Opthamologist scans used to overlay an image to approximate how I see the world and how a person with normal vision would.
If you could imagine a crowded place you would see everyone heads and shoulders. I'm lucky to see one.
The image shows a couple of roos. You'd notice them all quite quickly, I'd take awhile to notice the one front and centre and most likely would never be aware of the second one unless you pointed it out to me.