Cataracts are a vision issue caused by clouding of the lens within the eye and are a common problem in humans as well as dogs. Although most often developing in middle-aged or senior dogs, cataracts can also occur in puppies. Cataracts are not painful, but they can lead to significant vision loss. Often, the only noticeable symptom is a cloudiness in your dog's eyes, although if vision loss is severe, your dog might bump into furniture or show other signs of not seeing well.
In dogs, cataracts are most often a hereditary problem and certain breeds, including Cocker spaniels, poodles, Boston terriers, and Labrador retrievers, are more prone to this disorder, although any dog potentially can develop them. Treatment options are limited but effective, and some disease management may also be available depending on the type of cataract that is present.
What Are Cataracts?
The eyeball is a complex structure with several parts. Positioned behind the cornea (the clear covering over the front of the eye) and colored iris is a thick, clear lens made of protein and water. The lens reflects light onto the retina (the light-sensitive cells at the back of the eyeball), which transmits the sensory information to the brain, creating vision. Dogs, cats, and many other mammals also have a layer of cells called the tapetum lucidum behind the retina which further helps reflect light.
If the lens becomes damaged or unable to properly reflect light, vision loss occurs. Cataracts are changes in the lens of the eye that cause it to become cloudy or milky in appearance. This cloudiness blocks the light from adequately entering the eye and therefore negatively affects a dog's sight. Cataracts are defined by how much of the lens they are blocking and typically progress through four stages over time.
- Incipient cataracts: This early stage of cataract covers less than 15 percent of the lens.
- Immature cataracts: These cataracts can cover 15 to 100 percent of the lens, but a reflection from the tapetum lucidum is still present to allow some light to reflect onto the retina.
- Mature cataracts: Also known as fully developed cataracts, mature cataracts cover 100 percent of the lens and no reflection from the tapetum lucidum is present.
- Hypermature cataracts: In this stage, the cataract covers 100 percent of the lens and the lens has become wrinkled and slightly solidified. There is no reflection from the tapetum lucidum.
Cataracts usually become more mature over time, but in some young dogs, they can regress and disappear. Cataracts can occur in just one eye, but most often develop in both.
Symptoms of Cataracts in Dogs
Often, your only indication that your dog has cataracts is a cloudy or milky appearance to the eyes when your dog looks at you in bright light. As dogs depend heavily on their sense of smell, they can often compensate for slight vision loss in the early stages of cataract development.
If cataracts progress to cover the entire lens, you might start to see signs of clumsiness in your dog due to vision loss. Bumping into furniture, missing tossed toys or treats, and hesitancy to jump onto the couch or walk down stairs are typical. Some dogs might become anxious or clingy.
Causes of Cataracts
Some dogs are born with cataracts, but most dogs develop them as adults. There are a variety of reasons why cataracts can form. Some of these causes include:
- Genetics: The most common cause of cataracts in dogs is genetics. These cataracts are referred to as inherited cataracts even though they may not show up until a dog is an adult.
- Diabetes mellitus: Diabetes is the second most common reason why a dog develops cataracts and the most common cause of canine blindness. Up to 75 percent of diabetic dogs will develop cataracts, and of those dogs, three-quarters will become blind within a year if the diabetes is not treated.
- Trauma: Severe damage to the lens of the eye can result in the formation of a cataract.
- Retinal disease: While not common, late-stage retinal degeneration can cause cataracts in dogs.
- Uveitis: If a dog has inflammation inside its eye, called uveitis, cataracts may result.
- Age: With age comes age-related changes that can contribute to cataract formation.
Diagnosing Cataracts in Dogs
If you suspect your dog has a cataract, an eye examination should be performed by a veterinarian. Your vet may also run tests to look for underlying health issues, particularly diabetes. Sometimes your regular veterinarian will refer your dog to a veterinary ophthalmologist, as these eye specialists have the equipment and knowledge needed to fully examine a dog's eyes.
Special lamps and lenses may be used to visualize parts of your dog's eyes and rule out other eye changes and concerns like corneal ulcers or lenticular sclerosis, which are not related to cataracts but also cause cloudiness in the eye. The stage and cause of the cataract, as well as how much of the lens is affected, will determine how much vision your dog may or may not have and whether surgery is recommended.
Surgery to remove the damaged lens is the only proven option to restore a dog's vision and prevent the cataract from progressing, but not all dogs are candidates for surgery, and it can be prohibitively expensive for many dog owners. Eye drops to prevent infection and inflammation post-operatively are normally prescribed, and most dogs will regain at least partial sight after the cataract is removed. Regular eye exams will also be needed after surgery to continually monitor the health of the dog's eye.
In some dogs with immature cataracts, eye drops to dilate the eye may be used to enhance your dog's vision. Vitamins, antioxidants, and various supplements are available to support eye health but will not make a cataract disappear. Some may also lack scientific evidence of efficacy. One product called Kinostat has shown some promising results to delay cataract progression. It is only for diabetic dogs and requires lifelong administration to help prevent the progression of cataracts but will not dissolve them, however.
Prognosis for Dogs With Cataracts
Although cataracts are progressive and can eventually lead to complete or near-blindness in your dog, they are not painful and do not necessarily diminish your dog's quality of life. Because dogs depend heavily on their sense of smell to make sense of the world, they often are able to compensate quite well for minor to moderate loss of vision.
If your dog eventually becomes completely blind from the cataracts, you can help it continue to enjoy life by keeping its bed and food bowls in the same place, avoiding rearranging your furniture, keeping the floors free of clutter, and alerting your dog to your presence by calling its name when entering a room. Your dog will quickly learn how to make its way around your home as long as it can count on everything staying in the expected spots.
How to Prevent Cataracts in Dogs
It is often not possible to prevent cataracts from developing in your dog's eyes, as they are most often genetic. But for dogs with cataracts caused by diabetes, keeping strict control over blood sugar levels can help prevent or delay this common eye problem. And with any dog, maintaining good health helps ward off potential health problems that could lead to cataract development as your dog ages.
At-Risk Breeds for Developing Cataracts
Some breeds of dogs can be more affected by hereditary or inherited cataracts than others. While some of these breeds are affected at birth or as puppies, many don't develop noticeable cataracts until they are adults. Over 150 breeds are at risk of developing inherited cataracts and include:
Cataracts in Dogs. Small Door Veterinary.
Davidson MG and Nelms SR. Diseases of the Canine Lens and Cataract Formation. In Gelatt KN (ed): Veterinary Ophthalmology 4th Pg 859-887. Blackwell Publishing, Ames IA.