Introduction
It’s common for a dog’s eye color to change as they age. This is usually a normal process, especially in dogs with light colored eyes. The iris, which is the colored part of the eye, contains pigment which gives the eye its color. Over time, this pigment can fade or deplete, causing the eye to gradually turn a lighter shade. While this is normal, there are some instances where changing eye color can signal an underlying medical issue. Keep reading to learn about the common reasons for changing eye color in dogs and when you may need to seek veterinary care.
Quick Answers
– Aging and depleting pigment is the most common reason for lightening eye color in dogs.
– Certain dog breeds with light eyes like Siberian Huskies are predisposed to changing eye color as they age.
– Nuclear sclerosis, which is hardening of the lens, can also cause the eyes to take on a cloudy, bluish-gray appearance.
– Inflammation, infection, glaucoma, and cataracts are medical issues that may result in color change.
– If the color change happens rapidly or only affects one eye, it warrants a veterinary exam.
Gradual Lightening with Age
The most common reason for a dog’s eye color to turn lighter as they age is normal pigment fading. The iris contains melanin, which is the pigment that gives color to the skin, hair, and eyes. Over time, this pigment can naturally deplete and cause the eyes to lighten:
– Puppy eyes may start out very dark, then lighten to a lighter brown or hazel as an adult.
– Dogs with bright blue eyes as puppies may progress to a pale gray, greenish-yellow, or amber shade by the time they are seniors.
– Dark brown eyes may fade to a rich golden or yellowish tone with age.
This gradual, uniform lightening of eye color affects both eyes at a similar rate. It is a normal part of aging and not a source of concern. However, accelerated or uneven changes between the eyes could signal a medical problem.
Breed Predispositions
Some breeds are predisposed to changing eye color as they mature due to their genetics. The most well-known is the Siberian Husky. Huskies often start with dark blue or blue-green eyes as puppies. As adults, they progress to lighter shades of amber, brown, or green. These breed-specific changes usually affect both eyes evenly.
Other common breeds with lightening eye color include:
– Shetland Sheepdogs
– Border Collies
– Australian Shepherds
– Dachshunds
– Great Danes
– Weimaraners
Again, these gradual changes over years are expected in these breeds and are not a medical concern as long as they occur evenly in both eyes.
Nuclear Sclerosis
Nuclear sclerosis is a condition where the nucleus or center of the eye’s lens becomes hardened or cloudy. The lens sits behind the colored iris, so nuclear sclerosis can obstruct the normal eye color. This gives the eye a hazy, bluish-gray appearance sometimes described as an “oil slick.”
Nuclear sclerosis is associated with aging and is common in older dogs. It usually develops gradually in both eyes at the same rate. In early stages, nuclear sclerosis does not affect vision or require treatment. In advanced cases, dogs may have trouble seeing in dim lighting or at night. A veterinary ophthalmologist can evaluate and monitor the condition.
Inflammation
Inflammation of structures in the front of the eye can potentially cause changes in eye color. Two common examples include:
– Conjunctivitis – Inflammation of the conjunctiva or pink tissues surrounding the eye. This is often called “pink eye.”
– Uveitis – Inflammation of the uvea, including the iris. This is often related to autoimmune disease.
Both conditions can cause redness and swelling. With uveitis, inflammation of the iris specifically can deplete pigment. This may permanently lighten the eye color following repeated episodes. These conditions usually cause additional symptoms like eye discharge, squinting, or pain. Veterinary treatment is required.
Infections
Contagious infections that affect the eye can also result in color change in some cases. Common examples include:
– Canine herpesvirus – Herpes infections have been associated with blue eyes developing a yellow, rusty appearance.
– Lyme disease – Tick-borne illness that can cause uveitis and lightening of the iris.
– Leptospirosis – Bacterial infection that can involve uveitis.
– Blastomycosis – Systemic fungal infection where eye abnormalities occur in up to 25% of dogs.
Any eye infection warrants veterinary care. Topical and systemic medications will be prescribed. Prompt treatment can minimize permanent damage including altered eye color.
Glaucoma
Glaucoma refers to increased pressure within the eye. It is a painful condition and the most common cause of irreversible blindness in dogs. Glaucoma can result in changes to the appearance of the iris and pupil:
– The affected eye may take on a cloudy, bluish hue.
– The pupil may become dilated and fixed.
– The cornea may also appear hazy.
Glaucoma requires immediate emergency veterinary treatment to control eye pressure and save vision. Lifelong medication and monitoring is required once this condition develops.
Cataracts
A cataract describes opacity or cloudiness developing in the lens inside the eye. As cataracts progress, they obstruct the natural eye color. Affected eyes take on a cloudy, bluish-gray tone which obscures the iris. Mature cataracts can even turn the eyes a white or pale blue shade.
Cataracts are associated with aging, diabetes, genetics, and eye injury. Small incipient cataracts may not impair vision. More advanced cataracts do interfere with sight. Surgery to remove cataracts may be an option. Veterinary ophthalmologists can evaluate and monitor cataract progression.
Aniridia
Aniridia is the complete or partial absence of the iris, which is very rare in dogs. This can occur as a congenital defect present from birth. Some cases are progressive and develop with chronic eye diseases like glaucoma.
Aniridia results in a lack of visible iris pigment and very light colored eyes. However, vision is not necessarily impaired unless related eye diseases are present. Examination by a veterinary ophthalmologist is recommended.
Progressive Retinal Atrophy (PRA)
PRA describes a group of inherited, degenerative eye diseases affecting the retina. While PRA does not directly affect iris pigment, some forms like PRA-prcd eventually progress to complete retinal detachment. This gives the eyes an almost white appearance with no visible retinal blood vessels.
However, PRA is diagnosed well before this based on eye exams and DNA testing. Atrophy of the retina leads to progressive vision loss. There is no cure, but dogs can often adjust well to declining sight over time.
When to See the Veterinarian
Schedule an appointment with your veterinarian if your dog’s eye color seems to change rapidly or unevenly. You should also seek veterinary care if your dog shows any of these signs:
– The color change affects only one eye
– Your dog is squinting, pawing at the eye, or seems to be in eye pain
– You notice discharge, crustiness, or excessive tearing
– Your dog seems to be having vision problems
Your vet will perform a thorough eye exam and evaluate your dog for underlying issues. In some cases, referral to a veterinary ophthalmologist for specialized testing may be recommended. Addressing the cause of color change could help prevent permanent alteration of the eye.
Conclusion
In summary, dogs may naturally experience lightening of their eye color as they age. Gradual depletion of eye pigment affects both eyes evenly and is not a major concern in most cases. However, if your dog shows accelerated, uneven, or sudden color changes, see your veterinarian right away. This could signal inflammation, glaucoma, infection, or other problems requiring treatment. With prompt care, it may be possible to restore or preserve normal eye color and vision. Overall, monitoring for abnormal eye or vision changes is part of providing good care for your senior dog.
References
[1] Maggs DJ, Miller PE, Ofri R, Slatter’s Fundamentals of Veterinary Ophthalmology, 6th Edition, Elsevier Health Sciences, 2018.
[2] Gelatt KN and Gelatt JP, Veterinary Ophthalmic Surgery, 1st Edition, Elsevier Health Sciences, 2010.
[3] American College of Veterinary Ophthalmologists, Nuclear Sclerosis in Dogs, https://www.acvo.org/new/diplomates/resources/acvo-blue-book/12-ophthalmic-diseases/cornea-and-sclera/387-nuclear-sclerosis-in-dogs.html
[4] Magrane W. Canine Conjunctivitis. American College of Veterinary Ophthalmologists. https://www.acvo.org/new/diplomates/resources/ACVOBlueBook/12-OphthalmicDiseases/Eyelids/CanineConjunctivitis.pdf
[5] American College of Veterinary Ophthalmologists. Uveitis. https://www.acvo.org/new/diplomates/resources/ACVOBlueBook/12-OphthalmicDiseases/Uvea/Uveitis.pdf
[6] American College of Veterinary Ophthalmologists, Glaucoma – Canine, https://www.acvo.org/new/diplomates/resources/ACVOBlueBook/25-Glaucoma/Glaucoma-Canine.pdf
[7] American College of Veterinary Ophthalmologists. Progressive Retinal Atrophy (PRA) in Dogs. https://www.acvo.org/new/diplomates/resources/ACVOBlueBook/17-HereditaryEyeDiseases/ProgressiveRetinalAtrophyDogs.pdf
