I couldn't manage to convince my parents that I had piss poor vision until I was 8 years old. When I finally managed to get them to take me to the eye doctor and get prescription glasses, my mom apologized to me repeatedly for like 2 weeks.
I never even knew that I actually had bad vision until that first prescription at age age 8. If you've never seen clearly before, you don't even realize your vision is blurry to even tell anyone.
But you'd figure that they might have started getting a clue years earlier when I got lost in my own room, couldn't see the chalkboard in class, and had to sit super close to the TV..
My dad would get mad at me for sitting too close to the tv or for not recognizing people. They never thought to have my eyes checked until my Kindergarten teacher had the school test my eye sight