I am 47, and still prefer smaller fonts. Not because my vision is perfect! But it seems to have accommodated to looking at small fonts for last 25+ years. I wonder how rare / frequent it may be.
50 is about the age where you get presbyopia, ie. start to get difficulties focusing details due to loss of lens elasticity, circular muscle weakening, and makula degeneration.
Can confirm. I used to love tiny fonts for coding, for everything — more text, less scrolling! 10, maybe 11pt. But as I approached 50, I started bumping font sizes up. When one of my eyes actually started twitching, I gave in and got glasses. My 20 year-old self would shake his head at my 50 year-old self in his glasses, peering at his 15pt code.