this might be a simpler way to just touch up images, without including seperate layers or anything. Just zoom up real close on the eyes, use the lasso select tool and draw a circle around the black part of the eye. Then with that selection, go to image, settings, color adjustments and reduce the amount of red in the selection. Then repeat with other eye. I've also used this to tone down blotchy red skin abrasions somewhat.
You can see what it looks like, anyways.