Review of Astigmatism

Although it dates from 2006, I have found this review on astigmatism clear and useful.

https://onlinelibrary.wiley.com/doi/full/10.1111/j.1444-0938.2007.00112.x

I remember a while back reading somewhere that the visual cortex has an easier time accommodating mirror image astigmatism than parallel astigmatism. I have not been able to find this again. If anyone else has picked up on this, please let me know. I have oblique mirror image astigmatism and find that my visual cortex doesn’t have too much trouble balancing this out in uncorrected vision. I had hoped to find something in this review, but no luck.

Edit: Alas, I seem to have found something that seems to falsify my hypothesis rather than confirm it. But as this is in induced astigmatism it may not count as much. I have had many years of neural adaptation to my uncorrected astigmatism. This is from another review of astigmatism.
https://onlinelibrary.wiley.com/doi/10.1111/opo.12128

Measures of stereoacuity are also reduced by monocular and binocular induced astigmatism, with the most pronounced effects found for induced binocular orthogonal oblique astigmatism (i.e. axis 45° in one eye and axis 135° in the fellow eye).106

I found it interesting that both studies pointed out that certain sustained eye movements can lead to astigmatism, I didn’t take the time to fully read them but it seems like it’s been observed that reading even as little as 60 minutes creates a measurable degree of ATR astigmatism.
I suppose it makes sense that repeating the same habit over time causes permanent changes to reduce stress, similar to myopia.

My case is also oblique mirror image but fairly close to vertical in both eyes, I find that they don’t cancel each other out and depending on the lighting and what I’m looking at (e.g. neon lights at night) I can actually see both ghost images in binocular vision, perhaps over a long period of time you’ve adapted to it well but it seems like I haven’t yet, I also believe that due to a change in my habits I had a shift in axes early last year which was around when I felt like my vision worsened after a period of intense close up that involved a lot of up-down movement, with my head mostly tilted down while I was looking up.

I’m still trying to wrap my head around how this works but based on what I figured out so far if the astigmatism has obliquity then some degree of cyclotorsion that happens quite regularly and in specific directions seems to be a cause, so the axis shifts in the opposite direction of the stress that’s induced often to counter it, I’ve been trying eye movement in the direction of the ghost images and in as little as 2-3 minutes I see a small temporary change, as the change is quite small it’s mostly noticeable on high contrast details like lights at night in the distance.

Yes, 30 years of uncorrected vision except for the very little driving I do. In that period I had a big shift in axis in the left eye (close to 80 degrees) but no change in the axis of the right eye. This also doesn’t map neatly on the age-related shift in axis (I am 75)

I have no records at all of my prescriptions over the past 60 years or more of myopia. So I have no idea of the rates of progression. When I first found EM I had no idea of what diopters meant, other than that higher was worse, and not a clue about astigmatism. This has now been corrected by a good deal of reading, both from the EM resources and online.

In the guide we are working on, I don’t want to include any exercises for astigmatism, as I want to keep it EM-centric (no exercises needed). But there is nothing to stop people from trying exercises as well, and no harm in sharing them on the forum.

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Just wondering. Is mirror astigmatism when the axis is 90? Is that the same as vertical = axis 90?
My axis of astigmatism in both eyes is 180 so that would be horizontal right?
to me that makes sense but i find all the additional descriptive terms of astigmatism confusing at times.

Yes they are, and it is usually necessary to refer to a diagram to fully understand

Mirror image is when the axes are not the same, but they would be the same if you matched each one with the mirror image of the other. An example would be an axis of 130 in one eye and 50 in the other. It could also be 110 in one eye and 70 in the other. If you draw these lines on a fan diagram you will see how the one is the mirror image of the other. They are not likely to be identical images, as there is often a slight difference. For example my axes are 50 and 120, not quite a perfect mirror image. Axes that are the same cannot be mirror images. For example, an axis of 110 in each eye does not create a mirror image.The lines run parallel to each other.

If this is still confusing, I will draw a little diagram and post it.

that makes much more sense now. Thank you! My axis are the same in both eye and are both 180. What would that be called? How would that make a difference compared to astigmatism that is mirror image?

This is not really known, and I suspect it makes little difference.

If we view the eye as a sphere, “against-the-rule ” is astigmatism where the steepest curve lies near the 180-degree meridian (imaginary line connecting east and west points of the cornea), and “with-the-ruleastigmatism (line connecting north and south points) is near the 90-degree meridian.

okay, ive seen the against and with the rule terms. Im beginning to understand. :slight_smile: Thank you Ursa

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