New differential and where to active focus

so I just got my new differential. Before that I had been wearing and active focus with my normalized for a month over.
My normalized prescription: R: -4.25 -1.25 10 L: -4 -0.5 180. I didn’t reduce the cyl on my normalized because it was my first normalized.

so my new differential is R: -2.75 -0.75x10 L: -2.5 (no cyl).

So on my differential, I get SPH blur at 66cm and directional blur at 50cm. at what distance should i do active focus? Is it at SPH blur or at directional blur?

Not diopter-specific advice, but why don’t you try increasing cylinder a bit to move you directional blur back a little? I have it at 50cm as well and I can tell it is extremely annoying, not what you would want for comfortable work. If you have a friendly optometrist, they could try to measure differentials for you so that you don’t have blur before 60-70cm.

And to answer your question, it does not matter at what distance you do active focus. What matters is how sustainable it is. You can very much sit at the edge of myopic blur and AF for both but that’s going to cause you strain and the very point of differentials is to just sit and work comfortably without strain. Distance AF with your normalized is going to make more difference anyway. This is not plus lens therapy where you get your eyes constantly working to resolve blur while you’re on screens, this is just to address the excess strain.

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thank you for your explanation. To push the directional blur gets back A little do i have to increase sph correction ?

like diff: R: -3.25 -0.75 x10 L: -3.0(no cyl)??

or I just increase the cyl correction like diff: R: -2.75 -1.25x10 L: -2.5 -0.5 (no cyl)??

I’m just asking what you think you would do if you were in my position

I would probably go to a professional for help. They could try on lenses with their trial kit, and you could notice the difference in real time. As a DIYer here I self-experimented a lot and I still don’t know exactly how lenses behave for any given pair of eyeballs.

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I’ve been thinking about astigmatism quite a bit recently. Just trying to build pictures in my head of why it manifests as directional blur, etc. I’ve been meaning to update the page on the wiki at some point, but haven’t got round to it yet.

With reference to the picture on and assuming your astigmatism is “regular”

For close enough objects, I’m guessing that the eye uses accommodation to keep the middle of the spread-out focus on the retina, so that some image is focusued in front of the retina, some behind, giving a circular blur.

As the object moves away, accommodation is no longer able to sustain that, and so the whole mess moves forwards, and this is how the directional blur manifests - the axis which focused in front of the lens moves further forward, and so spreads out even more by the time it reaches the retina. The other direction, which was spread out on the retina because it was focused behind it, now focuses closer to the retina and is sharper. I’ll do some sums with your numbers to see if that’s consistent.

So if I’m right, the answer is that you can do either to improve the directional blur… increasing spherical will push back the “circle of least confusion”, allowing you to keep it centred on the retina. Or increasing cylinder will reduce how spread out the focus is, and therefore also improve things.