As I mentioned several days ago I’ve been seeing if a dark theme in VS would help my eyes a little. The short of it is – no, no it didn’t. The major sore point is that if you use a dark theme in VS then you find yourself constantly swapping between dark (VS) and light (web content, content in general). The latter of course doesn’t sound like its particularly good for you and I’d definitely concur with that.
I actually found that my background was slightly off-white in my VS settings and since changing it to pure white around 3 or so days ago I’ve found that my eye strain has just disappeared. Funny thing is I can never remember changing the background colour.
I’ve no doubt that the colour schemes used in VS are very subjective so I won’t announce that light themes are the best, but it seems to work well for me.