Dear Dr. T.,
“I’ve noticed lately that my dog’s eyes are cloudy. He’s 11 years old and seems very healthy but I’m worried he’s getting cataracts. Is my dog going to go blind?”
Gazing into your dog’s eyes increases oxytocin levels for both you and your dog (3). If you practice mutual eye-gazing regularly, as I do with my dogs, I can understand how a cloudy eye could be worrisome!
The most common causes of cloudy eyes in dogs are normal aging changes to the lens, corneal disease, dry eye, glaucoma, cataracts and uveitis. Some of these eye conditions are not a big deal but others cause pain, blindness and can be a sign of a bigger problem.
It’s pretty difficult to tell exactly what’s going on when you’re looking at the eyes at home. That’s why it’s really important to have your veterinarian check your dog’s cloudy eyes.
Causes of Cloudy Eyes in Dogs
|Glaucoma||Late stage causes blindness||Yes|
|Dry Eye||Late stage affects vision||Somewhat|
|Cataracts||Yes||Late stage is painful|
Nuclear Sclerosis of the Lens
Nuclear sclerosis is the most common thing I find when clients say their dog’s eyes are cloudy. Also called lenticular sclerosis, it’s a normal aging change caused when the normal proliferation of lens fibers compress the lens’s central nucleus. Fortunately, it doesn’t cause significant vision loss.
According to a study done in 2004, 50% of dogs over age 9 years have eye lenses affected by nuclear sclerosis (5).
Your veterinarian should be able to diagnose nuclear sclerosis with a simple exam with an ophthalmoscope. The good news is that no treatment is necessary for nuclear sclerosis!
The cornea is the clear front part of the eye. It needs to be perfectly clear so light can pass through to the retina. The inner layer of the cornea has to constantly pump water out of the cells to keep it clear. Anything that causes an imbalance in the cornea can overwhelm this pumping mechanism.
Things that can make the cornea appear cloudy include:
- Corneal Ulcer–trauma, stray hairs, and inherited corneal abnormalities lead to corneal ulceration when the surface of the cornea becomes eroded.
- Corneal Endothelial Dystrophy–also called corneal dystrophy, this issue affects the inner surface of the cornea. It can be a genetic eye condition or secondary to inflammation.
- Inflammation–infectious diseases from viruses, fungi and bacteria can affect the eye.
- Superficial Keratitis–inflammation of the outer cornea caused by chronic irritation. Entropion (inward curling of the eyelid) and dystichia (abnormal hairs on the eyelid) are common causes.
- Lipid Keratopathy–lipid (fat) deposits within the cornea that often appear as white spots or streaks.
In a normal dog’s eye, the liquid flows through a sort of filter from the front to the back of the eye. When the filter gets clogged, the liquid is trapped in the front of the eye and builds up pressure.
The abnormally high intraocular pressure increase causes significant pain (squinting), redness, cloudiness, and eventually blindness. The medical term for this eye problem is glaucoma.
Glaucoma can occur due to genetic reasons (primary glaucoma) or secondary to trauma, infection and cancer. Only one eye may be affected at the time of diagnosis, but in hereditary glaucoma, both eyes eventually show signs of the disease.
Glaucoma is diagnosed mainly by physical exam and testing for increased intraocular pressure. Treatment may involve multiple eye drops as well as oral medication.
This eye disease is an emergency situation. It is of utmost importance to quickly diagnose and treat glaucoma. Failure to do so will lead to blindness and undue discomfort for your dog.
The medical term for dry eye is keratoconjunctivitis sicca (KCS). The most common cause of the condition in dogs is autoimmune destruction of tear gland tissue. Many breeds are predisposed to developing KCS with the Cocker Spaniel, English Bulldog, Lhasa Apso and Shih Tzu being overrepresented.
Symptoms include eye redness, increased mucoid eye discharge, squinting and rubbing of the eye. Advanced KCS leads to poor corneal health and the appearance of a cloudy eye.
Your veterinarian can check your dog’s tear production by holding a small piece of absorbent paper under the eyelid. Under a certain number in a minute means tear production is abnormally low.
Treatment often requires several different eye drops to stop the autoimmune destruction of the tear glands as well as to keep the eye moist.
Uveitis is an eye disease caused by inflammation on the inside of a dog’s eye. This eye problem can occur in one or both eyes at the same time.
Tick-borne organisms (like Ehrlichia) and fungal, bacterial and viral infections can cause uveitis. External trauma to the eye as well as internal trauma from a diseased lens can also cause uveitis.
Physical signs of uveitis include squinting, redness, cloudiness, and a small pupil. Testing the eye for uveitis requires measuring intraocular pressure and checking for underlying infectious disease.
The key to resolving uveitis is to identify and treat any underlying disease. A steroid eye drop is used in many cases to decrease intraocular inflammation.
Complicated cases of uveitis may require referral to a veterinary ophthalmologist for the best outcome.
I’ve had so many people tell me their dogs have cataracts only to find out it was only the normal aging changes of lenticular sclerosis. Real cataracts happen when the lens, in the middle of the eye, becomes partly or fully opaque.
Small cataracts don’t affect a dog’s vision much but mature cataracts can cause complete blindness. And it’s usually not too difficult to diagnose a mature cataract because it makes the dog’s pupil look white.
The most common type of cataract in purebred dogs are hereditary in nature. Over 150 breeds are prone to hereditary cataract formation including the Bichon Frise, Boston Terrier, Miniature Poodle, Miniature Schnauzer, Shih Tzu and Yorkshire Terrier (1).
Diabetic cataracts are the second most common type of cataracts in dogs (4). Diabetic dogs form cataracts at a much higher rate than any other dogs because high blood sugar causes the eye lens to turn opaque.
One study found that 80% of diabetic dogs developed cataracts within 16 months of diagnosis (1). Diabetic dogs almost invariably have other symptoms, including excessive drinking and urination.
Dogs of any age can develop cataracts. Even very young dogs can be affected and we call this form juvenile cataracts. Boston Terriers and French Bulldogs are two breeds that are more likely to develop cataracts at a young age.
An older dog can form senile cataracts as a result of degenerative processes. And the older a dog gets, the more likely he is to develop cataracts. One study showed that about 50% of dogs over the age of 13.5 years had some degree of cataracts in their eyes (5). But many older dogs with cataracts still have a functional level of vision.
Cataracts can cause impaired vision, blindness and even severe pain if they eventually start to dissolve.
Veterinary ophthalmologists regularly perform cataract surgery to remove cataractous lenses. In 2021, the cost of cataract surgery in my large U.S. city was about $4500 for surgery on one eye and $5600 for both eyes.
The procedure has a high rate of success and can restore a dog’s eyesight. Removing the abnormal lens tissue can also prevent a dog from having long-term pain.
Cloudy eyes in dogs have many causes from totally benign to highly problematic and painful. If your dog’s eyes are cloudy, especially if they have any other symptoms, don’t wait to have your vet check him over. Many eye diseases can be treated and even cured if they’re caught in time.
You can ask your own question on our ASK A VET page!
- Beam, S., Correa, M. T., & Davidson, M. G. (1999). A retrospective cohort study on the development of cataracts in dogs with diabetes mellitus: 200 cases. Veterinary Ophthalmology, 2 (3), 169-172.
- Davidson, M. G., & Nelms, S. R. (2007). Diseases of the canine lens and cataract formation. Veterinary ophthalmology, 2, 859-87.
- Nagasawa, M., Mitsui, S., En, S., Ohtani, N., Ohta, M., Sakuma, Y., … & Kikusui, T. (2015). Oxytocin-gaze positive loop and the coevolution of human-dog bonds. Science, 348 (6232), 333-336.
- Salgado D, Reusch C, Spiess B: Diabetic cataracts: different incidence between dogs and cats. Schweiz Arch Tierheilkd 2000 Vol 142 (6) pp. 349-53.
- Williams, D. L., Heath, M. F., & Wallis, C. (2004). Prevalence of canine cataract: preliminary results of a cross-sectional study. Veterinary Ophthalmology, 7 (1), 29-35.