Many cats are living longer lives,
and unfortunately, are acquiring diseases that were not seen as
commonly in the recent past. Hypertension (high blood pressure) is
one of these diseases. This increase in blood pressure affects many
organs, particularly the eyes, kidneys, and heart.
The primary symptom most owners notice is a sudden onset of blindness, as evidenced by dilated pupils and bumping into objects. Cats that were apparently fine just a day or two earlier are now completely blind. Prior to the onset of blindness an owner might notice other symptoms. These might include weight loss, excess drinking and urinating, vomiting, change in appetite (up or down) and fast heart rate.
Ollie is exhibiting all the classic signs of blindness. Both pupils are dilated and stay that way, even when a light is shined on them. In addition, his left eye shows signs of potential hemorrhage.
Feline hypertension is almost always secondary to other problems. The primary ones are hyperthyroidism and kidney failure. Any cat that has been diagnosed with one or both of these diseases should also be monitored for hypertension, so that blindness can be prevented.
Every beat of the heart sends a significant amount of blood to the kidneys. As cats age and their kidneys shrink they are unable to take this much blood at once. This causes back pressure to the arterial system and raises the blood pressure.
The increased level of thyroid hormone (thyroxine) in the blood stream causes the heart to increase its output of blood, leading to an increase in blood pressure.
Older cats that have racing heart rates and a pounding heart rate, along with blindness, give an indication of hypertension. Blood samples that are easily obtained, or pulsate in the syringe when obtained, are another indirect indication of hypertension. Hypertension is suspected in cats that have been diagnosed with kidney or heart disease along with hyperthyroidism.
An examination of the retina by an ophthalmologist will sometimes give an indication of hypertension. There might be areas of hemorrhage or even detachment of the retina. Every blind cat should be seen by an ophthalmologist to check for hypertension, along with other causes of blindness like FeLV, FIP, fungal infections, and Toxoplasmosis.
An important tool in the diagnosis of hypertension is a blood pressure monitor. Cat arteries are very small, and the usual method to detect hypertension in people is not accurate in cats. A special blood pressure unit called a Doppler is used. A cat with a systolic pressure over 160 mm Hg is considered hypertensive.
Underlying treatment of kidney disease, hyperthyroidism, or heart disease is sometimes all that is needed to prevent hypertension.
Blind cats need to be placed on a drug called Norvasc to rapidly lower the blood pressure. There is a chance of regaining sight with the use of this drug, especially if utilized as soon as blindness is noted.
The best treatment for hypertension and its associated blindness is prevention. Any cat diagnosed with kidney disease or hyperthyroidism should be monitored periodically for hypertension. This will allow diagnosis of the problem before it causes blindness.
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