Hypertensive retinopathy is a condition where high systemic blood pressure (hypertension) causes secondary retinal detachments or retinal haemorrhages. The problem tends to occur most frequently in elderly cats, and results in sudden blindness.
The retina normally lies flat against the back of the eye and contains cells (called rods and cones) which detect light, converting light stimuli into electrical impulses which are then transmitted to the brain for visual processing. When the retinas detach from their normal position, they cease to function and the patient becomes blind. Although immediate reattachment of the retinas can sometimes restore vision, cats' retinas degenerate quickly (hours to days) so in many cases by the time the diagnosis is made, the prognosis for vision is poor. Often retinal haemorrhages i.e. bleeding from small blood vessels in the retina can occur as well.
Since the hypertension caused the retinas to detach, treatment and control of the hypertension can help to achieve at least partial reattachment of the retinas. Unlike humans, high blood pressure in cats and dogs is not caused by poor diet. Instead, hypertension in animals is usually secondary to another problem such as kidney disease, heart disease, cushing's disease or thyroid disease. Treatment for hypertensive retinopathy usually involves an investigation into the possible underlying diseases responsible for the hypertension. Most commonly a drug called Amlodipine is used to control the high blood pressure.