Diagnosis

Clinical signs of hypertensive retinopathy can be unilateral but are typically bilateral. Presenting complaints include blindness, vision loss, or progressively dilated pupils. Hypertensive retinopathy also may have a subclinical presentation, noted only during routine examination of the fundus or during examination of cats with high blood pressure or those evaluated for a gallop sound or heart murmur. Serous retinal detachment often can be diagnosed with a penlight from arm’s distance. Retroillumination of the eye is achieved by holding a light at arm’s length from the patient. A normal eye should show bright yellow-green tapetal reflection in the pupil, although a blue eye may have a red pupil due to a lack of tapetum. Retinal detachment results in a dampening of that reflection caused by the presence of fluid between the retina and the tapetum. The proximity of the retina to the lens also sometimes allows the retinal vessels to be seen directly through the pupil. Retinal examination is difficult with retinal detachment, and the entire fundus may seem blurry. Focal areas of detachment are blurry and hyporeflective and are sometimes associated with hemorrhage beneath, within, or above the retina. Hyphema or vitreal hemorrhage also may be observed.

Treatment and Prognosis

Treatment of hypertensive retinopathy is focused solely on control of the systemic hypertension. No topical medications are indicated to treat the ocular component. Amlodipine has been demonstrated to be particularly effective in the resolution of systemic hypertension and hypertensive retinopathy (Maggio et al, 2000). Current recommendations for the treatment of systemic hypertension can be found in Chapter 169, but cats with hypertensive retinopathy should be evaluated for underlying systemic disease, including renal failure, hyperthyroidism, and the more uncommon condition of hyperaldosteronism (Conn’s syndrome).

The prognosis for vision varies depending on the duration of the retinal detachment, with experimental models showing a return to function if the retina has been detached for 2 weeks or less. Unfortunately, because of cats’ ability to adjust to vision loss, the retina typically is detached long before the patient is seen by a clinician. Although resolution of the hypertension usually results in reattachment of the retina, continued retinal degeneration is likely to occur. Thus some cats who are visual at presentation or regain vision immediately after treatment may continue to go blind despite adequate control of blood pressure.