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.
