I also recommend an onscreen magnifier that appears and disappears on hotkeys. I use MacOS' built-in one, set up to show when ctrl-alt are held. I have only moderate myopia, but the magnifier makes it much more comfortable to look at small-ish things on the screen. There's an image that you wish was bigger? No need to open it separately or bend forward—just mash the keys, bam, it's half the screen now.

On the non-hidpi screen the magnifier pretty much took me to the days of 800x600 screens, causing frequent reflections on how the times change. But on hidpi, it's more like I get a 1280x800 screen in the magnifier. Works like magic for images with small details, e.g. aerial photos: almost like peeking through a telescope.

Yes I do this too, for exactly the same reasons. Also makes me feel like a grandpa, but who cares. Also it makes me realize how frequently apps fail to account for large system-level font sizes.

It's possible that the brief headache is due to confusion between vergence and focus. I.e., your brain is going "my eyes are converging a point 30cm away, so why am I focusing as though it's infinitely far off?!"

If this is the case, adding base-out prism to the lenses could (in theory) solve problem.

https://www.eophtha.com/posts/fun-with-prisms-in-ophthalmolo...

I did this not for eye strain but so I would stop craning my neck forward, and it works fantastic.

I just put 2x scaling on all the screens (all 4k+, so do what works for your screens),

I’d say from there I slightly scale down most websites using the browser to 90% or 80%.

Have you compared similar font sizes on different monitors? I’ve realized monitor quality makes a big difference when reading text for hours on end. Some produce very sharp text, others not so much.

All retina monitors have had impeccable text sharpness since 2012. However, for desktop monitor sizes anything less than 5k isn't acceptable.

Do you wear glasses often, given that you have 20/20 vision?

No, my eye doctor actually just prescribed me a set only for looking at screens because it increased the sharpness (apparently one of my eyes has stronger visual acuity than the other, and this imbalance is exacerbated when staring at screens but also I was told this is pretty common). I spent a lot of time trying to "hack" a solution for my eye strain and constant headaches, so I tried a bunch of things, including readers.