Why not reduce a little CYL with each SPH?

I’ve seen recommendations to only make CYL reductions after 1-2 successful SPH reductions.

I’ve also read to “maybe” drop astigmatism all together if it’s very low (below 1 diopter). And I’ve read that 0.25 SPH can sometimes substitute 0.50 to 1.00 CYL.

Taking all this into account, I wondering why not reduce a little CYL with each SPH?

For example, here’s a hypothetical example of SPH and CYL:
1st prescription = -6.00 -2.00
2nd prescription = -5.75 -1.75
3rd prescription = -5.50 -1.50

I am not doubting the method. Years of trial and error are good enough for me to follow the advise. But I’m just wondering what usually happens when minor CYL reductions are combined with the 0.25 SPH reductions.


That might work, but your suggestions may be very case specific. It might workout for you, but not for others. It does sound like a plan to very slowly eliminate the astigmatism from the equation using only 0.25 increments.

It does sound like a plan, not sure if it’s been tried out successfully though.


I have wondered the same !

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It’s just a guess, but I feel that reducing both sphere and cylinder power at once could stress and overwhelm the brain, because you then have to clear some (myopic) blur and directional blur (astigmatism) at the same time. And it seems to me (those who have astigmatism, correct me if I’m wrong) that you do not always clear the two kind of blur exactly the same way, it can be slightly different (like it is between blur and the double vision you get at some point in the improvement process). So a double reduction could be too much, especially for the first reductions and even more if you’re still learning how to active focus correctly.

But that’s only my thought and like Laurens said, it might work for some people.


I agree with Sandra. From what I’ve learned, too many focal plane changes can be hard for the visual cortex. Multiple changes at once can cause dizziness, nausea, headaches, etc.
I would also think, like Sandra said, clearing up blur and astigmatic blur at the same time could be too much of a challenge, possibly slowing progress.


I do also have a gut feeling that it’ll be too much reduction at the same time. Then again, if you are at a solid 20/20 with your current normalized and this new reduction brings you to 20/40-50 it could very well work out. If these reductions are workable and you reduce them consistently like that, you should be okay. It’s trial and error though so we don’t really now until someone tries and reports on it.


The question here isn’t why not, it’s why?

In terms of benefit, the only one I can spot is having to pay for less glasses.

Reducing minus cylinder also reduces the average correction, adding to the blur challenge. Doing multiple changes at the same time will risk causing trouble by creating a bigger jump your visual system has to overcome all at once. If your eyes are able to improve more quickly, you should be able to get the same benefits from reducing lenses faster; there’s no need to reduce in larger steps.

So, as far as I can tell, this optimization only concerns money spent. It has no potential for improving the outcome.


0.25 sph plus the spherical equivalent of 0.25 cyl 0.12 makes only a reduction of 0.37 diopters. Sounds doable, but maybe not in the beginning. I wish I had taken that 0.25 cyl off in my 1st differentials, now I would soon have a pair for normalized I could test it with! Budget can be an important thing, because some people are facing 32-64 reductions/pairs of glasses.

I’m planning my next reduction, and my right eye is going to get EXACTLY that treatment. I can always bail out of it and go with a sphere/cylinder port/starboard going forward, but…I had quite a bit of improvement by just dropping all cylinder (and suffering with discomfort) for a few weeks.

Basically going:
OD: -2.25 -2.25x170 -> -2.00 -2.00x170
OS: -2.00 -1.75x180 -> -1.75 -1.75x180

I expect it will take me 4-6 weeks to adapt to the new lenses, and the subsequent one will equalize L/R to -1.75 -.175. If that strategy works for both rounds, I plan to step it down the same way until I can drop cylinder altogether…

BTW, I don’t get headaches, nausea, vertigo, etc.

I do get nauseated when I see a square turn into a vertical rectangle with one eye and a horizontal rectangle with the other. :slightly_smiling_face:


I also tried that on one of my reductions with great success. The astigmatism was noticeable but manageable. I did not do consecutive drops this way, but I will say that the astigmatism was slightly noticeable for about 2 drops afterwards. Which could present a problem, so watch out for that.

Good rule of thumb: I spend a full week of excellent outdoor emphasis to counteract any challenges that start to come up. This has helped sooo many times when I’m not getting the active focus I’m looking for. After that the active focus just continues happening much easier. But if after 1 week of outdoor emphasis you still feel the lens just aren’t working out, there’s no shame in backing up and slowing things down. Good luck!

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This is true! It’s why I went back up in cylinder mid-stream.

I’m looking forward to the next reductions coming Monday.

I’m a little apprehensive, because over the holidays I dropped back to the no cylinder lenses. I’m seeing almost perfectly with the left eye. The right still needs a little work.

I’m getting to a stage where I feel like walking it down will be doable.

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Very interesting concept. If someone has a high prescription and lots of overcorrection, I bet it would work. But otherwise, I think the reason people shy away from modifying both sphere and cyl at the same time, is because if you do that, you are reducing by a fairly substantial chunk all at once, which a lot of people have reported gave them trouble. It basically would mean that every 0.25 D sphere change and combined 0.25 cyl change has two components: an effectively 0.37 D sphere change and a 0.25 D cyl change. Is that too much? Maybe. Depends…

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@kem @LegendG22

Would you recommend this for someone with high myopia? A family member of mine has glasses that were reduced in this manner (and with astigmatism reduced in one eye only). Do you think there is a benefit to wearing them once in a while as a supplemental normalized to keep astigmatism trending in the decreasing direction instead of increasing?

In my case, with my cylinder being greater than sphere, I was looking for ways to reduce unnecessary cylinder. The astigmatism app helped but did not remove all of it.I felt like my eyes were pulling with full cylinder, so dropped it. I found out that was too much. My replacements included the reduced cylinder strength of my differentials.

Will advise with the next set Later this week.

Astigmatism seems to take a lot of experiment to find a balance between reduction and comfort.

Hey Kem. Would you mind giving a breakdown of your starting, and your cyl, sph reductions as you’ve changed so far and which reductions were good and which were too strong?

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Let me dig up the data…

Edit: For people who didn’t see the data, tl;dr version is, what works for me is either a cylinder only drop, sometimes as much as 1.00-0.75D, or a combined sphere-cylinder drop of 0.25 for each (spherical equivalent of 0.37D). My eyes seem to tolerate that well, but I may also be reversing years of lens induced astigmatism. I never had any until I was well into myopia by several years and diopters.

At the high myopia levels each 0.25 change is less of a percent difference than at low-myopia. (ie: 5.50 to 5.25 is only 5% difference). So I’d expect it to be more forgiving if you were slightly too aggressive.
However, the real goal should be on selecting something that gives lots of “successful” active focus opportunity. If it were me I’d follow the program recommendation of not dropping astigmatism twice in a row. Have at least 1 SPH only change in between drops (which means both differential and normalized get a SPH drop).

The exception to this would be if I tested the drop (via a test-lens kit or other method) and found that it definitely gives lots of “successful” active focus opportunity. Then I would do twice in a row.

Let your vision be the judge. :slight_smile:

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Also keep in mind, at the high myopia level there could be more potential for “over-prescription”. Some of the early drops in both SPH and CYL could simply be removing the “over-prescription” and may not technically count when determining whether you are changing CYL twice in a row.

Definitely test things a lot to get a good starting point reference. Try to eliminate “over-prescription” that might exist, especially as it pertains to astigmatism. Then start the program from there.

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CYL reductions are hell (at least for me). It’s not just that it is a different focal plane, its also that, if I have to go back to the previous power for what ever reason after dropping CYL, I can’t. It seems like the visual cortex has to relearn both up and down revisions*



I noticed that too. The double vision after I reduced CYL lasted for around 2-3 reductions afterward. It was very faint, but definitely a real challenge at first.

I recommend making sure to drop differentials first and then normalized. Try to keep them in line as much as possible to not weird out your visual cortex. I believe you’ll need to do some fuzzy math to keep them comparable (for example, differentials are less Diopters so they will not need as much CYL as normalized in order to be comparable). In my case I was close enough to just eliminate differential CYL and then eliminate it in my normalized.