But then visual acuity isn't the limit when it comes to noticing the effects of a pixel grid, especially when typical content on a computer screen is mostly vector or pixel based rather than photographic.The viewing distance calculator mentioned in my original post above has a downlodable Excel file version which allows you to change visual acuity - the difference seems to be close to linear though, so 20/15 visual acuity should result in a ~34% increase of the optimal distance (or proportional decrease of diagonal size/pixel pitch).
http://carltonbale.com/home-theater/home-theater-calculator/
http://filmicworlds.com/blog/no-its-not-a-retina-display/