Virtual Library | Hypertension and the Eye

You or someone you know may have hypertension, also known as high blood pressure. But did you know that dogs and cats can be diagnosed with this condition too? Systemic hypertension primarily affects the vascular tissue within the eye, including the iris, ciliary body, choroid and retina. Hypertension can also affect the cornea (intrastromal hemorrhage) when blood vessels have grown into the cornea for other reasons. Read on to learn more about underlying conditions, symptoms and treatment options for hypertension.

← Flip through our digital brochure

Systemic hypertension, or high blood pressure, can occur in both dogs and cats. It happens when there is persistent elevation in one or all blood pressure parameters (systolic/diastolic/ mean), affecting how much the heart has to work to move blood throughout the body. 

When hypertension occurs without a known cause, it is referred to as primary hypertension. When it is associated with an underlying disease that can cause hypertension, it is referred to as secondary hypertension. Typically, our furry friends get secondary hypertension rather than primary.

Similar to people, dogs and cats have a normal range for their blood pressure measurements. This normal range for systolic blood pressure is between 120mmHg to 160mmHg. Doctors like their human patients to have a blood pressure around 120mmHg (systolic)/80mmHg (diastolic). This would also be ideal for our four-legged companions. We give them a little buffer, however, because it can be stressful for some pets to be in a clinical setting. 

At our practice, we make it as comfortable as we can for our patients. Instead of using a stethoscope to listen for the pulses we use a special Doppler probe to amplify the sound.

With animals, high blood pressure is more often a secondary change that occurs because of another disease. In dogs, secondary hypertension is a common complication of renal disease, hyperadrenocorticism (Cushing’s disease), diabetes mellitus, pheochromocytoma, and hypothyroidism, among other less common endocrine diseases. 

Cats are a little different from their canine companions. Older cats, above the age of 11 years old, are commonly diagnosed with systemic hypertension. Cats with chronic renal failure and hyperthyroidism are particularly at risk for developing hypertension. Other conditions that can result in hypertension in cats include diabetes mellitus, chronic anemia, heart disease (hypertrophic cardiomyopathy), high-salt diet, and other endocrine diseases. 

If your pet was diagnosed with any of these conditions, monitoring for the development of high blood pressure is strongly recommended.

Systemic hypertension primarily affects the vascular tissue within the eye, including the iris, ciliary body, choroid and retina. Hypertension can also affect the cornea (intrastromal hemorrhage) when blood vessels have grown into the cornea for other reasons.

Treating high blood pressure requires your pet to start oral antihypertensive medications to help bring their blood pressure within the normal range. Often, these medications will be taken life-long. They are needed to help prevent damage to target organs, such as the eyes, kidneys, brain, and heart. 

If your pet experiences changes to their eyes due to high blood pressure, we may recommend specific therapies for the eye(s) to help preserve their vision and comfort. This can include eye drops or ointments, as well as other oral medications to reduce inflammation.

Hypertension can be a result of other diseases, therefore it is important for your dog or cat to undergo diagnostic tests to determine if there is an underlying cause. This can include a blood cell count, chemistry panel and a urinalysis to evaluate your pet’s organ function. Your veterinarian may propose additional tests, depending on other problems your pet may be experiencing. If an underlying cause is found, treatment for the cause may be recommended along with antihypertensive therapy.

To ensure your pet’s blood pressure is controlled, regular measurements should be performed with a veterinarian.

The clinical signs of hypertension can be variable, and depend on the specific component of the eye that is affected. Hypertension commonly causes hemorrhage within the eye. This is more obvious if it occurs in the front of the eye (hyphema), but it can also occur in the back of the eye (vitreous or retina). Sometimes the only outward evidence of hypertension is the presence of dilated pupils and/or decline in vision. Retinal detachments are a result of leaky blood vessels causing fluid or hemorrhage to build up under the retina.

If your pet has a sudden change in their vision, it may be due to one of the above conditions. It’s important to note that changes caused by systemic hypertension can be severe and lead to blindness if untreated. If high blood pressure can be controlled before severe ocular changes occur, the pet’s vision can be spared.