Hypertensive Retinopathy

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION Once the diagnosis is established, further tests are needed Description to find the underlying cause of the hypertension, and these may Hypertensive retinopathy includes a number of ocular changes include routine laboratory tests, thyroid tests (cats), chest x-rays, that are produced by high blood pressure (systemic hypertension). and cortisol tests (dogs). Abdominal x-rays and an ultrasound may Systemic hypertension is defined as a systolic pressure greater also be recommended. An echocardiogram (heart ultrasound) is than 180 mm Hg or a diastolic pressure greater than 95 mm Hg. often done in animals with signs of heart failure or heart murmurs Most ocular abnormalities are associated with systolic blood pres- detected on the physical examination. Additional tests, such as sures greater than 200 mm Hg. (See also the handout on Systemic blood clotting tests, may be recommended to rule out other causes Hypertension .) of ocular bleeding. Ocular changes associated with hypertension include retinal hemorrhages, abnormalities in retinal vessels, retinal detach- TREATMENT AND FOLLOW-UP ment, and bleeding into the front chamber of the eye (hyphema). Treatment Options Multiple retinal hemorrhages are usually present and range in size from pinpoint to very large. The retina may detach in small, focal Goals of therapy include control of the hypertension, successful areas or completely. In most cases, several of these changes are treatment of the underlying cause, and improvement in the ocular present in the same eye. Both eyes are typically affected, but the changes. Antihypertensive drugs are started, such as amlodipine in abnormalities can be asymmetrical. cats and angiotensin-converting enzyme (ACE) inhibitors in dogs. Causes If possible, systolic blood pressure is reduced to less than 160 mm Chronic kidney disease is a common cause of hypertension in both Hg and diastolic pressure to less than 100 mm Hg. Appropriate dogs and cats. In cats, other causes include hyperthyroidism (elevated treatments for the underlying cause are also instituted. thyroid hormone), high-salt diets, and certain medications. In dogs, Hyphema usually causes inflammation in the eye, so topical other causes include hyperadrenocorticism (elevated cortisone hor- steroid (anti-inflammatory) drugs are often used. The pupil may mone), tumors of the adrenal gland and kidneys, diabetes mellitus be dilated with atropine so that it does not stick to the lens. If (sugar diabetes), hypothyroidism (low thyroid hormone), and elevated the retinas are detached, oral steroids may be considered, because red blood cell counts (polycythemia). Although it is rare, spontaneous topical medications applied to the eye do not reach the retina. Oral (primary, essential) hypertension may occur in dogs and cats. steroids must be used with caution, however, because they may aggravate uncontrolled hypertension and are contraindicated with Clinical Signs some of the underlying diseases that cause hypertension. Mild hypertensive retinopathy may cause no vision abnormalities or clinical signs and may only be discovered when the animal is Follow-up Care examined for other reasons. Severe retinal hemorrhages and com- Eye and physical examinations and blood pressure measurements plete retinal detachments lead to blindness. The blindness is often are commonly repeated every 7-14 days until blood pressures are sudden in onset (within hours to days) and may be accompanied normal and the ocular signs improve. The frequency of follow-up by dilated pupils. With hyphema, fresh red blood is seen in the visits depends on how well the ocular changes respond to therapy front of the eye. Other clinical signs of the underlying disease are and what is required to treat the underlying disease. Periodic mon- usually present. itoring is usually required for the life of the animal. Prognosis Diagnostic Tests If the hypertension can be controlled, most ocular abnormalities Diagnosis of hypertensive retinopathy depends on finding one improve and slowly resolve. It may take several weeks to months for or more of the ocular lesions in an animal with hypertension. hyphema to dissipate and retinal hemorrhages to fade. Abnormalities Hypertension is confirmed by repeated blood pressure measure- of the pupil may persist after hyphema, and retinal scarring is com- ments. Blood pressure is measured in dogs and cats with a blood mon in areas where hemorrhages occurred. If retinal detachments pressure cuff in a manner similar to that in people, but special equip- are diagnosed early and the hypertension is treated aggressively, ment must be used to detect blood flow in their tiny arteries. (See reattachment of the retina can occur. In these cases, it is possible for also the handout on Indirect Blood Pressure Measurement .) some dogs to regain vision, but most cats remain blind.