I somehow slipped through the UK eye-test system with -5 astigmatism until the age of 12.

I was 12 when I first saw a leaf on a tree.

I think I assumed everyone saw trees as they're commonly drawn and painted: as just a blob of green

That's funny, I didn't have nearly as bad eye sight, but also distinctly remember first noticing leaves on trees when I got my glasses around that same age.

I remember that first "OMG people can see things further than 20 feet away!?!" revelation.

Supremely curious: as a 12 y/o, did you assume everyone struggled getting around, always?

Yep!

I had an eyetest in primary school, I couldn't read anything. Looking back on it years later I assume she thought I was joking or else just royally cocked-up!

It left me with some strange cognitive coping strategies - like I would always dictate what the teacher was saying rather than reading it off the board.

The offshoot is I have very poorly formatted but fast handwriting!

wow the system really dropped the ball on this one

I failed high school algebra largely because I lost my glasses and was just trying to imagine in my head what the teacher was talking about. The adults in my life knew I had a prescription, and had the money to pay for them and yet nobody did anything. The bystander effect is truly bizarre.