Astigmatism & Lens Complexity
Welcome back, [s2Get user_field=”first_name” /]. If you wear a ring, for years, on the same finger, you can take it off, but it’s presence will still show on your finger.
There will still be the lighter skin, where sun never reached. There may be a bit of different texture of the skin even. The physical constraints created by the ring leave a mark, that even when the ring is removed, will take time to disappear.
Our bodies adapt to the influences of our environment. Clothing, exercise, diet, all significantly affect our physiology.
The same of course is true for glasses. As you well know by now, the focal plane change created by the lenses does more than just correct a vision deficiency. Unless this correction is applied very carefully, and only used at the necessary distances, the glasses will contribute to further affecting your eyesight – primarily by contributing stimulus further adding the axial elongation of your eyeball.
We must be careful in how we handle these prescriptions. There are no less dangerous than any prescription drug, and should always be considered with hesitation and a clear understanding of the exact prescription values.
The casual nature of focal plane prescriptions got us to where we are today, with you reading this, working to reverse its effects.
Astigmatism correction, likewise treated often casually, aids to further distort the shape of your eyeball.
Generally speaking, astigmatism corrects for myopia on a specific axis. This is assuming that your eyeball is not perfectly round, focusing light at different points, in different areas of your eye. This tends to happen as axial myopia progresses – your eyeball stretches, and as a result creates irregularities in its shape.
Depending on your myopia degree, and astigmatism correction, you may need some of this prescription.
As we talked about in #68, if you are a low myope, the astigmatism correction is likely unnecessary. We will soon discuss to what extent, and how to best wean off that part of your prescription.
If you have high myopia, and a significant astigmatism correction, we want to apply the same logic as we do with the normalized prescription:
We want to very slightly underprescribe your astigmatism correction, to encourage active focus.
This is similar to the practice you already so well know, with pushing and pulling focus. We don’t want to deepen the focal plane error by providing a significant astigmatism correction. If we do, this further encourages physiological changes that negatively affect your vision.
On the other hand, we don’t want to casually eliminate the correction altogether, as this just creates eye strain and no positive stimulus.
In some cases, I like to counter some astigmatism correction with a bit of cylinder increase, trading some astigmatism correction. While this varies on a case-by-case basis, upcoming installments will provide you with some tips on how to assess your own case, and consider this correction swap.
Again, we never want to change a prescription, without knowing specifically exactly why and to what degree. Improper prescriptions create eye strain, adding to myopia symptoms.
The ultimate goal is to continually reduce the overall complexity of our prescription.
The general rule applies, that we always have to work close to the edge of focus. Heavy underprescription, or eliminating a prescription aspect that the optical reality of your eyeball surface requires, serves no benefit. Many times, we just have nowhere near the correct corrective lens shape to follow the reality of your eyes.
We have already corrected this, for cylinder – you know how to measure, and you have the correct myopia correction prescriptions.
Now we are getting into the same principle, but for the slightly more complex subject of astigmatism correction.
Without having explained it in the core part of the program previously, we already laid the foundation for this upcoming astigmatism correction strategy:
We eliminated astigmatism correction for up-close work.
I left out the explanation at the time, since there was no reason to add complexity to the initial workload at the time. You likely had enough on your mind, just trying to sort out all the new information at the time.
But you didn’t need astigmatism correction for differential prescription, which is why we left it out.
Your eyes now already are habituated to no axis specific correction, at the near distance. You may also be already acclimated to no axis-specific correction at middle distance, if your myopia degree was low enough to warrant application of our previous discussion of middle distance and the 4th Focal Plane.
So this is not really an entirely new topic for your eyes, I just did not explain the astigmatism application, as we were already working our way into this arena.
I’m looking forward to working with you on this task, of reducing the net complexity of your prescription. We will look at the various ways of measuring and eliminating some of the astigmatism correction, giving you a lens with less optical distortion, and a clearer path for light to reach your retina.
Next up, we will begin discussing some of the cases you may be able to completely eliminate astigmatism correction in your next normalized prescription change.