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Blindness in Dogs With High Blood Pressure

 

High blood pressure in dogs is not as commonly seen as in humans, but when it occurs, it’s often indicative of underlying disorders and complications such as blindness in dogs with high blood pressure. If your dog has suddenly gone blind, your veterinarian may have tested your dog for high blood pressure. It’s important to recognize that in dogs high blood pressure tends to mostly occur secondarily to other disorders, and therefore, it’s important finding the underlying cause. Lowering your dog’s high blood pressure and tackling the underlying problem is key to preventing further complications.

Blood Pressure in Dogs

Just as in humans, dogs can suffer from blood pressure problems, and just as in humans, blood pressure can be read using a cuff that restricts a peripheral artery.

In dogs, blood pressure is taken from either a leg or the tail and the blood pressure should not exceed a systolic pressure of 180 mm Hg and a diastolic pressure of 95 mm Hg.

Most eye problems in dogs associated with high blood pressure tend to be associated with systolic readings over 200mm Hg, observes veterinarian Rhea V. Morgan in the book “Small Animal Practice Client Handouts.

Interestingly, in dogs diastolic numbers may not be worrisome as seen in humans. In humans, elevated diastolic numbers are associated with arteriosclerosis, which is a condition that does not happen in dogs, explains veterinarian Dr. Rebecca.




It’s important to note that the stress of being in a vet’s office (white coat phenomenon) may induce false high blood pressure readings in dogs. The stress can be lowered by measuring the dog’s blood pressure in a quiet area, with minimal restraint and in the presence of the owner. Dogs should also be given time to get acclimated to their surroundings. Repeated readings are often necessary so they can be compared one to another.

Blindness as a Result

The dog’s retina consists of thin layer of tissue that is located behind the dog’s eyeball. This structure is supplied with oxygen and nutrients though several small blood vessels.

When a dog’s blood pressure gets too high, these blood vessels burst and leak fluids along with blood into the eye. As the pressure increases, the fluids and blood accumulate which causes the retina to lift away and detach. The more the retina is detached, the greater the vision loss.

In dogs, therefore, blindness tends to occur as a result of a high systolic pressure. The loss of vision tends to occur suddenly (within hours or days) and the affected dog will often have dilated pupils regardless of light conditions and there may be red blood seen in front of the eye (hyphema). Owners often report seeing their dog bumping into objects or having difficulty seeing objects such as treats or toys.

The most important question dogs owners ask is: will my dog’s vision return if the blood pressure is lowered? The answer is, it depends. If the high blood pressure is corrected, and the underlying cause is addressed, there are chances that the vision may return, explains Dr. Rebecca.

Timing is of the essence though. It’s very important that the problem is addressed as soon as possible. Dog owners should see the vet at the first signs of trouble. If the retinal detachment is treated quickly and aggressively, reattachment may occur, and in these cases, it’s possible that some dogs will gain back their vision, points out, Dr. Rhea Morgan.




Several Underlying Problems

As mentioned, it’s important to investigate the underlying problem causing the high blood pressure to happen in the first place. While in humans, ninety percent of cases of high blood pressure are primary, in dogs and cats, secondary hypertension accounts for most cases, explains Mark Acierno, a board-certified veterinarian specializing in internal medicine.

What conditions are known to cause high blood pressure in dogs? There are several. High blood pressure in dogs  may be caused by acute or chronic kidney disease, liver disease, protein-losing nephropathies, Cushing’s disease, diabetes, hypothyroidism or heart disorders. Sometimes medications may be to blame. Medications known for causing high blood pressure in dogs include erythropoietin and phenylpropanolamine.

Did you know? According to a survey(Cowgill, UCD) 73 percent of dogs suffering from kidney disease had elevations in their blood pressure.

 

At the Vet’s Office

If your dog has undergone vision changes or blindness, your vet will likely examine the eye carefully with an opthalmoscope. It is possible for the veterinarian to identify detached retinas or retinal hemorrhages this way. Your vet may also run several other eye exams.

Blood work and urinalysis can turn helpful in determining the presence of an underlying disorder triggering the high blood pressure

Your vet may take a blood pressure reading and will suggest medications to lower it. Fortunately, there are several medications that can be used to lower high blood pressure in dogs. The most commonly used include enalapril, benazepril, atenolol, metoprolol and spironolactone.

Eye drops may be prescribed to reduce inflammation of the eye, and if there is retinal detachment, the vet may prescribe steroids to be taken internally by mouth.

With lower blood pressure and less inflammation, there are chances that the collection of fluids and blood causing detachment are slowly reabsorbed and the retina may reattach, and possibly restore some vision.

 

References:

  • LeBlanc NL, Stepien RL, Bentley E: Ocular lesions associated with systemic hypertension in dogs: 65 cases (20052007), J Am Vet Med Assoc 238:915, 2011.
  • Small Animal Practice Client Handouts, By Rhea V. Morgan, Saunders; Mac Win Pa edition (March 12, 2010)
  • Blue Pearl Vet:  Hypertensive Retinopathy
 


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