When I was younger, my ophthalmologist was still testing for depth perception through binocular disparity (the parallax effect, I think). I could pass those tests (although my mother is in the 20% or so of the population that can't do it), but I never could see those stereoscopic images for some reason.

I haven't been tested for many years, but I assume I have lost this type of depth perceptiion due to monovision after cataract surgery. I still have functional depth perception, but it must rely on other clues these days. And I still can't see stereoscopic images.

At least there are tools now that can undo the process by which these images are produced.