Cross your eyes together until the 2 images murge into one big blur, then try to focus your eyes so you get a clear central image. Might take a few minutes to take the hang of; its a little bit of a strain on the eye muscles but not much.
Once you get the cross-eyed image, you can notice the differences immediately when you see a part of the image that appears to be flickering. That's your brain interpreting something that appears to be there in one image but doesn't in the other image, and trying to make a composite image of the info.
For the little/small details and differences, its easier to uncross your eyes and look normally.
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