When you look into your dog’s eyes, what should you see? If your pet is healthy, bright, shiny and clear eyes should be looking back at you. (Well, OK… those three qualities plus a pleading expression, begging for that last bite of whatever it is you are eating.) However, if your dog’s eyes begin to look a little cloudy or bluish-gray, it could indicate that cataracts are forming, which is a sign for you to take him or her to your veterinarian for further evaluation.
So, just what is a cataract?
Cataracts are characterized by the development of opacity in the lens of the eye. The lens is the normally clear structure that sits directly behind the iris (the colored part of the eye), and its job is to focus light as it moves toward the back part of the eye (the retina). Despite its clarity, the lens is in fact made of tissue fibers. As an animal ages, these fibers become more dense and compact, preventing the passage of light to the retina, leading to blindness.
What causes them to develop?
The most common cause of cataract formation is due to hereditary disease. Other causes include congenital (born with it), senile cataracts (age-related), diabetes, trauma, dietary deficiency (milk replacement formulas that are low in arginine or phenylalanine have been implicated as well as puppies fed strictly evaporated milk formulas or goats milk), electric shock or toxins.
Why is it bad to have a cataract?
A cataract by itself does not necessarily require treatment. If the only problem is blindness, and there is no associated inflammation or glaucoma, it is perfectly reasonable to have a blind pet, as dogs do not depend on vision the way humans do. Blind animals can have an excellent life quality and can adjust well to vision loss (though it is important not to move furniture around or leave any hazardous clutter in the home). Some dogs, however, do become anxious—or even aggressive—when they lose their vision.
Of bigger concern is the fact that a cataract can luxate, meaning it can slip from the tissue strands that hold it in place and end up floating around in the eye, causing damage. Furthermore, if a cataract settles in a place blocking the natural fluid drainage of the eye, a buildup in eye pressure (glaucoma) can result, leading to pain and permanent blindness.
Another problem is the fact that cataracts can begin to liquefy and dissolve after a long time. While this sounds like it should be a good thing, it is a highly inflammatory process, and creates a condition called uveitis. This is a very painful eye disease that can also lead to glaucoma.
How are cataracts treated?
Cataract treatment generally involves surgical removal or physical dissolution (“breaking up”) of the cataract under anesthesia. The ideal time for cataract surgery is the immature or early mature cataract stage.
Obviously, the pet must also be in good general health to undergo treatment. For example, a diabetic dog must be well regulated before cataract surgery. Also, in order for a pet to be a good surgical candidate, he or she must also have a temperament conducive to having eye drops administered at home. Lab work is performed prior to anesthesia and some ophthalmologists also request that pets have their teeth cleaned prior to surgery to minimize sources of infection for the eye.
Historically, removing the cataract meant surgically cutting into the eye and physically removing the lens. (This short video shows a cataract removal—not as daunting as one would think!) This is still done for older patients whose lenses are compact, but for younger patients where the lens is still soft, a technique called phacoemulsification is preferred.
This technique has become the most common method of removing cataracts in dogs. Here, the lens is broken apart by sound waves and sucked out with a gadget similar to a tiny—a few millimeters wide—vacuum cleaner. Artificial lenses are implanted at the time of surgery, restoring essentially normal vision. (Without the artificial lens, the dog’s vision will be approximately 20/800, and objects will appear to be reversed, as in a mirror.)
Cataract surgery is performed routinely with an overall 80 to 90 percent success rate. Long term prognosis following cataract surgery is very good to excellent. Overall, a 95 percent vision rate is reported immediately after cataract surgery, and once cataracts are removed, they cannot return!
What else could it be?
During exams, people often raise the concern that a cataract is developing in their pet’s eye. Generally, the vast majority of the time the pet does not have cataracts, but instead has the much more common condition known as nuclear sclerosis.
Nuclear sclerosis is a normal change that occurs in the lenses of older dogs and it appears as a slight graying of the lens. The older, denser lens begins to appear cloudy. It usually occurs in both eyes at the same time and occurs in most dogs over six years of age. The condition does not significantly affect vision and treatment is not needed.
How your veterinarian can tell the difference between a cataract and nuclear sclerosis is by shining a bright light into the eye. With a cataract, you are unable to see to the back of the eye (the retina); with nuclear sclerosis, you can still see the retina. In the pictures below, you can see how easily nuclear sclerosis (left) might be mistaken for a cataract (right).
If you observe cloudiness in one or both of your dog's eyes, you should bring him or her to see your veterinarian for further evaluation. Your veterinarian can perform a complete physical examination, focusing on the eyes, helping to determine the severity of the problem. Restoring vision for your pet can then be weighed against risk and expense, and it is a personal decision for each family to make.