Does sph reduction always available?

The optometrist found my current prescription is -3.75, - 3 with 1 astigmatism but found it’s best not to give a full 1 cyl correction so he gave me - 4, - 3.25 with 0.5 cyl correction. 0.25 diopters to replace 0.5 astigmatism.

Now, if I want to make a spherical reduction, how can I do it exactly? Because the 0.25 I reduced thinking it is a spherical reduction actually exposed the astigmatism it was ment to disguise and now I find myself dealing with 0.5 astigmatism and not spherical…

If you are talking about contacts this makes sense. The correction of .50 is too small. If you are talking about glasses the .50 can be added to lenses. Zenni will do .25 cyl you just need to ask for a prescription for glasses that has the correct axis. If that’s not an option there some tools in let meow to help determine axis. I wore contacts for over 20 years that did not address cyl. And the astigmatism didnt go away so I have reduced by .25 cyl as a way to equalize. And I do see the astigmatism effects now that I have removed it. But there is improvement by treating it like a regular .25 reduction.

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So in your opinion there is no way to do a sph reduction…
It might be the only practical solution, but if I think about it, there is a bit of a problem. Let’s say I reduce, as you said, 0.25 cyl only and hopefully my eyes adapt and correct them selves accordingly. After that, the safe reduction to do is to follow that with spherical reduction, let’s say 0.25 sph reduction. But that reduction still contains inside the remaining uncorrected 0.25 astigmatism. Meaning, two cyl reductions in a row.

So it still means, reducing first only 0.25 cyl isn’t necessarily the right way.

What your thoughts about it?

I’m a little confused about the question. You can remove the cyl and add sphere instead as a method to remove astigmatism. But if you find that it is noticable and hasn’t been corrected before then you may want to do a reduction process. What I recommend is to read more in the forum on astigmatism and see what will work for based on your reading. Many of us try something and find it doesnt work out like we thought.
If you get differentials without cyl correction and those dont work at least you can use them later when you reduce. The cyl axis can make a difference in the correction so that’s why I recommend a prescription. But others do this without optometrist too. Just learn a lot about it before you decide.

This is kind of confusing. Does this mean: “The optometrist measured my needed prescription at OD: -3.75 -1.00 x axis, OS: -3.00 -1.00 x axis. but actually wrote OD: -4.00 -0.50 x axis, -3.25 -0.50 x axis”?

I’m guessing you wore that for a while and are now considering next steps?

I would consider this set of glasses a cylinder reduction as it’s a cylinder-for-sphere trade. Assuming you’re seeing well with it and ready for your next reduction, I’d say reduce the sphere only by +0.25 in both eyes for a spherical reduction and leave the cylinder the same.

Wear that until you feel comfortable/can see well, then do another round of cylinder reduction. You could either do a +0.25 or +0.50 cylinder reduction, since as you point out, it’s usually a 0.50-cylinder-0.25-sphere trade. Or you could do another sphere for cylinder trade, but I think that’s just keeping your spherical equivalent the same for longer. Realistically by then you should be close to 0 cylinder, and not have to worry about it. Either way, you’re working on a spherical equivalent reduction.

I’m currently going through something similar. I was wearing -1.50 -1.50 OU in normalized, and -0.25 -0.75 OU in differentials. Something told me that my cylinder was keeping my acuity from improving, so I traded cylinder for sphere: -1.75 -1.00 OU in norms, and -0.75 OU or -0.50 OU in diffs (depending on whether I need more or less for my immediate setup). My next round will likely be a set of -1.50 -1.00 OU norms, with no change to my diffs (I’ll just switch to the -0.50 OU and nothing, full time).

I’m planning to wait until after that round to decide whether to drop a quarter or half diopter of cylinder. Hopefully Covid-19 doesn’t kill Zenni.

Or me.

I hope this helps. Please let me know if I misunderstood the question.


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Yea you didn’t understand what I ment to ask

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I’m not entirely clear on this either. :thinking:

Generally, cylinder reductions best to start with differentials (where you need less of it, plus you have a very consistent environment with few changing variables). The tiniest bit of directional blur that doesn’t cause any eye strain (you just want your brain to have a little bit to work with to re-align).

All depends though where your eyes are and important to follow where you can tell they “want” to go rather than trying to force a cylinder reduction.

If spherical reductions are readily adapted to, it can make sense to just take advantage of that and then periodically check in and see if a bit less cylinder produces any ghosting / directional blur.

There is almost always a reduction that feels “right” as opposed to sometimes what we think we want to do next.


Yea you got me right. The problem is I get weak vision because the 0.25 reduction is actually a 0.5 astigmatism reduction…

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It is awful at first but gets better…staring at things in the middle distance helps. The “Astigmatism” app on Google Play also really helps.

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How does the exchange of cyl to sph you made going for you?

It’s only been a week and a half. It seems to be OK. I’m planning to be in it for a while, then will try a spherical drop.

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I will try to clarify my question: in some cases the 0.25 diopters we reduce weren’t there for fixing spherical issue but astigmatism issue. In this situation I think there is no way to start with spherical reduction but only cyl reduction.
Like in my case, the optometrist found - 3.75,-3 with 1 cyl but then he decided to reduce 0.5 cyl correction and add 0.25 sph instead.
After that, for the normalized, when I reduced these 0.25 sph thinking I made a spherical reduction it seems I was actually making 0.5 cyl reduction. :confused:
Or it is still considered a spherical reduction?

That trade was a net zero spherical equivalent exchange.


Yes, minus 0.25 sph for the reduction of 0.5 cyl he did, and he made that trade because giving me the full maximum cyl correction can cause vision looks weird a bit.

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It seems these 0.25 diopters I reduced are indeed a reduction of cyl, for the trade, and after a month it seems more difficult to bare. It seems also that there is no way to make a spherical reduction here. . It is awkward in some way because my previous prescription was without cyl correction and my current diff are without cyl correction and after wearing the norms with cyl correction the diff are also doesn’t fit anymore. Wow, what a mess… :frowning_face:

From one hand my prescription still needed a cyl correction but after bringing cyl back my vision isn’t good as without the cyl correction

I think I won’t have a choice but to bring back the 0.25 diopters even if it means a wearing a full correction and let the astigmatism subsides with the diff…

The question is how can I make wearing the diff again without headache. When it’s a new normalized it’s just going without glasses for a while but diff? Maybe trying to read without glasses? I am not sure about it…