of Georgia, was K. E. Myrna.

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