Thoughts on first diffs before purchase

You guys are amazing and I am thankful for stumbling upon you lot.

After some great and needed advice I realise that I need both diffs and norms for this to have a chance. I have not worn glasses really most of my adult life but through constant strain ( possibly) sitting at a desk for bets part of 8-10 years and working on mobile and computer, my eyes needed help. So with low sph and higher Cly I am going to try and leave the sph in diffs and reduce the cly by the following:

Last prescription :

R : sph -0.25 Cly -2.75 axis 80
L.: Sph -0.50 Cly -2.25 axis 86

First diffs possibilities :

R : sph -0.25. Cly -1.75 axis 80
L : sph -0.50 Cly -1.25 axis 86

Or just -2.25 and -1.75.

The glasses are not expensive but getting some diffs must help astigmatism close up work ? Thoughts ?

Last prescription :
R : sph -0.25 Cly -2.75 axis 80
L.: Sph -0.50 Cly -2.25 axis 86

If these were my eyes (they are not) I’d go for:

First norms as @nycmao suggested
R : sph -0.50 Cly -2.25 axis 80
L.: Sph -0.50 Cly -2.25 axis 86
This is a 0.5 cyl drop in the right eye replacing it with an additional 0.25 in the sph

First diffs:
if feeling adventurous:
R : sph 0.00 Cly -1.75 axis 80
L : sph 0.00 Cly -1.75 axis 86
or if being conservative
R : sph 0.00 Cly -2.25 axis 80
L : sph 0.00 Cly -2.25 axis 86

If you go for equal cyl in distance correction, keep the cyl equal in the diffs, too. Otherwise your brain will be totally confused.
Whether you keep the same cyl in diffs and norms, or you have a bit more (equal) in norms and bit less (equal) in diffs, that’s your choice.
You’ll only know which one is the good one by trying them out.


Makes sense to make sure I keep changes the same in diffs and norms. Adventurous not so much :wink: but for the price conservative looks okay. Keeping both eyes the same may be the smart move…but changing the sph is something I ain’t sure on… so it’s representative of good vision and you think adding 0.25 to my weaker may aid it and equalise nicely… dropping it means I ain’t got any clear vision as such just the astigmatism…

Dropping -0.5D cyl and adding -0.25D sph is an opto practice, not an EM method.
This is what my non-EM friendly opto always did so I could wear simple contact lenses and not toric rotating ones.

Since your uncorrected eyes are zero, it would make sense to keep all other focal planes equal.


Yeah so keep the sph and Cly the same and substitute the 0.5 d in Cly for +.025 in sph… Equalising them…that does not sound to bad…not a massive change overall I guess…

1 Like

One last point if my lenses are over corrected generally speaking then leaving my good left eye over corrected ,not a bad idea ?.as this would mean it’s going to get used it this more…I think the optician hinted it was about correct for my left(possibly over over corrected) shrug… I will only know if I get them I guess…just letting my good eye go with the over corrected lena

If you wear them for real distance vision time, you can not ruin your eyesight.
Don’t wear them with laptop or tablet or smart phone distances.
With TV, try and see if you can wear just your diffs (should be enough).


Yeah I will only use the diffs for close up. Currently not wearing anything for close up and for driving I’m using the new prescription ones…(for now). I mean adding or changing the sph in my weaker eye should be okay as I’m compensating it by the 0.5 reduction. Yeah think my first diffs will be :

If I got it correctly :smiley:

Wait on this reduction is rather conservative as I won’t be able to reduce much for the norms…hhmm maybe go to less for diffs…and to the above for norms.

1 Like



On it , thanks :+1:

1 Like

Ordered my norms as above but diffs I was thinking -1.75 on both but would I just leave the sph the same -0.5? On both so only changing the cly

No. Diffs are used for close up, so reduce the sph to zero or you will be overcorrected when looking at things close up
R : sph 0.00 Cly -1.75 axis 80
L : sph 0.00 Cly -1.75 axis 86


In my experience, astigmatism only comes out with some effort. It’s not hard, but don’t overdo it. Finding a balance of not too much and not too little cylinder is key to managing improvement of astigmatism.

You’re right to try to get the astigmatism out of the way first. It’s tougher with a low sphere starting point, but can be done.

Good luck!



Thanks Kem. I am doing 0.5 reduction in my right and adding the 0.25 sph … And kept the left the same for now. That’s for my Norms at least… and for diffs,I think I am going to go down to 0 sph and to -1.75 in both

1 Like

It’s tough when you’re trying to get rid of cyl, equalize, and reduce. It’s probably best to work on one plane at a time.

See the Reducing Complexity post on Jake’s website.

Ah ok so you saying I shouldn’t touch sph when adjusting the cly. I thought that was the case but I have done his with swapping 0.5 Cly to 0.25 sph for weaker eye.

There are three options. Trade cylinder for sphere, make a minor drop in cylinder only, and leave cylinder alone and decrease sphere by itself.

Since your astigmatism is the greatest component, you probably want either of the first two.

Whatever you do, you’ll probably want on both sides as a general rule. That is, until you’re actively seeking equalization.

The trade can get you more sphere, but realize your spherical equivalent is the same as what you’re going from in the new correction. It absolutely will change your eyesight. Just be certain you’re going where you want. There’s plenty of time to plan (and plenty to second guess afterwards).

Especially at the beginning, big bites may not be the best course.

Just a few thoughts. I’ve been doing this since 2019, and I’ve gotten improvement, but there were many missteps


Yeah it is hard to know the best approach really. Well I have equalised my Cly in my norms so that my r is 0.5 less but added the .25 sph. So my eyes are equalised for distance. So I won’t play about to much with the sph on my diffs… question is to leave the sph the same as norms and just drop my diopter in Cly… some kind members have suggested dropping the sph correction and lower the cly at the same time(diffs).

Not ordered my diffs yet but could be; sph -05 in and -1.75 in both. So from norms to diffs I am equalised.

It’s about not straining my eyes and making the situation more complicated in any fashion… You been doing it some time and made some good progress I imagine.

I have ready given you everything I can short of actually telling you exactly what to get on Facebook yesterday… that said I think your normz plan with work fine and this diffs plan

Sounds like a decent start point. You are probably over thinking this a bit, in the end you can’t for sure know how the correction will suit until you put it on. The sooner you get them the sooner you will know if you need to adjust and by how much. The only alternative to the make your best guess approach is a supportive optometrist. If you can find one, great! But they are rare.