I sat at my home desk and measured the max and min distance between my eyes and all parts of the screen. I then presented those measurements in my next eye appointment, and the optician (not sure of American terms) was very appreciative that he had specific values to work from. He then simulated text at the different distances, and adjusted my prescription to work correctly over that distance. I think it was 18 inches minimum, 30 inches maximum.

I got computer glasses from that, no special blue filtering or whatever, just set to give me the best view.