I have a beautiful long haired tabby/ tortoiseshell cross 1 year old but her right eye pupil is wide open and does not dilate, the left eye is similar but not as bad, the vet finds this ‘strange’ but is obviously not familiar with the problem. Can anyone help please?
My Cat has Dilated Pupils – Hi Derek: I am not sure that you have described the problem accurately. If the pupil is wide open it is dilated it seems to me. Perhaps you mean that it does not change shape or narrow. The pupil is the opening in the center of the eye through which the light passes and which is narrowed or enlarged to control the amount of light entering the eye. The iris (a muscular structure) opens and closes the pupil. In the cat the pupil is slit like and the amount of light entering the eye can be further controlled by the eye half closing and going over the slit.
If the iris is not responding to different light levels by closing and opening the pupil that would indicate to me that your cat is blind i.e. light is not being received and no signal is being sent to the brain to regulate its impact on the retina. Blind or partially sighted cats can cope very well and therefore hide the problem.
Sudden blindness is often caused by Untreated Feline Hypertension. Early signs to watch for include dilated pupils which don’t respond to light. This is what is happening with your cat it seems to me. A low-sodium diet may be the answer but your vet can advise.
But this is perhaps a simplistic answer. Your vet should be fully aware of this. There is no substitute for a good vet providing advice on the spot.