Eye problems in diabetic dogs are unfortunately not uncommon. Uncontrolled high blood sugar can wreak havoc on several organs of the dog's body. The eyes may suffer from many damaging effects that may cause problems such as blurry vision, cloudy eyes and even blindness. Owners of diabetic dogs should therefore take steps to prevent these problems and monitor for their signs. The formation of cataracts are one of the most common complications of diabetes. Veterinarian Dr. Ivana Vukasinovic discusses cataracts along with symptoms and treatment options.
Formation of Cataracts in Diabetic Dogs
Cataract is a very common complication of diabetes in dogs. Indeed, almost 75 percent of diabetic dogs develop cataracts. This condition is not life-threatening per se, but is certainly life-changing.
The lens of the eye in a healthy dog is transparent, while the opaque or cloudy eye is called a cataract, and this condition leads to blindness.
Cataract is usually the result of an imbalance between water and protein quantities in the eyeball. The lens contains around 68 percent of water, and if this balance is upset, more water will be absorbed causing the characteristic opacity and cloudiness. The imbalance is caused primarily by high blood sugar levels that affect every organ in the body.
It has been shown that the intracellular accumulation of sorbitol leads to osmotic changes resulting in hydropic lens fibers that degenerate and form sugar cataracts.
Cataract is the change inside the lens itself. If this change of clouding is minor and does not interfere with vision, the cataract is called incipient or immature cataract. Over time, the entire lens can become fogged and all vision is lost. This is called a mature cataract. As the cataract matures, the pupil can change its color.
Another stage is called hypermature cataracts. These are cataracts that develop over a long period during which lens shrivel inside its own capsule. Even in these cases, cataracts don’t necessarily mean blindness.
Other possible causes of cataracts in dogs include drug toxicity, progressive underlying eye diseases, trauma, nutritional imbalances in puppies, or it may develop as a symptom of the aging process in older dogs.
Diabetic cataracts are emergency conditions due to the fact that they develop quickly, in the course of a few weeks, if not just days. Surgery may be needed. Even if the surgery is not an option, an ophthalmic exam is important to help decide the course of action and treatment. Also, the owner is usually not aware of uncomfortable symptoms of cataract such as a headache and eye inflammation.
"Hyperglycemia causes increased levels of glucose in the aqueous humor. This glucose enters the lens by facilitated diffusion and as the glucose concentration in the lens increases, the anaerobic glycolysis pathway that is catalyzed by hexokinase, becomes saturated, shifting glycolysis to the sorbitol pathway."~ Dr. Gavin Kennard, board-certified veterinary opthamologist
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Left untreated, cataracts can cause uveitis, intraocular inflammation that leads to glaucoma. Glaucoma is increased intraocular pressure and can lead to inoperable states; glaucoma is a painful condition with headaches, eye pain, and watery eyes.
Almost 20 percent of patients with cataracts will develop glaucoma. Sometimes due to swollen lens, cataracts can rupture leading to emergency surgery, if possible, or even eye removing surgery if necessary.
High sugar levels affect the retina as well. This effect of diabetes on retina causes a condition called "diabetic retinopathy." In the beginning, the blood vessels in the eye start to leak causing swelling and loss of vision, and later, this leads to the retina becoming oxygen deprived.
In order to compensate for the lack of oxygen new blood vessels grow, but thin and fragile leading to new hemorrhages and leaks. This stage of diabetic effects on the eye is called proliferative diabetic retinopathy. In the last stages, blood vessels grow continuously and abnormally causing scar tissue and, at the end, a serious problem such as retinal detachment.
In general, there is little that can be done to prevent eye problems in diabetic dogs from occurring. Good management may delay the onset of the conditions, but this is difficult to achieve in dogs. Different food supplements, vitamins, and antioxidants may also help to delay the onset of diabetic cataracts, but once formed, cataracts have to be surgically resolved.
At the Vet's Office
Cataracts are diagnosed by an eye exam which include measuring the eye (intraocular) pressure, tear production measurement, staining and similar tests to establish if the animal’s vision can be improved through surgery and to establish possible secondary underlying problems or diseases.
In some cases, surgery is not an option, or, the eye will not be visual despite the surgery, which is, in that case, pointless. In cases of choosing not to have surgery, your dog will be put on anti-inflammatory drops
and possible pain medication. The final consequence of cataract is the loss of vision, but, dogs adapt pretty quickly, and with slight modifications live happily and fulfilled lives.
Diabetic cataract surgery can have more side effects in diabetic dogs than in patients not suffering from diabetes. The risks associated with this procedure include inflammation (uveitis), glaucoma, retinal detachment, infection, and trauma.
As almost half of pets are overweight or obese, and obesity is one of the primary factors leading to diabetes, proper diet is one of the best ways to prevent any of above mentioned conditions. If the condition already presented itself, proper diet, insulin and special supplements combined with exercise help regulate and maintain the condition in the acceptable levels.
" Currently, there is no efficacious medical treatment for slowing, halting or reversing the progression of cataracts. Treatment with mydriatics may temporarily restore vision in cases of nuclear cataracts, and aldose reductase inhibitors are being used experimentally to slow the progression of diabetic cataracts. However, cataracts remain a surgical problem." ~ Dr. Ron Ofri, veterinary opthamologist
About the Author
Dr. Ivana Vukasinovic is a veterinarian in Belgrade, capital city of Serbia. She received her B.S from University of Belgrade in 2012, and her master’s degree from Veterinary University, Belgrade.