Chronic kidney disease commonly causes hypertension in dogs and cats. Other causes in cats include hyperthyroidism, a high sodium diet, and certain medications. Other causes in dogs include hyperadrenocorticism, adrenal gland tumors, kidney tumors, diabetes mellitus, elevated red blood cell counts (polycythemia), and hypothyroidism. Spontaneous hypertension can occur in dogs and cats, but this condition is rare. Our team at Veterinary Vision Center wants to explain how hypertension can affect your pet’s vision, and how these ocular issues are addressed.
What is hypertensive retinopathy in pets?
The retina is the eye’s innermost, light-sensitive tissue layer. Small blood vessels provide oxygen and nutrients to this thin material, but when systemic blood pressure increases above 180 mmHg (systolic) and 95 mmHg (diastolic), changes can occur in the vessels supporting the retina. The small conduits cannot accommodate the excessive pressure, and begin to leak fluid, and eventually burst. As the pressure increases, the larger vessels entering at the back of the eye are also affected. The released fluid accumulates under the retina, causing detachment from the oxygen and nutrient source.
What hypertensive retinopathy signs are seen in pets?
No signs may be seen if the hypertensive retinopathy is mild, and the condition may be noticed only when the pet is examined for another issue. In more severe cases, signs include decreased vision or acute blindness, enlarged pupils affecting one or both eyes, and blood inside the eye. The pet will also likely suffer from a concurrent disease, and have signs specific to that disease process. Specific signs are as follows:
- Kidney disease — Increased water intake, increased urination, decreased appetite, lethargy, vomiting, and diarrhea
- Hyperthyroidism — Weight loss, increased appetite, increased water intake, increased urination, and an unkempt hair coat appearance
- Hyperadrenocorticism — Increased water intake, increased urination, increased appetite, lethargy, thin and fragile skin, hair loss, and a potbelly appearance
- Diabetes mellitus — Weight loss, decreased appetite, cloudy eyes, and recurring infections
- Hypothyroidism — Weight gain, lethargy, hair loss, dull hair coat, cold intolerance, and recurring skin and ear infections
- Polycythemia — Difficulty breathing, lethargy, increased water intake, increased urination, nose bleeds, and seizures
How is hypertensive retinopathy diagnosed in pets?
Hypertensive retinopathy is diagnosed by thorough ophthalmic examination and blood pressure evaluation. Abnormalities seen on the ophthalmic exam in mild cases include small, circular lesions in varying numbers along the back of the eye and increased vasculature. As the disease progresses, hemorrhaging will be seen along the back of the eye, followed by retinal detachment. In cases where blood fills the eye, ultrasound can be used to assess the ocular structures. Blood pressure of pets is measured similarly to humans, but special equipment, such as a doppler probe or an oscillometric machine, are required to detect blood flow in the pet’s tiny veins. Blood pressure should be measured several times to obtain an accurate reading.
Once hypertensive retinopathy is verified, other diagnostics will be performed to determine the underlying cause behind the condition. These tests may include bloodwork, X-rays, ultrasound, and an echocardiogram.
How is hypertensive retinopathy treated in pets?
The underlying cause that initiated the hypertension will need addressing, so determining this factor is key for successful treatment. Antihypertensive medications can be administered to help bring the pet’s blood pressure down to a normal level. To address the eye abnormalities, the pupils are typically dilated to prevent the pupil becoming scarred. Topical steroids are also used to help decrease inflammation.
Referral to correct the detached retina is important to salvage the pet’s vision. Treatment will be focused on medical therapy to promote subretinal fluid resorption and, if necessary, retinopexy (i.e., mechanical retina reattachment). Systemic steroids and diuretics are used to help resorb the fluid under the retina. These medications can be damaging to pets suffering from certain disease processes, so these issues must be considered, although most cases respond well to medical treatment alone. Retinopexy involves using cryotherapy or laser treatment to form adhesions between the retina and underlying tissue.
What is the prognosis for pets with hypertensive retinopathy?
A pet’s overall prognosis depends on the underlying cause behind the hypertension, and their treatment response. Pets who receive prompt correction of the ocular changes often recover their vision in full, although signs may not fully resolve for several weeks to months. Ophthalmic exams and blood pressure measurements are often repeated every seven days until ocular signs improve and the blood pressure remains normal. Pets will require lifelong ophthalmic monitoring to ensure the retinal problems are controlled, and their blood pressure must be closely tracked.
Hypertension is a dangerous condition for dogs and cats, and should be addressed as promptly as possible to help save their vision and their life. If you are concerned your pet may be suffering from hypertensive retinopathy, do not hesitate to contact our team at Veterinary Vision Center to schedule an appointment.