How to correctly reduce lens for astigmatism?

Here is my biggest question.
I have -2 CYL both eyes.
It is equal to -2 SPH and +2 CYL

if I have -2 Cyl and want to reduce by 0.25 is it correct ?
Should I reduce from -2 SPH and +2 CYL , amount of 0.25 CYL ?
I know for there is difference between these two aproaches

In Moldova all the doctors i went to, gave me straight -2 CYL , end of story.
Read articles on endmyopia but i can’t understand the starting point of astimatic person, as they often ommint the ± sign of SPH and CYL.

Thank you.

The + and - CYL are mathematically equivalent. Here’s a converter you can use. In the USA ophthamologists write +cyl by convention and optometrists use -cyl. They’re both mathematically equivalent descriptions of the same thing.

The axis changes by 90 degrees when you’re switching from +cyl to -cyl.

So as an example -2 SPH +2 CYL Axis 180 is the exact same lens as 0 SPH -2 CYL Axis 90.

There are a few approaches you could try:

Try using 0 SPH -1.75 CYL lenses, with a goal of gradually reducing to 0 SPH -1.5 CYL, 0 SPH -1.25 CYL, 0 SPH -1 CYL etc…

A second approach is to try to exchange some CYL for SPH (this is not mathematically equivalent but functionally equivalent for some people). Many people are able to trade -CYL for -SPH (often when they’re wearing contact lenses). You could try glasses with -0.5 SPH and -1 CYL and try to work down from there. (The rule of thumb for exchanging cyl for sph is that one diopter of cylinder can be traded for half a diopter of sphere. It doesn’t always work.)

It’s not really part of EM but some people (myself included) have had good luck with eye exercises for astigmatism. There are various free apps you can download, but most of it involves looking at images that make astigmatism noticeable, and then trying to clear the image.

Move far enough away from the screen that the spiral appears glitchy, then move closer a little bit, and try to follow the whole circle with your eyes, keeping the image clear. Then see if you can move a little farther away and do the same thing. You can tilt your head from side to side (changing the part of the image that should be glitching out according to the axis of your astigmatism).

If I were you I would use either no glasses for close-up work, or glasses with a greatly reduced prescription for close-up work (maybe -0.5 CYL in each eye, only for close up.)

Unfortunately there’s some trial and error involved in figuring out what works for you.


Yes, the idea would be to reduce 0.25D from the cyl and let your brain sort out the new images when processing them. However, some people find it easier to do if some of the cyl dropped is added back in SPH.
CYL means different correction within the same eye, “SPH only” means the same correction all over the eye. Having “CYL only” means that when you are not wearing corrections, a perfect circle looks oval to you or a circle with oval double vision…
Usually there is a habit that contributes to high cyl. E.g. you move your eyes up and down a lot more often than from right to left, or the other way around. You have strong, contrasting lights from above (rooftop or basement window) or from a certain direction, you hold your head or rotate your body in a certain position (watching TV twisted on the sofa), etc
The axis will let you know which is the direction not used regularly in your every day life.


“The axis will let you know which is the direction not used regularly in your every day life.”

So if I see blur on vertical lines but see horizontal lines better what would that say about my habits? I have -1.75 Cyl in both eyes and I am a programmer using 2 computer screens 8h/day


I use computer for 2 decades and have the opposite astigmatism. Just try to fix it. Who knows why it happened.

Assuming the 2 computer screens are next to each other, you are moving your eyes left and right during the working hours a lot. (vs. students who have an elevated laptop in front of them and a notebook between them and the laptop who move their eyes up and down more.)
It’s important to note that it may be that the horizontal eye movement is a lot more but it can also be that the vertical movement is a lot less (never walking outdoors raising the eyes to the level of straight ahead or over). The astigmatism result will be the same.

When looking up, most probably you move your head with the eyes, while when looking on the monitors your head almost stays still and your eyes are moving along a longer line before you move your head with them. And anyway, most screen workers simply have no natural opportunities to raise their eyes higher than straight ahead, and the typical cylinder axis is around 90 degrees (+/-15).

A bit more on it in this thread: