Dogs don’t see the world the same way as humans. For example, dogs can’t see the full rainbow of colors most people can. At a basic level, a dog’s eye structure is the same as ours, which means sharing the same concerns regarding eye health. One concern for your dog’s eyes is cataracts. This clouding of the eye’s lens can impact your dog’s ability to see and sometimes lead to serious complications. Here’s what you need to know about cataracts in dogs, signs, diagnosis, and treatment.
What Are Cataracts?
Both your eye and your dog’s eye have a layer of tissue at the back called the retina. The retina senses light, acting like a camera’s photo sensor, and sends messages to the brain (via the optic nerve) about what the eyes can see. But light needs to be magnified and focused into the retina for a dog to see clearly. That’s the responsibility of the lens, a clear ball-shaped structure that sits inside the eyeball just behind the pupil.
According to Dr. Chantale Pinard, associate professor and veterinary ophthalmologist at the Ontario Veterinary College, a cataract is a clouding of the lens. Dogs have lenses just like humans, and they can get cataracts too. Opacity can be focal (small or pinpoint) or diffuse (encompassing the entire lens). Dr. Pinard says it is due to improper lens fiber orientation (misalignment) that reflects back light. “This improper orientation of lens fibers can start during the fetal stage or late in the pet’s life.”
What Causes Cataracts in Dogs?
Cataracts in dogs can be caused by things like nutritional impairment from the lack of arginine in a milk replacement, congenital issues where the fetus develops incorrectly, trauma or injury to the eye, or uveitis, an inflammation of the eye that results in the warping of the lens fibers. However, Dr. Pinard states that the two most common causes of canine cataracts are genetics and diabetes mellitus.
Both purebred and mixed-breed dogs may develop cataracts in their lives. Still, some dogs may be predisposed to develop cataracts earlier in their life, sometimes as young as one year old. Some dog breeds that may be predisposed to developing early cataracts are the Bichon Frise, Boston Terrier, Cocker Spaniel, Toy Poodle, Miniature Poodle, Standard Poodle, Labrador Retriever, and Siberian Husky.
Diabetes causes cataracts in dogs when there is a rush of water into the lens. This happens if the lens has a high sugar load, which can move lens fibers into the wrong positions. Dr. Pinard says, “In some cases, the development of a cataract due to diabetes can be quick and result in blindness within one week due to the presence of a complete or diffuse cataract.”
Signs of Cataracts in Dogs
You might think vision loss would be the first sign of a cataract. But that’s not the case. Incipient cataracts, which means the cataract covers less than 15% of the lens, don’t usually affect the vision in that eye. And dogs with immature cataracts, the next stage of advancement, can still have vision, although the vision won’t be normal. The final two stages of cataracts, mature and hyper-mature cataracts, will cause vision loss in the affected eye.
Dr. Pinard mentions that the first sign of a cataract might be redness in or around the eyeball. “This is due to the leakage of protein from the misaligned lens fibers. These proteins react within the eye and cause inflammation. The pet owner can see this inflammation as redness of the eye, a small-constricted pupil, and photophobia, [which is] increased sensitivity to light leading to signs of discomfort.”
When the cataract is large or spreads out, you will see a white pupil and start to see signs of vision loss. For example, the dog might bump into furniture or miss a thrown ball on the affected side. Dr. Pinard warns that losing their vision in one eye can be harder for dog owners to detect since your dog can still use their other eye to see.
Is It a Cataract or Nuclear Sclerosis?
A hazy pupil doesn’t always point to dog cataracts. As dogs age, they can develop a bluish-tinged pupil as the lens fibers compress. Known as nuclear sclerosis or lenticular sclerosis, this is a natural, age-related condition that usually appears once the dog is over seven years of age. “Nuclear sclerosis can diminish vision in low-light environments but should not impede vision in normal, bright-light environments,” Dr. Pinard says.
How Does a Veterinarian Diagnose Dog Cataracts?
Your veterinarian will do an eye exam to diagnose cataracts. Small cataracts can be hard to detect, so your veterinarian might dilate the pupils to help see as much of the lens as possible.
“By shining a light and using head loupes or a direct ophthalmoscope, a veterinarian will examine the lens and detect opacities, whether they be small or large,” says Dr. Pinard. “The veterinarian may also elect to measure the pressure within the eye to see if inflammation from the cataract is lowering the eye pressure.”
Treatment for Cataracts in Dogs
If a dog’s vision isn’t affected by the cataract, your veterinarian will likely advise monitoring the situation. If inflammation is present, anti-inflammatory eye drops will be prescribed to keep the eye as healthy and pain-free as possible. You’d need to continue administering these drops as long as the cataract is present.
“There are claims of having eye drops stop or reverse the progression of cataracts,” Dr. Pinard cautions. “Unfortunately, if this was truly the case, then cataract surgery would stop, and [many] dogs would be on these drops.”
Cataract Surgery for Dogs
If your dog’s sight is affected, cataract surgery is the only treatment for restoring their vision. The surgery will be performed by a veterinary specialist from the American College of Veterinary Ophthalmologists. Dr. Pinard explains that cataract surgery is expensive and can come with complications, so if your dog can function visually, your veterinarian might not immediately refer them as a candidate for surgery.
“The surgery requires general anesthesia, specialized equipment, and frequent re-checks. These complications can be severe and may result, in a small percentage of patients, in the removal of the eye for patient welfare. Fortunately, these severe complications are uncommon, and the surgical success is estimated at approximately 80 to 90 percent with a 10 to 20 percent complication rate.”
Surgical removal of the cataract and replacing the lens with a new artificial one can almost completely restore your dog’s vision. After surgery, your dog will need several weeks to months to recover. But then they will be able to stare into your eyes and catch their ball just like they used to.