[Aachen]

First time I hear someone describe nausea from dark mode. Quickly looked astigmatism up on Wikipedia - isn't that something glasses fully correct? I think I've got this as well, but not sure, I've just always had glasses and take whatever they measure to be the best possible lens

(Of course I critically evaluate the measurement, like one time I actually couldn't read faraway text with what they were proposing whereas I could with my old glasses. But I don't know the exact values or terms for the different defects, I think my eyes have at least three different issues including something about rotation as astigmatism apparently means)

I guess what I'm asking is why you don't have glasses. Are they too expensive in your area, or the defect only very minor so it doesn't impede safety when driving even on highways? (Then I'm surprised you get nauseous though, since I don't when I read anything without glasses, regardless of dark or light mode.) Or if you do have glasses, is this still an issue while wearing them? If so, any idea why?

[giingyui]

I have glasses. They greatly ameliorate the issue, but not completely. My prescription is a single number which I don’t believe has the necessary granularity (I think, intervals of 0.25) to express the exact prescription I need. I also suspect that astigmatism is a deformation of parts of the eye that cannot be expressed with a single number. It’s possible I should have gone to an ophthalmologist instead of an optician in a mall but that’s what I did.

Also I generally don’t wear the glasses unless I’m working (with a computer of course) or driving. I also have myopia, but both my astigmatism and my myopia are mild. The problem is much more severe when it’s dark, so I always wear my glasses when it’s dark and I very rarely wear them during the day. I must always wear them if I intend to use the computer for a long time, though. Especially if I’m staring at a terminal or whatever else with white letters on a black background. But I don’t need them to read (black on white, not too far away) or to use my mobile (always closer to my face than my monitor).

Judging the distance/speed of other cars during the night without glasses is simply impossible despite my mild prescription.

[Aachen]

This is very interesting, thanks for sharing details. A friend with strong corrections in their glasses always mentions they feel like they can't see much in the dark, not as much as other people anyway, but we've never been able to quantify it (that they don't see something that I do). That you always wear them in the dark sounds to me like it's indeed more important to correct this effect for dark backgrounds, which I had no idea about

Another comment I saw in the meantime, https://news.ycombinator.com/item?id=44520306, proposes a mechanism for why one might have what I'd call ghosting if it were a computer screen (apparently it's called halation for eyes). That that can lead to nausea or generally feeling like things swim together and you can't see as well makes sense, this might explain a lot

I'll mention this to the friend and maybe we can do some tests in the dark with moving objects rather than just "can you see that thing there". Maybe after all these years we can get to the bottom of this issue they've had all these years :D

[giingyui]

It’s not ghosting, it’s halation as that bloke said. Bright things do not leave a trail, instead they are just blurry.

If I see a white LED in the dark, the LED shows some sort of smear at a certain angle and with a certain length. The length of the smear decreases the closer I get to the LED. It doesn’t change ever, even if days pass, because it’s a static deformation inside my eye. It does not leave a trail if I look around or if I move the object with the LED.

This also applies to white letters on a black screen. They are smeared at an angle. If I’m far away enough and/or the letters are small enough the smear is so large that they make it hard to read and make me nauseous. That’s why I ended up buying the glasses.

https://pixelbuddha.net/storage/51621/how-to-create-a-motion...

This is an example. The trail is not as long but it’s brighter. (Just googled “motion blur letters” - the effect is similar)

[Aachen]

Oh! I see, I guess the "then look at a bright surface" part of that other post made me think of that an image stays with you for a short time (a ghost image), but I get what you mean now