Mathematical Language Precision

The fact that myope lenses are denoted with negative signs makes for all sorts of confusion in mathematical language. I’m a computer programmer, we tend to be very literal, especially about our math, and one always has to double-check with the client when dealing with special rules for negative numbers because different people mean different things.

Reducing negative sphere power is the opposite of reducing sphere diopters.

“I’m reducing my lenses” around here usually means adding not subtracting diopters. 90% of the time when we’re discussing simple cases, that language doesn’t matter, you’ll find out real quick your mistake if you accidentally order plus lenses instead of minus ones, and if all the numbers are negative, and there’s no multiplication, they act correctly. But when we get to cylinder described as plus, or last diopter issues, where there are mixed signs, it gets very confusing.

Then there’s “progression” which can mean “myopia progression” (eyes getting more minus) or “I made progress” (eyes getting more plus). “improvement” would be “myopia remission”. But usually around here we mean “EndMyopia method progression”.

I don’t expect to change the language used, the mathematically correct terms are confusing to most folk. Just venting a little bit.


I read “reducing lenses” as “reducing absolute spherical equivalent power of lenses used for a given distance.” That is almost always what people mean.

But the tendency to drop signs is driving me crazy. Especially when there’s minus cylinder and minus sphere and people drop one of the signs, instantly derailing the discussion into a “what’s even going on here” tangent that’s entirely fictional.

Don’t drop signs, folks. :face_with_monocle:


since the forum is called endmyopia, we have to assume we’re dealing with negative lenses, but “reduced” power/lenses always means towards 0, it doesn’t matter whether you’re coming from -4 or +4.

Disagree. look at my sentence above. reducing lens POWER means going towards 0 diopters. No confusion for me about that.
Increasing power always means higher absolute value of the diopter metric, regardless of sign.

if you are at low myopia and delving into plus lenses, as soon as you cross the threshold of zero, and add +0.25 or +0.5 you’re incresing the positive lens power again after having reduced the negative lens power. As long as reducing always means towards 0 and increasing always means away from 0 there is no confusion. I always just assumed it was like this for everyone.

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That’s exactly what I said.

Reducing negative sphere power is moving towards 0.
Reducing sphere diopters is subtracting diopters, which is going more negative.

still disagree with how you worded it. Reducing sphere diopters for me is ALSO going towards 0 i.e. both reducing sphere power and reducing diopters is for me going towards zero. To avoid confusion you should say INCREASING the negative diopters. then it is clear you’re going away from 0. if you word your sentences ambiguously then OF COURSE you introduce confusion.

I mean apart from you obviously who would say going from -6 to -8 is “reducing sphere diopters”???. I’d bet, not many people. they’d say increasing negative diopters

That’s exactly what I said.

Yup, an annoying convention leftover from Physics.

I’ve done a million of these problems during high school physics through rote memorization, and as soon as we passed the lens section it all went down the drain, left to be something googled if needed.

but who the hell uses the “mathematically correct term” when it’s obvious what is meant by reducing and increasing? If THAT is your main point, it’s irrelevant as it’s not a real life problem in my view

People who have to use them in other contexts.

Now, now, I too believe it’s a nonissue but there’s definitely value to keeping in mind language clarity. People familiar with the nomenclature will understand that reducing means approaching 0. But it definitely can get tricky if your gut instinct when you hear reducing is that it means more negative. There is definitely value in increasing clarity especially when communicating to those uninitiated with EndMyopia (which believe it or not does happen in real life). But of course the ambiguity is pretty short-lived as people realize that, an increase in magnitude (especially in the context of “illness”) is opposite of the desired result.

I understand where someone could make that mistake, such as the young-ones that are not that good with doing arithmetic involving signage, and it gets particularly tricky for reducing myopia if you’re trying to calculate the spherical equivalent of a reduction in plus cylinder. In which case, the rule is: if you’re removing plus cylinder, spherical goes more positive/2; if you’re removing negative cylinder, spherical goes more negative/2.
Otherwise, I think the mixup happens because the word “reducing” neither has a positive or negative direction, it has either a 1) downward or 2) downsizing direction as you go in the positive direction of time.
So like, 1) reducing cash means cash gets more negative (and potentially entering the debt realm).
But like, 2) reducing cash flow means cash flow approaches 0, whether it be positive or negative.

And in the context of diopters, it is something we (generally) want less of it regardless of its signage so it will be downsizing. Effectively meaning that reducing diopters will mean approaching 0 (cause we’re reducing the “bad” stuff).

people are thinking about it the wrong way if reducing is not clear.

Reducing the value of a metric is always making it smaller. Reducing a value in diopters is always going to mean making the lens less powerful and towards 0.

Anyone who thinks reducing a negative lens is making it more negative doesn’t understand what a diopter is. It could happen, sure but it’s like worrying that when you say “red” someone else will think “blue” (slightly exaggerated :smiley: )

If you meant in reference to diopters, yes. Because diopters is essentially a substitute-term for lens power, and anything moving away from 0 will be an increase in power.
Otherwise, no. I provided an example above when that is not true.
And I can provide another one.
You can reduce temperature which generally implies a smaller speed of molecules, but in terms of metrics, if you use F or C, the numbers go from positive => 0 => negative. So smaller=>0=>bigger.

Of course the examples are limited though, cause not too measurable things of life have meaning being negative.

right. Temperature is different. There going more negative is reducing. But so is a normal number. Let’s just say I was mainly talking about diopters.

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I’d probably argue that it’s perfectly simple as long as you stick to mathematical language. The problem comes from trying to translate it into English. (I wonder if all human languages have the same difficulty ?)

There’s also the detail that negative numbers are outside most people’s daily experience. (IIRC, even zero was a relatively recent invention/innovation/discovery.)

You write as if it’s entirely reasonable that, for temperature, it’s okay for “reduce” to always mean “more negative”, whereas for diopters it “obviously” means “towards zero”. You don’t find that odd/interesting ?

It is true that the choice of 0 is for a temperature scale is somewhat arbitrary - it is only when using kelvin that the magnitude of the number makes any sense, and eg that the ratio of two tempertures means anything.

For lenses, using 0 to describe the converging power of plain glass could also be argued to be an arbitrary defn. Over in another thread, I said that I choose to label the power of eye’s lens as 0 when at rest, even if it is in fact contributing some focusing power to the eye as a whole.

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looks like I’m outnumbered. whatever, for me it was obvious with diopters. if I’m in the minority, call it odd

Sorry, I genuinely meant “isn’t this an interesting phenomenon” rather than “look how inconsistent you are being”. I haven’t quite decided which side of the fence I’m on yet :wink:

Arbitrary yes, meaningless too, but it doesn’t necessarily not make sense.
For C, magnitude represents how far of a temperature you are from freezing water.
Similar sense for F.

Even among experts, there are issues where negative numbers are not handled well. Look for a consistent definition of “percent change” when dealing with negative numbers.

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BTW there is at least one temperature scale which was defined “backwards” - 0 was boiling point, and 100 was freezing point. So getting colder meant the number got bigger. Actually, ISTR the Celsius scale was originally defined this way round, then got reversed later.

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I for a living write programs that separate patients into categories:

  • PD - Progressive Disease (I’m sorry but you’re gonna die, just a matter of how fast)
  • SD - Stable Disease (Nothing much has changed)
  • PR - Partial Response (things are improving)
  • CR - Complete Response (looks like you’re cured)

Progression is bad news in my world.

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