New concept for ranking your closeup intensity

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)


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.

Interesting idea. I have tried it out, and as I work at a normal laptop computer screen at a distance of 60 - 65 cm without any correction, the ranking puts me very close to the actual time spent in front of it without a break. 30 minutes puts me at 30.5 (if I have done the calculation correctly). For book reading it would be about half of that as I hold the book closer. I do not use any small screen. Do you then just add up the total time spent in close-up vision during a day? I am not sure what you mean by full recovery. Would getting up to put wood on the fire, cooking a meal, or doing the dishes count as full recovery? I don’t consider any of these as requiring close-up vision and all require regular shifts in focal distance (and I do all without correction). It is very rare that I would work at the screen for 30 mins without a break, but I cannot say the same for a really gripping novel. :smile:

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I threw in the term for how many diopters being worn (regardless of myopia level) more to get at the strain due to extra convergence from the lenses. That’s also why closeup distance is weighted so highly.

You all can keep trying this out and we will see how well it works over a range of conditions.

@Ursa, you need to use your judgement of what constitutes a full recovery from closeup.

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On second thoughts, there should be a cut-off at very short periods of close-up, where these would not add anything to your total daily close-up time, as this would be a ‘normal’ close-up use of one’s eyes. An example of this would be just checking your inbox to see if there are any new emails. I do this several times a day, and if there is nothing new to read or reply to, it is a matter of half a minute.
Edit: should there not be a weighting for the length of time you spend without recovery, e.g. 1 hour would be weighted more than 20 minutes. This could be done by adding a fixed fraction of T to T, e.g. T + .25 x T.

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You also need a term for the amount of time spent operating the formula :crazy_face:


love the idea of the formula but sorry I couldn’t resist being a smart ass, you realise that constant variable is an oxymoron right haha

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Yes, it was fun, but I won’t be doing this very often.

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How about Discrete variable? Or “variable constant”.

:slight_smile: Maybe Hannie’s link has a point. I just mean that in programming it’s either a variable or a constant, but everyone knows what you mean was just playing around

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