Astigmatism reduction questions

I am not quite ready to actually do an astigmatism reduction yet, but have been looking up the info. I have quite a bit of astigmatism: -2.25 for left and -1.75 for right.

So, I am supposed to do close-up reduction first. I see people talk about doing substitution and stuff. For the close-up reduction, am I supposed to just reduce or substitute (0.5cyl for 0.25 sph)?
How much am I supposed to reduce? Just 0.25 or go until I see blur?

When do I move to the next reduction? Do I move to the next reduction when I don’t see blur anymore?

Most people would reduce the cylinder to just what they need in their differentials from the start. No diopter-specific advice here, but if you just reduce the cylinder that you don’t need for your differentials, I personally don’t call it a reduction. It’s just part of getting fitted for differentials. Just don’t reduce further all at once.
Astigmatism behaves differently for different people, and tolerance for reduction varies. So my humble opinion would be to say that, whatever you choose (a first big reduction or -.25 at a time), at least don’t go all the way from full cylinder correction to a reduced cylinder correction that gives you a blur challenge.

Sphere for cylinder trade-off is a gamble that seems to work for some people, but that is a bit of a pro topic. If your myopia is low enough that you can’t afford to make two spherical reductions between every two astigmatism reductions, then maybe you could consider it at some point. But this is very, very personal. And very, very unpredictable. So if you have a test lens kit, better ask it about what works for you or doesn’t.

1 Like

Okay thanks.
How do I know when it’s time to move on?

I’m not sure I understand. Are you asking when you know it’s time to reduce cylinder?
Maybe this article will be of use:

Sorry. That wasn’t what I meant.
Let’s say I dropped my cylinder for closeup, when should I go do the normalized? Just the normal 4-6wks?

Your differentials are a bit like a testing ground, so you would reduce cyl in your diffs before reducing cyl in your norms. But keep the balance betweent he eyes the same in diffs and in norms.

For example:
If you have Right Eye -4.0 sph -1.5 cyl and Left Eye -3.50 sph -2.00 cyl
then you could (if you wanted) decide to get differentials that were 1.0 sph lower and 1.0 cyl lower.
Since 1 diopter of cyl is similar to 0.5 diopters of sph, that would give you approximately a 1.5 reduction, with would be a reasonable choice for differential.
That would leave you with diffs that were Right Eye -3.0 sph -0.5 cyl and Left Eye 2.50 sph and -1.0 cyl.
But in your norms, you would still have all your cyl.

Then after having these differentials for 4 to 6 weeks (assuming they feel good, and give you just the right slight amount of blur), you would then change your normalised. You could wait longer than 4 to 6 weeks if you wanted as well.

The only time I know of when you would be not waiting the 4- 6 weeks minimum between changing diff and norms, would be if you were changing something about the complexity, like if you were equalising some sph or some cyl. Then you would change both diffs and norms at the same time.

So you wouldn’t want diffs that were
Right Eye -3.0 sph -0.5 cyl and Left Eye 2.50 sph and -1.0 cyl (unequal cyl)
while wearing norms that were
Right Eye -4.0 sph -1.5 cyl and Left Eye 3.50 sph and -1.5 cyl. (equal cyl).

I hope somewhere in my big ramble your question got answered. :crossed_fingers:t2:

1 Like

@gemilymez that’s awesome. Thanks.

Oh, I didn’t clarify, but you may already know, but for norms, you don’t follow you differential cyl drop by dropping the same amount of cyl in your norms. Just small steps every time, like 0.25, or maybe 0.5cyl if you are adding back in 0.25 sph. You can drop a little more cyl in your diffs for the same reason you drop more sph for diffs - close up. Besides that, one step at a time.


Thanks for the clarification. I assumed that’s what you meant from doing something like that with spherical.

1 Like