Hypnotic and haunting. Both are equally correct in describing dogs with heterochromia – a condition where their eyes are two different colors. And while this phenomenon may seem unique, it’s quite common among certain dog breeds. What, then, is heterochromia?
Heterochromia is caused by a lack of the pigment melanin in the iris (the colored part) of the eye. The iris in most dogs has high amounts of melanocytes that give it a more typical golden-brown to dark color. Dogs with blue eyes have a mutation in the genes responsible for regulating the concentration and distribution of melanin, resulting in the absence of melanocytes in the iris, thereby giving them their blue eyes. Coat color and pattern can also play a part -- merle, dapple and white coats as well as increased white patterns around a dog’s head.
Either hereditary (a dog was born with it) or acquired (the eye’s color changes over time as the result of an eye injury, illness or infection), heterochromia has three variations: complete (one eye is a different color than the other), sectoral (part of the iris is blue, the rest of it a different color), and central (different colors within the iris give it a spiked pattern).
Complete heterochromia in dogs is frequently seen in Australian cattle dogs, Australian shepherds, Dalmatians and Siberian huskies. Sectoral and central heterochromia are frequently seen in Border collies, Catahoula leopard dogs, Chihuahuas, Dachshunds, Dalmatians, Great Danes (harlequin coat patterned), Shetland sheepdogs and Shih tzus.
While it’s a common misconception that dogs with blue eyes suffer from vision problems, even blindness, those with hereditary heterochromia have normal vision. Another misconception is that they have hearing problems. While untrue in most cases, there are rare exceptions. Dalmatians with sectoral heterochromia have a higher incidence of partial or complete deafness.
On the other paw, as mentioned earlier, acquired heterochromia or a loss of pigmentation within the iris, can be attributed to many factors. Among them are an injury to the eye, various health conditions and even some medications.
Should YOU notice a change in the color of your own heterochromatic dog’s eyes or if they appear uncomfortable or painful, bring him to the vet immediately for a thorough eye examination. Why? Because the reasons for this change, unrelated to his heterochromia, can include cataracts, corneal dystrophy, diabetes, eye tumors, glaucoma, iris ectropion, melanoma of the eye, microphthalmia, nuclear sclerosis, ocular disease, optic nerve hypoplasia, retinal dysplasia and uveitis.
Article by Nomi Berger. Nomi is the bestselling author of seven novels, one work of non-fiction, two volumes of poetry, and hundreds of articles. She lives in Toronto, Ontario, Canada with her adopted Maltese, Mini, and has been writing as a volunteer for animal rescue groups in Canada and the U.S.A. since 2013.