For me the constant side-to-side, combined with mouse usage was the problem. Trying to re-orient my field of vision (I wear glasses with a strong prescription a

For me the constant side-to-side, combined with mouse usage was the problem. Trying to re-orient my field of vision (I wear glasses with a strong prescription as well). Looking down or straight ahead has never caused me problems. I should also point out that on the train, I have a table where I sit (not in my lap, that sucks). I also try to use a stand-up desk more for all-day laptop usage.