News you can use: Cataracts in Dogs-How does your dog really see you?

Have you ever looked into those two beautiful, shiny eyes of your pet and noticed something different inside their eyes? There are a number of conditions that can occur inside your pet’s eyes, and today we will explore one of the most common ones, cataracts.

What is a Cataract?

Like a camera, eyes have a clear lens inside them that is used for focusing. A cataract is any opacity within/on a lens. The opacity can be very small (incipient cataract) and not interfere with vision. It can involve more of the lens (immature cataract) and cause blurred vision. Eventually, the entire lens can become cloudy, and all functional vision lost (mature cataract). Some mature cataracts will transform over time into hypermature cataracts. Hypermature cataracts usually are reduced in size due to loss of water and proteins from the lens. This causes the lens to shrivel and the lens capsule to wrinkle—similar to a grape turning into a raisin. Hypermature cataracts vary in how cloudy they are. Some are completely cloudy, and others have clear areas that can allow for some vision if the rest of the eye is functional. Depending on the dog’s age and breed, it can take several months to years for a mature cataract to turn into a hypermature cataract.

What is not a cataract?

All geriatric dogs (usually beginning at 6 years of age) develop a hardening of the lens (called Nuclear Sclerosis) that causes the lens to have a grayish appearance. The grayish-blue haze increases as the dog ages. Nuclear sclerosis is NOT a cataract, and does not usually interfere with vision. Nuclear sclerosis also occurs in humans, and the hardening of the lens with age results in reduced near-vision in people; this is why people in their 40’s and older need reading glasses—because their lenses no longer are soft enough to easily change shape to allow for near vision. Dogs do not have good near-vision to begin with (compared to people), so nuclear sclerosis does not significantly interfere with their near-vision.

How do you tell the difference between nuclear sclerosis and cataract in your dog? The answer is that you can’t. You can start with having your family veterinarian evaluate your dog’s eyes. However, veterinary ophthalmologists are the best suited to tell the difference between nuclear sclerosis and cataracts, using specialized equipment and their expertise. Also keep in mind that dogs can develop BOTH nuclear sclerosis AND cataract.

What causes cataracts?

The most common cause of cataracts in the dog is inherited disease and can happen at any age. The second-most common cause of cataracts in dogs is diabetes mellitus ("sugar diabetes"). 75% of diabetic dogs will develop blinding cataracts within the first nine months of being diabetic. Often, the cataracts form very shortly after the dog becomes diabetic. Other causes for cataracts are a toxic reaction in the lens (toxic cataracts), due to some other ocular disease or due to a drug reaction. Trauma (such as a cat claw injury or pellet gun injury) can also cause the lens capsule to rupture and a cataract to form on the lens. Cataracts can also develop due to nutritional deficiencies in dogs, such as puppies on an artificial milk-replacer diet. These are called nutritional cataracts, and they often will improve as the puppy matures.

Are some breeds more prone than others?

Hereditary cataracts can affect many breeds of dogs. Some of the recognized breeds include the American Cocker Spaniel, Labrador Retriever, French Poodle, Boston Terrier and the Welsh Springer Spaniel to name a few.

How are cataracts treated?

Once a lens has developed a cataract, there is no known method to make the lens clear again. Immature, mature, and hypermature cataracts can be treated by surgically removing them.

However, nutritional support of the lens can help to prevent, slow down or lessen the severity of developing cataracts. Nutritional supplementation can help to enhance lens health by providing oral antioxidants designed specifically for support of the canine eye.

Cataract surgery is one of the most common surgeries performed on humans. However, not all dogs with cataracts need or should have cataract surgery. In fact, most dogs with cataracts do not need surgery, because most lens opacities in dogs are small and don’t significantly interfere with vision. Just because a dog’s eye has a cataract does not mean that the dog must undergo cataract surgery. Only a veterinary ophthalmologist can determine if cataract surgery is indicated in an affected patient.

Learn more about

Amanda Barbosa, DVM

References:

Gelatt, Kirk N., VMD, Essentials of Veterinary Ophthalmology, 3rd edition, © 2014.

McCalla, Terri L., DVM, MS, DACVO, Cataracts and Cataract Surgery in Dogs, © 2015.