Preventing Sudden Blindness in Cats – Check Blood (not eye) Pressure
Retinal Hemorrhage and Detachment
Should your clinic routinely check blood pressure in cats over 12 years of age?
Systemic hypertension is common in older cats and is a leading cause of feline vision loss. Sustained undetected high blood pressure leads to damage, leakage and rupture of blood vessels in vascular intraocular structures such as the iris and chorioretina. With the iris this can manifest as ‘bruises’, or large anterior chamber blood clots blocking vision, the latter being easier to detect and more obvious to owners. With the chorioretina, blood vessel leakage and rupture can lead to exudative retinal detachments and retinal haemorrhages, leading to vision loss. If detached and deprived of normal nutrition for too long the retina will suffer permanent damage leading to irreversible blindness.
Anterior Chamber Hemorrhages
Most cases of high blood pressure in cats appear to be age-related and primary without an underlying cause. There is almost invariably some accompanying renal disease, which is usually the result of high blood pressure, but sometimes primary renal disease can be the initiating cause of the high blood pressure. Hyperthyroidism and other systemic causes of secondary systemic hypertension should also be ruled out with blood tests. Regardless of the cause, oral amlodipine given once daily is the initial anti-hypertensive of choice, starting at 1.25mg per cat. Any primary triggering disease such as hyperthyroidism will require additional specific treatment. The prognosis for vision is guarded but prompt diagnosis and ongoing appropriate anti-hypertensive treatment gives the best chance of haemorrhages clearing, retinas reattaching and some vision returning.
Early detection and treatment of hypertension may reduce the incidence and severity of vision loss.
