Cataracts in dogs is a condition where the inner lens of the eye
becomes cloudy. The cloudiness is caused by alternations in the fibers
that make up the eye lens due to problems with lens nutrition,
metabolism, protein synthesis, energy metabolism or fluid pressure in
the eye (osmotic balance problems, caused by diabetes).
This partially or completely blocks light from getting to the retina, the part of the eye that generates images. Cataracts can appear in small spots, a haze across the lens or as white streaks. It can cover a small area and then spread over a larger surface. The disease appears to progress faster in younger dogs. How fast it spreads is unpredictable. It can occur in any breed at any age, and in one eye or both.
If left untreated, cataracts can lead to blindness. The disease can also trigger glaucoma, a painful dog eye condition, and scarring in the eye (from allergy to the cataracts).
Causes of Canine Cataracts
Cataracts in dogs has several possible causes including:
- Inherited from parents (genetic cataracts can start as early as
age 6 months)
- Changes in lens nutrition (caused by uveitis
or eye inflammation)
- Diabetes that impacts the osmotic balance in the eye lens (see below)
- Injury from a blunt or sharp object that disrupts the anterior
lens capsule, common in puppies
- Exposure to toxic substances
- Radiation (related to treatment in the head area)
- Electric shock
- Uveitis (inflammation inside the eye)
- Nutrition (unbalanced nutrition in puppy milk replacement)
- Unknown cause
Cataracts and Diabetes
In dogs with diabetes, 75% will develop cataracts within 1 year. The diabetes causes blood sugar levels to rise, affecting the osmotic balance in the eye lens. The enzyme aldose reuctase inhibitor causes the sugar to become trapped in the lens, causing fluid buildup and protein changes in the eye. This leads to lens fiber swelling that results in cataracts in dogs. Some diabetic dogs that are being actively treated will still develop cataracts.
In diabetic dogs, early signs of cataracts include excessive urination (polyuria) or abnormal thirst (polydipsia).
Incidence of Cataracts in Different Dog Breeds
There is a higher incidence of dog cataracts in 60 dog breeds with a 15% higher incidence in mixed breeds over age 7. Some breeds have an incidence of genetic cataracts as high as 10%.
- Siberian Huskies
- Miniature Schnauzers
- Golden Retrievers
- Labrador Retrievers
- Boston Terriers
- Cocker Spaniels
- Silky Terriers
Source: Anka Friedrich/Wikipedia
Dog Cataracts Symptoms and Signs
Vision problems do not occur until the disease is in an advanced stage, which is why annual visits to the Veterinarian are critical to catch the disease early.
Dog owners should watch for signs that indicate a problem with sight such as:
- Bumping into furniture that has recently been moved
- Reluctance to go down stairs
- Seeming to forget the location of water or food bowls
Owners should also look for the characteristic cloudy lens appearance.
Canine cataract diagnosis starts with a complete eye examination to determine if treatment will help the eye. The eye will be examined with a device called an ophthalmoscope, which is a light attached to a magnifying glass. This will be followed by the use of eye drops to test for eye pressure and ulcerations of the eye.
An ultrasound can evaluate the condition of the lens capsule and check to see if the retina is detached. Prior to surgery a test called an electroretinogram is used to evaluate degeneration of the retina.
First, the veterinarian will determine if the patient is a candidate for surgery, since this is the preferred method of treatment. Dogs will be assessed based on their overall health, presence of other inflammatory eye conditions or if the dog has diabetes. The veterinary opthalmologist will also check to make sure that the retina is functioning and healthy.
Dog Cataract Surgery
The surgical procedure itself is called phacoemulsification. The procedure involves the use of general anesthesia and takes 45 to 60 minutes. The veterinarian will remove the eye lens, replacing it with an artificial lens.
The success rate for dog cataract surgery is 80% to 95% with good vision. Once surgery is completed vision will gradually improve over several days. Full recovery is reached in 6 weeks. After surgery dogs are fitted with a preventive cone shaped clear collar to prevent scratching and so that the dog can see.
After surgery, you will have to administer eye drops into your dogs eyes for several weeks. During the first 6 weeks drops need to be given multiple times per day.
Once blindness sets in to one eye and if it starts in the other eye, then surgery in both eyes is called for. It has been performed successfully on dogs between the ages of 6 months to 18 years (assuming your dog is in good health).
Dog Cataracts: Medicine
No medications are available to treat or prevent dog cataracts.
If a dog is not a good candidate for surgery, the opthalmologist will assess the dog's condition 1x to 2x per year to monitor the progress of the disease. The veterinarian will monitor for conditions such as inflammation (uveitis), or glaucoma (high blood pressure). Glaucoma in particular can be painful for the dog.
In the case of diabetes, drops called aldose reductase inhibitors have shown some success in slowing the progression of the disease if caught early enough.
There is some controversy around eye drops called Oculvet which claim to treat canine cataracts. This treatment is expensive ($91 per bottle) and the scientific evidence that it works is still under debate or refuted by many veterinarians. (1)
For Additional Reading:
(1) Cornell University College of Veterinary Medicine, Dogwatch
(3) Washington State University School of Veterinary Medicine