Personally I can't stand dark mode. It literally hurts my eyes. Strain after a few moments and interlacing ghost lines that linger in my vision for a minute. Does anyone else have this? Is it brain cancer?! edit: Thanks, I'm pretty sure it's not cancer. Question: But why me? Age? Staring too long at monitors? Drugs? It doesn't seem to effect too many others.
Similarly, this is why your eyes can hurt while reading in dimmer settings. It's not because low light itself is somehow harmful while reading, but because your eyes have a harder time staying focused as you naturally move while reading.
edit: I adopted light themes everywhere after reading this, probably https://ux.stackexchange.com/a/53268 . Knowing depth of field from photography helped this make sense, as well as understanding (from conversations with a doctor in my family) that the generic feeling "strain" is most likely associated with muscle activity than anything else.