Are Blue-Eyed Horses More Prone to Eye Disease?

Are Blue-Eyed Horses More Prone to Eye Disease?

Labelle said horses with pink eyelid skin are more likely to develop SCC than those with black eyelid skin.

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New evidence from a study suggests that while owners of blue-eyed horses and those with a mixture of blue and brown (heterochromic) eyes might need to take special care to prevent their horses from developing squamous cell carcinoma (SCC), those horses are not more at risk for general vision or eye problems than their brown-eyed counterparts.

Amber Labelle, DVM, MS, Dipl. ACVO, assistant professor and veterinary ophthalmologist at the University of Illinois Veterinary Teaching Hospital, and colleagues retrospectively studied the medical records of 164 horses with ocular disease and 212 horses without eye disease in order to determine if horses with blue or heterochromic eyes were more prone to eye problems, as previously thought by many veterinarians and horse owners.

The team found that blue and heterochromic eyes were just as common as brown eyes in both groups of horses. The researchers found no significant difference between the proportion of blue- and brown-eyed horses with problems in adjacent structures to the eye (such as eyelid lacerations and neoplasia), corneal disease (such as ulcerative and non-ulcerative keratitis), or disease in the eye or eye socket (including equine recurrent uveitis, glaucoma, cataract, intraocular neoplasia, orbital cellulitis, and orbital neoplasia).

“The most important takeaway from this study is that blue-eyed horses are not any more likely to get disease of the eyeball itself than brown-eyed horses,” said Labelle. “There is a common misconception that the blue color of their iris makes them more likely to get cataracts, have vision problems, or develop equine recurrent uveitis; this study demonstrates that this isn't true.”

However, the team found that significantly more blue-eyed and heterochromatic horses had SCC (the most common tumor of the eye and adjacent structures, such as the third eyelid, the edge of the cornea, and the main eyelid), compared to brown-eyed horses.

Labelle said that skin pigmentation around the eye factors in to the development of SCC: “Blue-eyed horses are more likely to have pink eyelid skin rather than black eyelid skin. Pink skin has less pigment in it and is more likely to develop the skin cancer squamous cell carcinoma.”

At-risk horses include some draft breeds; horses with areas of unpigmented skin; and light-colored horses, such as cremellos and some Appaloosas, Paints, and Quarter Horses. In addition, horses living in places with stronger ultraviolet (UV) intensity, such as in higher altitudes and those closer to the equator, are also more at risk.

To help prevent SCC, Labelle recommends owners of at-risk horses use fly masks to help block UV rays, provide shade in turnout areas, and avoid turnout during hours when UV rays are the most intense. In addition, veterinarians should keep an eye on all horses, and especially those with blue eyes, for the development of small and early-stage lesions, which could develop into SCC.

The study, "Prevalence of ophthalmic disease in blue-eyed horses," was published in Equine Veterinary Education

About the Author

Sarah Evers Conrad

Sarah Evers Conrad has a bachelor’s of arts in journalism and equine science from Western Kentucky University. As a lifelong horse lover and equestrian, Conrad started her career at The Horse: Your Guide to Equine Health Care magazine. She has also worked for the United States Equestrian Federation as the managing editor of Equestrian magazine and director of e-communications and served as content manager/travel writer for a Caribbean travel agency. When she isn’t freelancing, Conrad spends her free time enjoying her family, reading, practicing photography, traveling, crocheting, and being around animals in her Lexington, Kentucky, home.

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