Eye issue

Today I noticed my Ambilobe Panther Chameleon, Monster (unofficial name), has developed some sort of eye problem. His left eye was closed all day he only opened it once in front of me and I did not see any noticeable damage. With that being said, he ate two crickets, however, he did not move around the cage as much as he usually does which concerns me. I've been thinking of reasons as to how he could have developed this problem and my conclusion as of right now is, I used my vacuum cleaner in my room yesterday and it is possible that he got a piece of dust in his eye. I hope with some misting and some eye rolling on his part, he can get through this and it's nothing serious.