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