I find this thread fascinating, as I've been thinking about piano vision a lot. For those of us with progressive lenses, it gets even more complicated.
With octaves, e.g., the Liszt B minor sonata octave passages, I find it helpful to look solely at the thumbs, even if one is emphasizing the top note in the right hand (the fifth finger). In playing difficult chamber music, where I don't have the entire piece memorized but go back and forth from score to memory (e.g., Brahms D minor violin sonata), I have made giant pencil marks to train my (aging) eyes where to get back on track.
In general, when reading music, I try to force myself to look ahead a measure or two, to prepare my fingers and brain for what's coming. I find when I'm tired, I read the score right at the point I'm playing--generally not as good.
Cheers!