One of the most devastating side effects of diabetes mellitus in dogs is blindness from cataracts. In dogs with normal sugar metabolism, glucose in the lens is metabolized by an enzyme called hexokinase into small molecules that diffuse out of the lens. When the glucose levels are high, hexokinase cannot keep up and the excess glucose is metabolized by aldose reductase into sorbitol. Sorbitol is a large molecule that cannot diffuse out of the lens. It causes water to migrate into the lens leading to swelling and cloudiness. Within a short time, there is so much sorbitol in the lens that light cannot penetrate through the lens to the retina in the back of the eye and the dog becomes blind. The only treatment available at this point is surgical removal of the lens.
Until recently, good glycemic control was the only method of preventing sugar cataract formation. Now there is a new drug called Kinostat ™ to help out these dogs. Kinostat™ blocks aldose reductase which prevents the formation of sorbitol. The drug is currently in phase 3 clinical trials at several veterinary ophthalmology clinics across the United States. Hopefully, it will be available soon.
Kadon P.F., et al., “Topical KINOSTAT™ ameliorates the clinical progression of cataracts in dogs with diabetes mellitus” Vet Ophthalmol Nov. 2010;13(6):363-8.
Several months ago, I performed an annual exam on a lovely Chihuahua mix. This handsome boy let me look in his mouth, listen to his heart and feel his abdomen. Look at the picture below and then answer the following questions: What is wrong with this dog’s eyes? Does it affect his vision? List some of the common causes?
Cataracts is the term used to describe cloudiness of the lens of the eye. When the condition is mild, the dog can still see through the lens although their vision is blurry. As the cataracts progress, less and less light is transmitted through the opaque lens resulting in blindness. Unfortunately, this dog is functionally blind from the cataracts but his owner reports he gets around well at home. Since he developed cataracts, they have been careful to keep everything the same in their house. The two most common causes of cataracts I see in practice are inherited, even in mixed breeds like this one and diabetes mellitus.
Pets love their people unconditionally. As a veterinarian, I see their unconditional love displayed in a variety of ways. Most of my patients still like me even after an uncomfortable treatment. I am amazed by how many dogs wag their tail for me after I vaccinate them. Cats often rub their faces on me and purr after I take their temperatures. And then there is the bond between pets and their people…
Last week, a wonderful cat named Mat lost his fight with cancer. Mat didn’t really like coming to see me. He would complain loudly when I examined him. When I listened to his heartbeat through my stethoscope, his heart raced. It raced until he saw Brian. When Mat heard Brian’s voice or saw his face, his heart rate slowed and he started to purr. Brian loved Mat and Mat dearly loved Brian. It was clearly a match made in heaven.
So today I would like to celebrate the human-animal bond. Seldom has it been expressed so beautifully as between Mat the cat and his best friend Brian.