It's not easy to help you without knowing a little about why you are asking. That's what we call 'context'. For example, are you having problems with your eyesight? The sentences seem to be saying the same thing, but why talk about what you can see if you shut one eye? Perhaps you are doing a grammar exercise and need to use the word either?
Anyway I suggest using 'if' or 'when' to make a more natural sentence, like this:
'If/when I shut/close one eye, I can still see out of the other.'