My cat had an eye removed to years ago. Since last July, we’ve noticed that he’s…

I am sorry to hear about your cat. One of my first concerns in a cat with acute blindness is high blood pressure. If a cat's blood pressure gets too high, the back of their eye can unattach and blindness occurs. A blood pressure can be easily checked and then treated if needed. I would also be concerned about glaucoma (an increased pressure) in the eye. While more unusual in cats, it could also cause blindness. The good news is it is also easy to test for and can be treated as well. If these all look good, a brain tumor is on the short list of possibilities, depending on your cat's age and other symptoms. The hard part is the diagnosis for this is usually done by CT scan or MRI. I would also throw out there that some brain tumors are treated fairly easily by surgery. Hope this helps and good luck with this.