How to conditionally format cells that look empty but are not actually empty?

Hi there!

First of all, thanks for reading my post.
Second of all, please consider that this post should've been named as: How to conditionally format cells that DON'T look empty. I realized about the mistake once I have submitted my post, so I cannot correct it now.

Here's my situation:

I have this formula on cell A1 on Sheet2:

=IF(Sheet1!A1="","",Sheet1!A1)

Then I drag the formula to the cells below on column A on Sheet2.
How can I set up a formula on the conditional formatting feature so as to highlight (say, for instance, color in yellow) ONLY those cells that DON'T look empty. If you take a look at my formula, chances are it will return nothing on some cells, depending on content from Sheet1. Yet, those cells wouldn't be empty; they still have content (a formula, on this case), so I can't use the condition =A1<>"" on the conditional formatting feature, because cells that appear as "empty" are not actually empty; so, eventually, all will be highlighted.