CATARACTS IN THE DIABETIC DOG
Most diabetic dogs will develop cataracts and go blind. This web page is arranged as an FAQ to assist the owners of diabetic dogs in knowing what to expect and in decision-making regarding cataract surgery.
WHAT IS A CATARACT?
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.
WHY DO DIABETIC DOGS GET CATARACTS?
HOW LONG DOES IT TAKE TO GO BLIND?
Generally the cataract has matured and the dog is blind in a matter of weeks.
Until recently, the development of blindness in a diabetic dog was basically a foregone conclusion but there is a new product called Kinostat® which has changed this. To review, the lens absorbs glucose from the fluids of the eye and uses this glucose as nutrition. Any extra glucose that is absorbed into the lens is converted to sorbitol by an enzyme called aldose reductase. Sorbitol pulls water into the lens to prevent the lens from becoming dehydrated. This is all well and good but in the diabetic state there is lots of excess glucose and the excess glucose gets converted to excess sorbitol which, in turn, pulls so much water into the lens that clarity and function are disrupted and a cataract is formed. Kinostat is an aldose reductase inhibitor which curtails the production of sorbitol. Early use of Kinostat may significantly delay or even completely prevent the development of cataracts.
Kinostat is a preventive only and will not reverse cataract formation that has already occurred. Kinostat is unfortunately not yet commercially available.
WHAT DOES IT MEAN TO SAY THAT A CATARACT IS “MATURE?”
All cataracts do not progress all the way to hypermature and may stay static or progress at changing rates; however, diabetic cataracts are notorious for reaching hypermaturity and creating inflammation.
WHAT IS “UVEITIS?”
Uveitis is inflammation of the “uveal tract” of the eye, which consists of the vascular tissues of the eye. In this situation, uveitis is the inflammation that results when the hypermature cataract begins to liquefy. Uveitis is painful and tends to cause the eye to become reddened and the pupil to constrict. When uveitis is present prior to surgery, success (pain-free vision) is present in only 50% of cases 6 months after surgery as opposed to 95% of cases for whom there was no uveitis preoperatively.
CAN MY DOG'S VISION BE RESTORED?
IS IT CRUEL TO KEEP A BLIND DOG?
Not at all. Dogs do not depend on vision the way humans do. A blind dog can get a long very well as long as the furniture isn’t moved and the dog is properly supervised.
For tips on helping the blind dog adapt:
There are many medical conditions that render a dog blind and as long as the condition is not painful, the dog can live a normal life as a successful and happy pet.
REGARDING CATARACT SURGERY, WHAT IS THE FIRST STEP?
The first step is a consultation with your regular veterinarian. Your dog’s diabetes must be well regulated before surgery is considered. If pre-operative lab tests show nothing to preclude anesthesia, the next step is referral to a veterinary ophthalmologist. Your regular veterinarian can do this or you may search on your own at
(Web site of the American College of Veterinary Ophthalmologists).
WHAT HAPPENS WITH THE OPHTHALMOLOGIST?
It is necessary to determine if the eye is going to be visual after cataract surgery. There is, after all, no point to performing this surgery if the eye is going to be blind anyway. The most important test is called an “ERG” (an electroretinogram). This test checks the retina for electrical activity which, if present, indicates the eye should be able to see after the cataract in front of it is removed.
In addition to performing the ERG, the ophthalmologist will be checking for uveitis. Uveitis should be treated prior to surgery to minimize the inflammation that is inevitable after surgery.
WHAT KIND OF AFTER CARE IS NEEDED?
The patient will need to wear an Elizabethan collar after surgery to protect the eye. Cortisone eye drops are needed for probably several weeks. Oral anti-inflammatories will be needed for weeks to months after. Drops to keep the pupil dilated will also be used.
WHAT KIND OF COMPLICATIONS ARE POSSIBLE?
Complications to consider are:
SHOULD BOTH EYES HAVE SURGERY?
It is important to remember the old saying that the one-eyed man is king among the blind. A dog need only have one cataract removed to have vision restored. Doing both eyes is an option to discuss with the ophthalmologist as some dogs need all the vision they can get.
Cataract surgery requires committed patient care both in the hospital and at home. Surgery also requires a financial commitment (which varies regionally and between different practices); your regular veterinarian can get a sense for average costs in your community when you are ready to consider restoration of your dog’s vision.
Page last updated: 8/20/2021