In 1997 the majority of monitors were CRTs, so lines were naturally fuzzy and I think this is a large part of what causes eyestrain --- the inability to focus clearly. I remember upgrading to an LCD and the sharpness was amazing. I think widespread subpixel antialiasing later made things worse; when I first tried it, the text looked "too smooth" and I got dizzy, watery eyes because it felt like I constantly couldn't focus. Now I make it a habit of always turning it off, and I suspect the studies that say it increases reading speed are because for most people it subtly makes them want to not stop and focus --- it's subconsciously unpleasant to.