Loone
Bear
Relax your eyes, or squeeze. Now let ur eyes focus on on a specific point (to where you can still see the lines), and the message will appear. It also helps to put it on a black background for more contrast.
Creating some distance between you and the monitor also helps.
It is also unfair, because depending on how your brain works, you'll either see the message, or gibberish. It's the same with this:
Either you see a young beautiful woman, or you see an old lady. It's the same principal with the cipher. You either see the message, or gibberish. Now, in this picture you are able to see both. But that is due to the fact that you know the picture beforehand, or is told that there are multiple perceptions.
I know this, still, I find it hard to actually recognize something inbetween the lines.