> I asked my optometrist about the best setting for viewing comfort, and she said black letters on white background
I did some reading before I started using light themes, and the theory agrees with your optometrist, especially for astigmatism.
However, after getting an OLED screen, my experience didn't match the theory anymore: I could make the dark theme more comfortable with basic settings.
So I went back to check the research and I noticed it was not correctly controlling for ambient illumination and for the screen brightness.
I call that the 3 deltas:
- the 1st delta is between ambient brightness and the screen background color,
- the 2nd delta is between the screen background and the foreground color,
- the 3rd delta is between the ambient screen brightness and the screen foreground color.
In a dark room (at night), if you use a dark theme with a pitchblack background (as possible on an OLED screen) with a foreground of white text, it will NOT be comfortable if you leave the full brightness (usually 400 to 600 nits)
However, an OLED screen gives you precise control over the brightness: reduce it and you'll see it's possible to make the characters easier to distinguish on a dark theme than on a light theme.
I have scripts to do color inversion and different correction filters. I even have a shortcut for each, to reduce friction and try different settings for different conditions: I can go from a dark theme to a light theme in about 200ms, so I just go "click click click" on the keyboard until I find what conditions "clicks" with me :)
Unless I'm sitting in a very well light place (that I consider too bright for my preferences), I'm more often with the dark theme.
I'd encourage you to take into consideration the 3 deltas and try by yourself a dark theme while doing brightness control +- color filters, or at least to check the research (ask GPT!) your optometrist recommendation is based on.