It seems most of us develop astigmatisms from using our screens less than an hour, particularly when at a 40 dev angle (like a laptop, phone) [1] and despite being temporary (mins, hours, days) the astigmatisms themselves vary in angles and wavelengths (read dark text, light text) effected from person to person. All of this adds up to no one person having the same level of strain from the same colors/brightness, and then compounded by it constantly changing and shifting with eye strain. For example, one of my eyes has trouble focusing on dark blue on bright white as the day progresses, the other eye hates red on black.