Cataracts in Dogs

The lens of an eye is composed of water and proteins, and is normally clear. If something interferes with these proteins it can result in changes which lead to an opacification of the lens- a cataract. Cataracts are a common eye disorder in dogs, especially for some breeds and dogs living with diabetes mellitus.

Smaller cataracts may not have an impact on eyesight, however larger ones block vision through the affected area of the lens. Dogs do not rely on their sight as much as people do, and when a cataract forms gradually it may not have an appreciable impact on the dog’s quality of life, even if it results in complete vision loss.

In cases where a dog has pre-existing diabetes mellitus, cataracts are likely to form more quickly, grow significantly large, and affect both eyes. In these cases, dogs are often unable to properly adapt and will have a harder time coping with complete vision loss. This may escalate the importance of surgical treatment for the cataracts, which must be pursued early in their development. There is a window of time when it’s best to do cataract surgery, and pet parents interested in this option should not delay seeking an evaluation by a veterinary ophthalmologist.

Cataracts can also form in cases of ocular inflammation, such as glaucoma or uveitis.

Cataracts are not to be confused with lenticular sclerosis. The lens of a dog’s eye naturally thickens with age. Some haziness to the pupil as it grows older is expected, and not representative of cataracts. Lenticular sclerosis occurs with almost all dogs as they age, whereas cataracts are less common.

Dogs are good at adapting to gradual vision loss- even to the point of complete blindness. Dogs don’t usually show any symptoms of vision loss unless both eyes are affected. Symptoms of vision loss are more likely to be apparent in unfamiliar areas, or if the cataracts form more quickly.

Symptoms of vision loss in dogs include

• Hesitancy in unfamiliar areas
• Reluctance to move
• Bumping into things
• Distress
• Difficulty navigating different levels, such as stairs, or entering/exiting a vehicle

In some cases a cataract results in complications such as a prolapsed lens, or another ocular condition such as glaucoma. These require surgical intervention.

Rarely, untreated cataracts may dissolve on their own, and this process leads to inflammation inside the eye (uveitis). It is important to not ignore cataracts that seem to have disappeared.

Cataracts form in response to a wide variety of conditions. Genetic predisposition is the most common factor in canine development of cataracts, and diabetes mellitus the second most common. A dog can be born with cataracts (congenital), or have them develop as they age. Cataracts can also be caused by injury, dietary deficiencies, or exposure to toxins.

Cataracts are often asymptomatic, and vary in appearance.

A cataract is commonly milky-white or crystalline in color, although others are possible. Large cataracts in the lens appear as an opacity in what would normally be the black circle of the pupil.

Cataracts are typically easily recognized. Diagnostics include:

• Complete ophthalmologic exam
• Evaluating corneal integrity (fluorescein stain)
• Bloodwork
• Urinalysis

Referral to an ophthalmologist allows for more specific diagnostics, such as an orbital ultrasound or electroretinography.

Not all cataracts require treatment. Smaller cataracts or cataracts that come on gradually are less likely to have a significant impact on quality of life.

Surgical cataract removal and implantation of an artificial lens is the preferred treatment method for cataracts causing vision loss.

Some eye drops on the market claim to dissolve or remove cataracts, but there is no evidence to support this.

Left untreated, cataracts are permanent. They only become problematic if they;

• Lead to painful complications like lens luxation and subsequent glaucoma
• The affected dog is unable to adapt to vision loss

The prognosis is generally favorable with treatment, although surgery is not always possible and can sometimes result in additional complications.

Cataracts cannot always be prevented. The best strategies to try and prevent cataracts include:

• Selective breeding
• Regular wellness exams for early identification and treatment of conditions that lead to cataracts

Diabetic cataracts are less likely to develop when the dog’s diabetes is properly managed. Cataracts are not contagious.

Cataracts are common, especially in older dogs.

• Benign neglect
• Surgery
• Environmental adaptations for vision loss
• Management of associated conditions