Here I propose a new concept for ranking your closeup intensity numerically. Here’s the beta release version of my closeup intensity calculator:

I = T x (1/D + 0.5 x S + 0.5 x E)

Where:

I = total closeup intensity

T= time in minutes engaged in near vision without full recovery

D= distance in cm

S= absolute value of negative spherical equivalent of glasses worn (drop the minus sign).

E= “Electronic”. This is a constant variable. E=0 for 3D objects. E=0.5 for printed material. E=2 for an LCD computer screen of normal size. E=4 for a smaller tablet screen. E=6 for a tiny phone screen, such as the original size iPhones or iPod touch models.

This is not a scientific thing, rather a ranking system I came up with, similar to the one doctors use to ask you to subjectively rank your pain from 1 to 10.