Cataracts in Dogs

What are Cataracts in Dogs?

A cataract is an imperfection, an opacity, or a “clouding” of the lens of the eye. The function of the lens is to allow passage of light and images directly to the retina where vision occurs. The lens should be crystal clear, but diseases of the lens, like cataracts, can change its transparency or clarity.

Cataracts may be too small to interfere with vision, so large as to drastically impair vision or anywhere in between. To detect cataracts in dogs, simply look for whiteness on the pupils in one or both eyes.

Cataracts are classified by:

• The dog’s age at onset:

  • Congenital: present at birth

  • Juvenile: young dogs

  • Senile: older dogs

• Anatomic location

• Cause

• Shape

• Degree of opaqueness can be broken down even further to the following:

  • Incipient: Cataracts are so small they often require magnification to diagnose. These involve less than 15% of the lens and cause no vision loss. Many dogs won’t notice these, and surgery to remove the cataract is rarely recommended at this stage.

  • Immature: Cataracts involve more than 15% and up to 99% of the lens—often multiple layers or areas. The retina can still be seen during examination and visual deficits are typically mild. Significant vision loss usually occurs with cataracts that cover 75% of the lens, but the degree to which it affects the dog varies.

  • Mature: Cataracts involve the entire lens, and the retina cannot be seen during examination. Visual deficits are often significant, with blindness or near-blindness often detected. Dogs with mature cataracts can only see changes in light. They should undergo surgery to remove the cataracts if all other systemic illnesses are under control.

  • Hyper-mature Cataracts: the lens begins to shrink, and the lens capsule appears wrinkled. Lens-induced uveitis (inflammation within the eye) often occurs at this stage.

If cataracts occupy less than 30% of the lens, or if only one eye is affected, they rarely cause reduced vision. When the opacity covers about 60% of the total lens area, vision loss often becomes obvious. If the opacity progresses to 100% of the lens, the dog will be blind in the affected eye. Whether the cataract remains stable or progresses depends on the type of cataract, the breed of dog and other risk factors.

Hereditary cataracts occur commonly in young dogs between 1 and 5 years old. Breeds most susceptible to hereditary cataracts are:

• American Staffordshire Terrier

• American Cocker Spaniel

• French Bulldog

• Labrador Retriever

• Miniature Poodle

• Miniature Schnauzer

• Boston Terrier

• Siberian Husky

• Yorkshire Terrier

• Welsh Springer Spaniel

Cataract that dissolve on their own without treatment is referred to as cataract dissolution, and can cause deep inflammation within the eye. The cataract completely blocks light from entering the eye through the lens and keeps your dog from seeing. The condition is still treatable at that time with surgery, but without treatment, the condition can develop into glaucoma.

Glaucoma happens when fluid in your dog’s eye doesn’t drain properly, causing a painful increase in the pressure of the eye. Not all untreated cataracts develop into glaucoma, but dogs who have glaucoma are often not candidates for cataract removal surgery. Medical and surgical treatments exist for glaucoma, but in general, it carries a poor prognosis for preserving long-term vision.

Symptoms of Cataracts in Dogs

Puppies with complete juvenile cataracts won’t be able to see well and may start bumping into things. You may also see that the middle of the pupil has a white spot.

Bring your dog to the veterinarian if you see any signs that the eyes have changed in color or clarity. Also, if puppies are squinting or scratching at their eyes, or showing any signs of illness, bring them to the veterinarian as soon as possible.

When dogs have a cataract, it distorts their vision. Therefore, symptoms are usually related to the degree of vision loss. A cataract can start out the size of a pinpoint and grow to the size of the entire lens, and cause blindness. Dogs with less than 30% lens opacity will display few - if any - symptoms, even though there might be a visible lesion on the eye.

Cataracts cause dogs to experience disorientation or confusion if the cataracts develop quickly, such as with diabetes mellitus. Inflammation associated with cataracts can be painful and lead to glaucoma, which is even more painful. The pain is from the body reacting to what is perceived as a foreign substance on the lens. If the cataracts are caused by diabetes mellitus, you may also see increased thirst and urination, changes in appetite, and/or weight loss in your dog, along with lesions on the eyes and associated vision loss.

Causes of Cataracts in Dogs

The most common cause of cataracts in dogs is hereditary/genetic disease. Cataracts also occur commonly in dogs as a complication of diabetes mellitus. There are other causes that are much less common, such as:

• Old age

• Trauma, such as electric shock

• Inflammation of the eye’s uvea (uveitis)

• Low blood calcium levels (hypocalcemia or hypoparathyroidism)

• Nutritional deficiencies (less understood, but cataracts have been linked to lack of amino acids such as Tryptophan, during development of puppies who are fed commercial milk-replacer supplements)

• Exposure to UV light (most common cause of cataracts in humans), radiation or toxic substances

Cataracts that are secondary to diabetes mellitus are increasingly common in dogs. The increased blood glucose causes sugars within the lens of the eye to accumulate. Normally, these cataracts develop quickly and can rupture the lens capsule. If the cataract is a result of diabetes mellitus, it's possible to slow the progress by changing your dog’s diet and insulin intake. If the cataract has progressed far enough, surgery might also be an option.

How Veterinarians Diagnose Cataracts in Dogs

If you notice a cloudiness in one or both of your dog’s eyes, it’s important to have the dog examined by your veterinarian as soon as possible. The vet will ask about your dog’s medical history and previous health concerns, including when you first noticed the symptoms, and conduct a complete physical examination to focus on the eyes and structures around the eye. Initial diagnostic testing (such as a complete blood count, serum biochemistry profile and urinalysis) usually do not show any abnormalities unless there is co-existing disease, such as diabetes mellitus or hypocalcemia.

During the initial eye exam, your vet will use several tests to make a diagnosis of cataracts. These preliminary test results will also establish a baseline for comparing your dog’s progress over time. It will be necessary to dilate your dog’s eyes to get a better look at the outside edge of the cataract and the back of the eye (if possible). Cataracts should also be differentiated from other lens imperfections in young dogs and the normal increase in nuclear density (otherwise known as nuclear sclerosis) that occurs in older animals. Tests include the following:

• Slit lamp biomicroscopy: A special light is shone in the dog’s eye, which allows for direct examination of the lens.

• Schirmer tear test: A small filter paper is placed inside the dog’s lower eyelid. When the paper is removed, it is tested for moisture content to measure tear production.

• Fluorescein stain: Usually neon orange or yellow, ocular stains are used to evaluate the integrity of the surface of the eye, looking for defects to the cornea, such as scratches or the presence of any foreign materials.

• Tonometry: After numbing the surface of the eye with an eye drop, the vet uses a small “pen” to tap the surface of the eye to measure intraocular pressure.

If your veterinarian is unable to do these tests, or the test results indicate an abnormality, you will be referred to a board-certified veterinary ophthalmologist in your area.

If based on the state of the eyes and the appearance of the cataracts, it is decided that cataract surgery is needed, further testing will be done to ensure that the retina (the structure in the back of the eye that processes light information and sends it to the brain) is healthy. Some cataracts occur secondary to or are associated with loss of retinal function or retinal detachment.

Pre-operative tests to evaluate the retina include an electroretinogram (ERG) and an ocular ultrasound to measure the electrical responses of cells present in the retina. These tests usually require your dog to be sedated and can take a few hours. If retinal function is compromised, this will affect your dog’s ability to see well - even after cataract removal. In these cases, cataract surgery is not recommended.

Treatment of Cataracts in Dogs

There are no medical therapies currently available to reduce or “cure” cataracts. Currently, surgery is the only option. Research is ongoing into a few topical eye medications including topical aldose reductase inhibitors (ARI eye drops) have shown some success in cataracts caused by diabetes mellitus.

To guarantee the best chance of restored vision after cataract surgery, the health of both the eyes and the dog are evaluated. This step is critical, as any underlying diseases such as a skin or a dental disease should be under control prior to cataract surgery.

Cataracts are a progressive disease, and if surgery is recommended, it should be done in a timely manner. Pre-operative medication must begin and continue for several days to a few weeks prior to surgery to make sure any inflammation in the eyes associated with the cataracts is controlled. The long-term success rates reported in dogs following uncomplicated cataract surgery range from 85–90%.

The only definitive therapy for cataracts is removal of the diseased lens using a modern cataract surgical method called phacoemulsification. This surgical procedure involves the emulsification, or liquefying, of the eye’s lens with an ultrasonic probe. Once the lens is liquified and removed, fluids are replaced with a balanced salt solution. A corrective or artificial lens, similar to a contact lens, may be implanted on the eye during surgery. This new lens will be permanently attached to the eye.

Cost of Surgery for Cataracts in Dogs

Estimated costs are as follows:

• Initial exam with an ophthalmologist: $200–$300

• ERG, ultrasound and blood work: $1,000–$1,200

• Cataract surgery on both eyes: $2,700–$4,000, including pre-operative examination, surgery, anesthesia, operating room use, hospitalization, and post-operative medications.

• The average cost is $3,500, which may include a post-operative checkup as well.

Remember that these costs are only estimates and may increase or decrease depending on the nature of the cataracts, the presence of systemic disease (such as diabetes mellitus) and whether complications occur during or after surgery.

Recovery and Management of Cataracts in Dogs

After surgery, dogs are usually kept in the hospital overnight. They must wear an Elizabethan collar or inflatable cone to keep them from scratching at their eye. Owners will be given eye drops to administer to their dog at least two to four times a day while at home.

Surgery to correct a dog’s cataract involves a lifelong commitment from the owner. Dog owners looking to treat immature cataracts must start their dog on a regimen of multiple anti-inflammatory eye drops at the time of diagnosis. These drops will likely need to be used throughout the dog’s life.

The rate of progression of this disease depends on the underlying cause of the cataract, the location of cataract and the age of the dog. Cataract surgery for dogs with diabetes mellitus appears to yield the same success rate as for hereditary cataracts.

Prevention of Cataracts in Dogs

Since most cases of cataracts are hereditary, there isn’t much a pet parent can do to prevent the condition. However, feeding your dog a high-quality diet that is rich with omega-3 fatty acids can help promote eye heath. Discuss  supplement options with your vet to find the best product that is the most beneficial.

You should also be mindful of how much exposure your dog has to UV rays. You can help prevent cataracts in dogs by blocking harmful UV rays, by making sure your dog has plenty of shade while outdoors and having them wear protective goggles such as Rex Specs if you are in an area of high exposure area.