Reduce when 1cm under your current subscription?

Hello everybody !

I heard a while ago, in a stunning podcast of The Shortsighted Podcast, a guy full of sense who had reduced really successfully : “reduce when 1cm under your current subscription”. I know we don’t have to take things literally and every path is one’s own, but still, I found it quite relevant.

That’s what I intended to do and what I have more or less done past reductions (done 2 reducs for now). But it has been three months since last reduction, time to reduce again, and I find I’m stuck to more or less 1cm under my previous prescription… That is to say, 31-32 L instead of what should be 34. Which seems a bit weird to me especially for my left eye which I’ve been doing patching with and which has worked quite well, it has improved.
I read also that indeed, improvement can be seen first on Snellen rather than on centimeter measurement.

What do you think ? Does this mean I should need a 4th month before reducing because eyes didn’t have the time to catch up, OR simply that my eyes cannot improve further with that current subscription, and that’s a sign it’s time to reduce ?

Do this “rule” apply to you usually ?

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The rule is flawed but the principle is good. I don’t think it’s necessary to be bang on in terms of measurements before you reduce. It’s too much perfectionism and extends the time spent on reductions unnecessarily, when you could be reducing and being more efficient.

The rule of 1cm is flawed just because of how diopters work: 10.5cm is -9.5, 11cm is -9 for instance. Whereas 50cm is -2 and 57cm is -1.75. It’s the way diopters work, fewer cm to change diopters the higher your myopia goes. A strict rule of 1cm, every time doesn’t work for all myopia.


How does the eye-chart look through your current glasses in good light compared with your “full correction”? If you’re reading 20/20 or 20/15 or better then it’s probably time to reduce again.

There are some subtle things that could be messing up the centimeter measurements to blur a little bit, like accommodation ratios. When your eyes are looking at something close they have to converge (roll inwards) on it, and converging triggers accommodation (focusing at near). There’s a “vergence accommodation” system and picking up something in your hand to look at it probably triggers it. You’re holding a tape measure in your hand, looking at a spot on a screen, the eyes are basically saying “Oh, we’re supposed to be in near mode now” when you’re really trying to measure is how far they can see in “far mode”.

If you’re not getting any (or very little) focus challenge because you’re seeing better than 20/25 or 20/20 it’s time to reduce again.

Just from what you’ve described I would at least order the reductions and see how they look. You might find they work great in nice lighting but in the evenings or bad lighting you still want to keep using your current glasses for a little while longer. It doesn’t sound like you’re “jumping the gun” to reduce again now.


Yes that’s totally true. I found it relevant as long as I’m in the -3s - beginning of -2s, as diopter ratio don’t change much. But reductions aren’t they supposed to last longer anyway going towards low myopia, because of this?

Thanks for this long answer and explanation. This sounds relevant :slight_smile:

Well indeed the eye chart looks really good, upper than 20/20.
Still, I find it really more difficult in the dawn and night - which you might tell me is normal for now, but I found that some weeks before it was clearer in the dark…

Also, this reduction is going to be only equalizing with one eye, so I won’t be able to put back precedent subscription to avoid messing with focal planes. This is going to handicap me a lot, especially for driving in the evening (which I’ll have to avoid for at least two months maybe). Even for people faces, I find it difficult when tired, if they are too far away, although the chart tells me everything is well. I find this weird. :woman_shrugging:t2: