Difference in CYL - Differential and Normalized

Hi all! I was wondering, if it is bad to have difference in CYL values in my Differential and Normalized. Currently, I have -0.5 CYL correction for both eyes. These glasses were my miscalculated first differentials as my earlier prescription was over corrected. Now, I want to use them as normalized as I can see 20/30 in LE and 20/30 with Double vision in Right Eye on Snellen.

Now, I plan to buy differential for reading purpose to practice close-up AF with a book. Today, I checked with Optometrist and he gives -1.00 CYL in right eye which was correcting the DV and LE was fine with 0.00 CYL.


Yes this is very bad. You want the L / R ratio and astigmatism correction to be a same on all your glasses. I recommend you do some reading and video watching on the EM site where this is al covered.

Kind regards,


Hi Maurice, thanks for replying. Actually I am with EM from more than a month and read the info too, but here’s the specific question:

Almost a month before I got first reduced prescription (-8.25 and -8.00 just -1.5 Diopter less in SPH keeping the CYL -0.5 same). But since I have high Myopia -8/-9 or may be I had earlier overcorrection, those reduced prescription were giving 20/30 in LE and 20/40 in RE already. In my RE, I am having DV with these glasses, but vision with both eyes just shows a little blur.

Now I used them for nearly one month and got eyes checked by Optometrist today.
He confirmed my prescription same as my reduced ones, but with the change of CYL
OD: -8.5 SPH -1.00 CYL instead of -0.5 earlier
OS: -8.00 SPH 0.00 CYL instead of -0.5

That’s why I was asking if the CYL values are changed during the course of EM, should you not change? Now, since we are advised to keep a time window (4-6 weeks)between changing Normalized and Differential, so that you keep one pair still the old one whereas other need to be changed how should we proceed?

Sorry, I am new member and having problem recognising what could be Diopter specific advice. Without mentioning Diopters the question looks vague.

Best regards

I would give priority at the L / R ratio and astigmatism correction to be the same in al your glasses, otherwise it is very confusing for your brain. Further (re)read the stuff about astigmatism and prescription complexity reduction. Reducing it or getting rid of it if you can would be beneficial. For the right eye it is already gone you say. Putting in more cyl for the right eye would be a step in the wrong direction IMHO.

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Definitely not a good idea to have a higher cyl in your differentials (near vision glasses).

As for having a lower cyl in your differentials, that is a very good question, and I hope you get some feedback on it from people who have tried it.

I would encourage you to drop the astigmatism. In my experience astigmatism isn’t really natural for the eyes, neither are glasses. I’ve dropped my astigmatism and it went away.

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Dropping it may indeed make sense in this situation because of the increased asymmetry in the new rx. Problem is, you don’t know how it’ll work out until you try.

@Aparna, were the new glasses ordered/made yet? Assuming you’re getting them through your optometrist (and paying a lot), why not ask him/her if they would be willing to write an order for glasses without the cyl correction, since one eye apparently decreased in cyl and the other increased, and you want to keep things symmetrical if at all possible. They will probably increase the power by 0.5 (to maintain spherical equivalent) in the right eye if this is done.

If you don’t want to deal with all of this, do you have a place you can purchase your own glasses from?

Hi all! Thanks for helping me out. Since joining EM I have been analysing the old prescriptions, although I didn’t have all of them but still have the ones from last 10 yrs and in them CYL values are ranging from -0.5 to -1.75 in both eyes.

  1. What I feel is my Astigmatism was lens induced or better say Opthalmologist - optometrist induced. The lowest CYL value of -0.5 was given before3-4 years when one Opthalmologist converted CYL value to higher SPH (from -7.75 in both to -9/-9.25)leaving CYL only -0.5 in both eyes. I was constantly on the move so all the OPs are different.
    I never paid attention and just followed the prescription.

  2. From EM I learnt measuring the Blur distance etc. and found that my LE is only -7.75 on EM calculator while right is -8.75 (I have that scale with text type tool) even in the first week, so I guess they have been always overprescribing the left. That was the reason, the first differential I ordered became now full prescription just the RE is lagging behind. Of course 1 month of good habits and outdoor time would have played a role too.

I feel that the Diopter difference between L/R is what I measure consistently on CM calculator i.e. 0.75 and not 0.25, which I was wearing from last 3-4 yrs. I agree that, CYL in RE should not be increased, so I plan to make it 0.75 SPH difference in both eyes with only -0.5 CYL in RE and dropping the CYL of LE.

Yes, I too thought about that, but the problem is DV in right eye which I saw only when SPH were reduced to -8.25. I am not sure if RE will accomodate, may be dropping in two reductions, -0.5 now and -0.5 in second reduction would give RE bit time.

This is what I was wondering as my normalised glasses will have LE CYL -0.5 and RE -0.5 but differentials would have no CYL in LE. would it cause problem. I plan to first buy new differentials then may be after 4-6 weeks new normalised.

I have learnt so much with EM and realised that how naive I was to believe whatever was said to me regarding eyes. I sincerely thank EM, Jake and all of you for increasing awareness and helping out people.

Thank you

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No, I haven’t ordered the new glasses. Here in India we have an eyeglass company that offers Home eye-check up. I never believed in that as was cautious because of high Myopia and went always to Dr. Since I had my check up with Dr. just a month before and I wanted to only buy differentials, I ordered home eye-lens test so that I can try the close-up prescription at home. Glasses I can order online by putting prescription and avoid the hassle of asking them to write

Still I am not sure if RE will accomodate without CYl at once. Would it not be safe to increase SPH by 0.25 in RE and keep the CYL to -0.5?

@Aparna, if it were me, I’d just go by the old cyl correction and new sphere correction when ordering, because I’m used to that amount of cyl already. That way, you’re only changing one thing at a time (sphere). Then 4 months or so down the road when I needed another new pair of glasses, I’d work on reducing the cyl. But that’s just me…you might decide to take a different approach. But since you have the new rx from the exam, you know your sphere needs a reduction, so really there’s not much of a choice.

But yeah, I’d have the exact same concern that you brought up about changing too many things at once (and would be afraid to change the cyl right now because of that).

When you do eventually reduce the cyl, it’s probably wise to keep the spherical equivalent as you said. (The formula is: 0.5 cyl = 0.25 sphere in terms of power.) Make sure you keep the sign (plus or minus) as well. In other words, you add half the cyl to the sphere to get the spherical equivalent. But that will probably come later on for you, rather than right now since you’re working on sphere right now.

I wouldn’t increase the right eye sphere unless I really needed to. If you can avoid increasing the diopter difference, don’t. Since your new rx is very recent, you can probably avoid having to do that.

Again, I would keep the diopter difference and the cyl the same as with what you’re currently wearing, and only change the sphere. That is what Jake recommends.

I also forgot…how long have you been using differentials already?

Good luck, and let us know what you end up doing for normalized.

Until Jan 2019, I was wearing OD: -9.25 -0.5 10, OS: -9.00 -0.5 170. After Jake’s E-mail course, Cliffgnu’s E-book and my Retina specialist’s advice I got this new prescription on 1st Feb 2019 OD: -8.25 -0.5 10 OS: -8.00 -0.5 170. I call this reduced prescription instead of “differentials” as it can’t be used for close up AF. With both eyes I nearly see 20/25 in daylight. With right eye alone 20/40 or AF 20/30 with DV.

Because of that, my feeling is I may not be able to do AF if I don’t increase Diopter difference as the Blur horizon of two eyes will differ too much. close-up AF I haven’t experienced so far as the glasses are too strong.

I feel like following this advice for these differentials, will update how it goes. They are close-ups so, if they don’t work eyes will let me know soon.

Thank you very much!

Unfortunately you won’t know which way is better until you try one option.

Just make sure you keep the same diopter difference if you’re using multiple pairs of glasses. And the cyl as well.

@FMR Just to complement you on the nice new kittey picture! :blush::smiley_cat:


Yes, Thank you! I will take another week and then decide on differentials. I really feel so lucky to be in this community. May be I will drop CYL altogether. In my case difference in blur distance is only 0.5 cm (-8.25 to -8.75). Somewhere, I need to get started.

Hi Bobby, qn: how much was your CYL values? and did you just dropped it or converted into SPH values. Also, for normalized or just for differential or for Both?

Hi Aparna,

If you are able to find a differential prescription without cyl that is comfortable to use I think it would be the best option. Only the difference with the norms is a bit problematic then. Normally when you use your diffs and norms in the right situations both will give defocus stimulus in the same direction most of the time. But if you have one pair with cyl and one without than the eye will have to move in the direction of less cyl in one pair and in the direction of more cyl in the other to get things clear, possibly ending up with your eye in a funky state.

I dropped my astigmatism completely when first starting out; I had 1.50 and 2.50. I also dropped sph slightly

Wow. That’s a very big drop! How did that work out? I have the same cyl correction as you had. I dropped to -1 and -1,5 and even after some months it is still noticeably difficult at times. Especially the RE where I dropped the whole diopter at once.

As for the OP: I tried normalized and differential glasses with different cyl values and wasn’t happy about it. I changed my normalized to match the close up cyl values and only work with different sph values now. Much better, wouldn’t want to make the same mistake again.

It wasn’t too bad. With active focus I was able to read words. Eventually each eye is able to see in the same direction.

Hi Maurice,
What is your opinion about changing Norm. and Diff at once now and stop using the current glasses. I would then order two pairs with No cyl and only difference in SPH by keeping L/R Diopter difference same. My current prescription for LE is anyway full Rx, so soon I will have to look for new Norms.