We see with our minds, not really our eyes. The eyes are just receivers, not interpreters. That's the basis of Oliver Sacks's The Mind's Eye. People with apparently normal eyes who do not see (or stop seeing) the world as the rest of us do. A concert pianist suddenly becomes unable to sight-read music during a concert, a man's morning newspaper appears to be written in a foreign alphabet - neurological oddities appearing through vision and changing the lives of the patients. Sacks doesn't explain how these oddities happen (there is no explanation), but describes how the two, and a woman left aphasic by a stroke, compensate for their defects with varying degrees of success. They demonstrate the plasticity of the brain.
Stereo Sue's story is odder. We're used to people losing an ability and then coping, but Sue grew up with no depth perception. In her 50s, she began to see depth - not well or consistently at first, but eventually she developed consistent stereo vision. You don't miss what you never knew, and Sue had been satisfied with the flattened universe in which she lived. Seeing bioluminescent plankton in 3-D for the first time, though, she realized what she'd missed.
I've read most of Sacks's books, and they've become more personal in the last decade. One long chapter detailed his treatment for optical cancer and the related complications - a chapter which I skimmed, thanks to my extreme squeamishness about anything to do with the eye. He also discusses his prosopagnosia - face blindness. It's severe enough that he doesn't always recognize reflections of himself, but until a discussion with his brother (also face blind), it was his "normal" and not something he missed. Sacks then discussed his total lack of a sense of direction, and hypothesized that the two might be related.
That's when I stopped feeling like a ditz. My sense of direction is legendarily bad. Friends joked about it two years before I was even old enough to drive - and my mom jokes that even watching The Amazing Race on TV could be dangerous for me. I get lost in office buildings and disoriented in malls that bend. When I went to a friend's mother's funeral (coincidentally the day before I started reading The Mind's Eye), my mother got up at 6 am on a Sunday to act as my navigator, because otherwise I wouldn't find Long Island let alone the funeral parlor. I'm also not very good putting names to faces - I recognize people by their gait or voice, but when a fellow commuter greets me in the supermarket, it takes me a bit to realize I know them. I've spent decades thinking I'm inattentive or just an airhead, but instead, I'm probably miswired. In an odd way, it's comforting to know that, and it even allowed me to relax a bit on my latest road trip - with my mom, of course, as navigator.