There is no side-effect to glasses, you can put them on or off completely at-will any moment, and they make a very exact correction to one specific parameter (vision focusing ability).
ADHD meds are imprecise and affect many systems in different ways - some positive and some negative. You can only have them on/off daily. It might affect you differently depending on other factors. And treatment is not without risk.
It’s hard to understand how stopping will affect you due to the imprecision. It’s not as black-and-white as glasses.