Blindness is a frequent occurrence in diabetic dogs, less frequent in diabetic cats. Hyperglycemia in dogs causes both cataracts and retinopathy, either of which alone can cause blindness in a few days or weeks. Blood glucose levels as low as 250mg/dL (14.0 mmol/L) can cause blindness in dogs.
Cats are much more fortunate in this regard -- their visual systems seem to be resilient to high blood sugar, and it's unusual (but not unknown) for them to go blind from it, though retinopathy is a possibility. This source says that cats do not get cataracts as a result of diabetes.
Diabetic retinopathy is a special case of neuropathy in the optic nerve and retina, and is caused by high blood sugar. Glucose toxicity damages blood vessels that nourish the retina at the back of the eye. This progressively results in blurred vision. Severe vision loss may be preventable if the diabetic retinopathy is detected and treated early and appropriately. Treatment may maintain vision, though it rarely restores it.
Mechanisms of hyperglycemic blindness in dogsEdit
Cataracts in diabetics are caused by high blood sugar. A cataract is an opacity in the lens of the eye. The entire lens may be involved or just a part of it. The patient will not be able to see through the opacity.
The eye fluids normally contain some amount of glucose, which the lens uses to nourish its cells. When the eye fluids contain too much glucose, some is converted to sorbitol, which is absorbed by the lens but cannot be consumed. The lens becomes hypertonic and pulls extra water into the lens, which damages it and makes it lose transparency. This damage to the lens is permanent, though lens transplants are possible.
Retinopathy (see first section) is more common in dogs than cats.
It is fortunate that dogs rely so much on their senses of smell and hearing, and can therefore lead relatively good quality lives while blind.
Dogs with diabetes have more "at risk" eye problems, other than cataracts and blindness. They can be prone to recurring or nonhealing ulcers of the eyes. This 2003 study found that dogs with diabetes have significantly reduced sensitivity of their corneas. This means that the nerves of the corneas do not function normally. The study indicates this to be true no matter what the glycemic control is and length of time with diabetes.
Blindness in diabetic catsEdit
People (and possibly cats) with diabetes (and especially those with Chronic renal failure) are more prone to suffering from hypertension (high blood pressure) than their non-diabetic counterparts.
Abnormally dilated pupils over a few days may mean it's time for a blood pressure check at the vet's. High blood pressure (hypertension) in cats can cause blindness, severe renal (kidney) damage, and other bodily damage.
The problem with hypertension in animals, as in people, is that there are no overt symptoms--no signs of not feeling well--until the disease is far-advanced. According to Dr. Lisa Pierson, all cats with CRF should have their blood pressure monitored. Many vets do not have blood-pressure monitors, so check around.
See the Long Beach Animal Hospital link for the use of Doppler equipment for measuring feline blood pressure, and download a QuickTime movie of the Doppler unit in action.
- Hypertension in cats
- Long Beach Animal Hospital on Hypertension in cats
- Veterinary Review August 2004 Pages 28 & 29 Feline Hypertension The publication serves all UK vets.
- Management of Systemic Hypertension in Cats-WSAVA-2001
- Ocular Manifestations of Feline Systemic Diseases-WSAVA 2005
- Ocular Manifestations of Feline Systemic Diseases-WSAVA 2003
- Diabetes Mellitus & Bilateral Cataracts in a Kitten-Journal of Feline Medicine & Surgery-2002
- Indirect Blood Pressure Measurement in Cats with Diabetes Mellitus, Chronic Nephropathy and Hypertrophic Cardiomyopathy-Tierarztlische Praxis Ausgabe K Kleintiere/Haustiere-1998-Abstract in English
- Prevalence of Feline Cataract:Results of a Cross-sectional Study of 2000 Normal Animals, 50 Cats with Diabetes and One Hundred cats Following Dehydrational crises Veterinary Opthalmology 2006
- Feline Hypertension: Risks & Management-WSAVA 2005
- Long Island Veterinary Medical Association April 2005 Non-Surgical "Cataract Cure"-Page 34
Note: pdf is huge--almost 10MB. Includes photo of cat with cataracts before & after surgery. Author is also ACVO Board-Certified.
- Feline Hypertension: Clinical Features and Therapeutic Strategies-WSAVA 2004
- Cataracts in Cats-Petplace.com
- Ubiquitous but Clinically Mild Feline Cataracts-North American Veterinary Conference 2007
- Wiki cases--Canine Blindness
- Cataracts in the diabetic dog
- Non-steroidal anti-inflammatories prevent retinopathy in diabetic dogs
- Keratoconjunctival Effects of Diabetes in Dogs-Veterinary Opthalmology-2005
- A Look at Some of the "Miracle Cures" for Canine Cataracts--All Animal Eye Clinic-Dr. Kerry Ketring-Board-Certified-American College of Veterinary Opthalmologists
This 35 page pdf is absolutely current in its presentation of cataract "miracle cures" being marketed.
- Effect of Chronic Hypertension on Renal Function in Dogs-WSAVA 2003
- Diabetes & Ocular Lesions in Dogs-North American Veterinary Conference-2006
- Cataracts in Dogs-Petplace.com
- Dorlands Medical Dictionary--Keratitis-of the Cornea
- Dorlands Medical Dictionary-Conjunctiva Definition
- American College of Veterinary Opthalmologists-Cataracts
- Insuman Basal package insert found here as a PIL--Patient Information Leaflet-- refers to human vision loss through severe hypos.
- Ocular Pharmacology-WSAVA 2005
- Ocular Manifestations of Systemic Hypertension in Dogs and Cats-WSAVA 2002
- Hypertension in Renal Diseases and Failure. The Practical Aspect-WSAVA 2002
- Diseases of the Lens in Dogs and Cats-WSAVA 2004
- Conditions of the Lens-WSAVA 2003
- Cataracts-WSAVA 2002
- Diabetic Cataracts: Different Incidence Between Cats & Dogs-Schweizer Archiv fuer Tierheilkunde-Abstract in English-2000
- Dog ear infection
- Pancreatitis in dogs
- Ivermectin for dogs
- How long are dogs pregnant
- Why do dogs eat grass
- Purina dog chow coupons
- ↑ Cats, Diabetes & Cataracts
- ↑ Cataracts in Dogs-Drs. Foster & Smith Pet Education Library
- ↑ Canine Diabetes & Eye Problems
- ↑ Complications Discussion
- ↑ FDMB-Abnormally dilated pupils
- ↑ Feline Systemic Hypertension--WSAVA 2003
- ↑ Photo of Blindness Caused by Hypertension
- ↑ Blood Pressure Assessment in Healthy Cats and Cats with Hypertensive Retinopathy-American Journal of Veterinary Research-2004
- ↑ Feline Hypertension: Risks & Management--WSAVA 2005
- ↑ Long Beach Animal Hospital Feline Hypertension/Doppler Equipment