Reason(s) for cat's temper worsening?

My cat, Oreo, who we have had all his life is a very laid backed cat, he lets complete strangers hold him and pet him. But recently he developed a respiratory infection, we took him to the vet and got some antibiotics. that was a few weeks ago and he seems to gotten over the infection but his temper is bad, he waits by the food bowl for our other cat or dog then swats at them and hisses, he is not scratching them, mind you, only swatting them away. And when he comes across one of them laying around he will hiss at them and even push our other cat aside. He is normally not like this, he use to be very chill with the other animals. Another detail is that we believe he might be losing his sight, he's an outdoor cat and he is approaching the age of 9. We have a vet appointment on Friday but I was wondering if any one had an idea of whats wrong with him in the mean time.

Asked by Member 1117967 on Jun 28th 2012 Tagged behavior, temper, infection in Aggression