How can I tell if my Rat is blind?

Ok, so yesterday I was letting my rats roam around and I was noticing some strange behavior from my rat Baby girl. I'm not quite sure if she had noticed me or not. I would put my hand in front her face (I didn't do it aggressively) and she didn't seem to notice. But I couldn't tell if she had noticed or not because she didn't show any signs. So I did it to my other rat (who I am SURE she is not blind) and she did the same thing. Please, please, please answer my question. Thank you!