I’ve always been quite sensitive to bright screens and get headaches from eye strain too. Dark mode has made a huge difference to me.

I’m just happy that the mode switch is well supported across OSes and browsers nowadays, though it does add some complexity to theming web apps.

Staring at a bright light makes floaters visible, so dark is a must for me. Plus, code should never be dark-on-light, that's disgusting.

Astigmatism can cause eye strain headaches. I don't know if LASIK corrects that or not, or if you have it, but getting glasses with cylindrical correction helped reduce some of my headaches. Apparently most people don't see a big starburst around lights at night, or have a faint/fuzzy halo around text at any distance.