Vet doesn't know why my cat is going back and forth between blind and seeing

This is an update on a previous question. My 22-yr-old neutered male DSH has been going between blind and seeing for about six months now. His pupils go between normal narrow to fully dilated, and I can watch them go all the way back and forth within one second; other times they are steady. The vet checked BP and that wasn't it. Sometimes he walks round and bumps his head over and over, and paws the air when wanting to jump up. Other times he reacts to something moving ten feet away. I keep testing him over and over. And sometimes his pupils are normal and he still can't see. The vet has no idea at this point. Is this anything recognizable? At his age I won't spend money on expensive tests, but I am super curious and really wish I could help him.

I am so sorry!   Have have reread this and would like to apologise for the obvious error in my post!!!!     As a matter of fact, the age of the patient changes nothing in this case ( I got confused by a previous post), but allow me to do full justice to your patient!

It sounds as though your poor old cat, as well as being rudely misaligned by this vet, is in a difficult position.   I don't think that the species changes what I am going to say in this case, but is still important to get right.   He sounds to be confused and stressed by these incidents, which could indeed be related to blood pressure (if it is, it is a difficult thing to detect because most cats blood pressure might be high while they are blind, and perhaps revert back to normal when they could see, for example).  I wonder whether the ocular pressure is increased at these times?

Either way, it sounds as though specialist measures or knowledge or both, may be needed in order to find out what is going on.   It is always okay not to find out, as long as your cat is not in pain or distressed and you can accept that not understanding the cause may mean that chances to intervene may be being missed.  I can see why you might make this decision for an elderly home loving cat.   However, it sounds to me as though your cat may be distressed - for short periods of time at least - which suggests that you need to constantly review the patient's welfare as well.    This is obviously an extremely difficult dilemma and we would be interested to hear how you resolve it.

With my utter apologies again for my insensitive mistake at the top.

Gosh, no worries, didn't even see anything insensitive : ))  I appreciate the advice, and think I will do as you suggest, and just continue to care for him, which I love doing. I do have, however, a new question, but it's possible they are somehow connected. My cat lost his sense of smell completely about two years ago, I have had to train him that the stuff he's bumping into is food, and to put out his tongue to taste it, then he figures it out. He's shown zero signs of sense of smell all this time. Now this past week, this absolutely absurd cat is eagerly sniffing my roommate and me all over when we come in the house, although we're both just going the same places as all along, no new people or dogs or anything. He may just be doing it to mess with me; that seems more likely than getting smell back? ... how can this be? and is it a symptom of anything? boy am I bewildered!