I can use my eyes to convey lots of expressions. I have very big eyes which are good for such things. Let me show you.
Here I am being alert and watchful. Notice how big my pupils are. They are like this when I am on high alert.
The next one is my slightly annoyed expression. I squinch my eyes together just a bit and have a serious look that lets Mom know that I am not in the mood to be photographed.