There have been some enquiries on this site concerning dilated pupils in cats. It is something that any cat owner can readily notice. The pupils can be wide open for a good reason, namely that the room is dark. Wide open pupils allow more light to impinge upon the retina.
However, if a cat’s pupils are wide open all the time despite variations in light levels and this has happened suddenly the cause may well be high blood pressure which has damaged the blood vessels of the retina causing a loss of sight which in turn causes the iris to fail to respond the the level of ambient light which leaves the pupils fixed and wide open.
High blood pressure or hypertension is common in older cats. The cat will also appear confused and disorientated. The retina may become detached. Permanent blindness will occur unless the retina re-attaches within a few days.
There is usually a specific cause for hypertension in cats such as hyperthyroidism or chronic kidney disease (the same as in humans). In humans it can be caused by being overweight, alcohol and high salt content in the diet.
As in humans drugs to lower blood pressure are administered. In humans, statins reduce blood pressure but the drug is used to control cholesterol levels.
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