Not Lens-Induced (Idiopathic) Corneal Astigmatism: Possible Causes

Some people have astigmatism that is most likely not lens-induced.
Usually those are coming from high or moderate myopia.
Genetics, other influences not related to healthy attitudes will not be listed.
Let’s number the possible cases.

1. Eye misalignment: phoria, tropia (strabismus)
From quite a few cases really digged in, I couldn’t find people having strabismus and not having astigmatism. Eye default placement makes a substantial amount of corneal remodelling stimulus, because it happens at least for every sleep time and every time person closes his/her eyelids.

1a. High myopia esotropia strabismus or esophoria caused by LR-SR band thinning
Corneal remodelling mediators such as rectus muscles are simply off from their anatomical position and they gradually lose normal tones, resulting with over- and underaction of certain muscles.
I suspect to be the cause of my astigmatism if I indeed have this pathology.
If I have, muscle union surgery should fix my esophoria and astigmatism (gradually I guess and when I will not use cylinder).

The problem listed above also can strip off the ability of high/moderate myopes to do Active Focus, since there is no evidence extraocular muscles are not involved in Active Focus process.

2. Ciliary spasm
It does not exceed -1.50 DC. It should cease with cycloplegic drops instilled. If not, ciliary spasm could not be proven. As well, differentials of course will reverse both. There might be a possibility for this astigmatism to be in top of other.

3. Presence of ATRSA without correction
Against-The-Rule Spherical Aberration (ATRSA) is my term not used in research. Existence of it can be proven using n=1 experiment (myself). Not sure it is caused by eyeball optics or spectacles.

4. Functional Astigmatism
Dr. Forrest describes about this one. It is caused by tendencies of using some eye movements or unequal sight over the opposite becoming abusive in certain individuals.

References could be requested via replies.

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I’ve looked quite extensively into Dr. Forrest’s theory, I explained my case in detail in the 20/20 gains thread I made but basically after learning about it and digging in I found it hard to deny that my case nearly perfectly matches the hypothesis, I even noticed earlier today that even for tasks like cutting fruit I tend to put my hands more towards the right but keep my head still which had both of my eyes peer towards the right, making the left eye more susceptible to astigmatism which is my case, I made an effort to centralize the task as per Forrest’s recommendations for hopefully lessening it or even ideally completely reverse it.

As I’m also in the “non lens induced astigmatism” club I’m interested in these theories, the effect is significantly more bothersome than just regular blur because at least in my experience depending on what I’m looking at it can show up even in close up, the problem got worse last year after a few weeks of intense close up involving a lot of up down movement though at the time I didn’t know what astigmatism even is, I could just tell that things don’t look right, when I got my eyes checked (5 years ago) I was told I have it and it’s genetic so if that’s anything to rely on it didn’t entirely appear just last year, I suspect it either got worse or both got worse and slightly shifted axes, maybe my brain at that point was already half decent at cancelling all or some of it but the sudden change threw it all out of balance.

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Which is the case for my brain. All the crazy monocular and binocular eye checking one does with EM, has revealed some strange things. The first is that my mirror image oblique astigmatism is cancelled out quite well by the brain. The second is that the less myopic and less astigmatic right eye ‘takes on’ some additional astigmatism to make it easier for the much weaker and more astigmatic left eye to still make a decent contribution to stereoscopic vision. How I conclude this is by looking at the 6m Snellen chart without any correction. Binocular vision gives me a legible 20/20 in outside but not direct sunlight. When I close my left eye, the vision of my right eye goes all haywire, with various degrees of defocus and astigmatic deformation for the next 15 seconds or so while the brain sorts out the loss of the input from the left eye. When my right eye alone has sorted it out and can see 20/20 again and I then open my left eye, I can see 20/15 for about the same number of seconds until I am back at the initial binocular vision. Apparently stereopsis is worth the small sacrifice in visual acuity the right makes.

I can see some heads shaking. No, I am not imagining this effect, although I might misunderstand its cause. This is also why I recommend that one does not do monocular eye measurements by measuring immediately after closing one eye. It probably takes some time for the adjustment from binocular to monocular vision to take effect.

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That’s really interesting, I’ve noticed strange things happening as well, normally with binocular vision the astigmatism effect is there, sort of stacked and more concretely visible using the ring patterns or anything similar, the axes reveal themselves individually with each eye closed but also so do ghost images, left eye’s ghost image shifts to the left and a bit down and the right eye is more or less the opposite, together I see a subtle ghosted image going towards the bottom right-ish but it’s a lot more faint than when when I just use one eye. the effect is worst for me when I look at the DVR’s power LED which has a ring shape, if it’s completely dark I see several ghosted images, the bottom left and right ones and even one at the top right-ish, if I stare even more then more of their friends join in on the party, the true LED though is still obvious and doesn’t get lost in the ghosted images but it’s truly exacerbating nonetheless.

For the time being I can’t see the 20/20 line with either eye, it seems to be about OD: 20/40 and OS: 20/50 without me being generous with either the lighting or how much credit I give to myself for slowly becoming more acquainted with the letters and I use the 3m Snellen, not sure if it’ll be even worse with the 6m one but that’s something I haven’t the courage to test yet.

Beautifully said. I have a few full moons joining the party with my right eye, and many more with my left eye. However, in this case ‘the more the merrier’ does not apply.

It’s great to be able to keep a sense of humour about this mess. :smile:

Yeah definitely, it’s extremely annoying but hopefully it can be dealt with over time, I definitely want to deal with most or even all of the astigmatism first, ideally anyway.

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Good luck with that. I have found astigmatism particularly stubborn.

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I can’t be in comfort with toric contacts, so my astigmatism in a major pain in the …
I tried to go for glasses, but still too much uncomfortable.
I am sensitive to unnatural aberration, like chromatic.

I can guess my astigmatism will disappear after dealing with esophoria or performing surgery for extraocular muscles if they are malinserted.
The funny thing I can’t increase my astigmatism a bit even when trying hard to equalize eyes a bit. It is dumb the same, not increases or reduces by defocus. Only increased a bit on its own, but doubtful as different autorefractors say different. As well as test lens kits.

Jack Jakey made a video and post about corneal astigmatism.

His opinion is visual cortex compensating for corneal shape.
While it might be the case, but reversal of corneal irregularity is the most preferred way :slight_smile:

Fortunately, keratometry is very cheap and can falsify or prove Jack’s theory.

I think that theory only goes so far, most people have some small degree of it that is compensated for but if it starts going into the several diopters territory I think the eye actually has to change in some way, if I understood Forrest’s studies properly they didn’t find direct correlations between the keratometry results and the reductions or increases in astigmatism, that’s why there’s no concrete explanation in the papers for what exactly changes with the eyes but rather that eye movement has a hand in it and there were enough research cases to prove the hypothesis.

I interpreted Jake’s statement as him saying that your visual cortex will signal your eyes to change to compensate for the astigmatism rather than just ignoring it but I’m not sure, in any case if the eye can become astigmatic then we can hope it can also be reversed, the current mainstream accepted theory is everyone is born with it and then it regulates over time but there are many cases where it appeared later in life so that sounds half-baked as far as I’m concerned.

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Lens compensates cornea astigmatism up to 1.00x90 or -1.00x180 (Yee).
In other cases, only for 0.50 D (Ruban).
Compensation for oblique astigmatism is partial (My findings).
Compensation for against-the-rule astigmatism of cornea by lens is not possible (Yee).
Lens compensates corneal astigmatism by means of internal rectus muscle (Yee).
This compensation is possible due to difference in innervation of internal and external rectus muscles and that is the reason only positive vertical (negative horizontal) astigmatism is perfectly compensated (Yee).

Active focus might be in this mechanism of compensation: lens flattens a bit more, decompensating corneal astigmatism (because spherical equivalent decreases by about 0.25-0.50 D) but spherical error goes lower (yet cylinder increases). Both might be broken in moderate or high astigmatism (My findings): "Active Focus" on autorefractometer: astigmatism compensation?

A person with zero of corneal astigmatism is rarely found, if at all in each time of day (My findings).
Often, right eye has more average corneal power, more astigmatism and shorter axial length; and left eye has less average corneal power, less corneal astigmatism and longer axial length (My findings).

I use this trick to achieve the most clear vision without cylinder correction. I try each lens power between sphere value of sphere+cylinder correction and spherical equivalent value. I have the most clear vision somewhere in between. But if doubling is my primary concern, SE is definitely better (at the cost of lower visual acuity).

Mine is ATR but I can compensate for it to some extent via active focus, it’s much harder in closer distances and relatively easy for distance especially during the day, I remember reading that the astigmatism usually isn’t entirely corneal or lenticular and maybe sometimes the lens mimics the same angle of the cornea, though I don’t know how credible that is.

Merging the ghost images is hit and miss and usually it’s pretty hard, usually when I try to do it and succeed to some extent I feel a bit of pressure around my eyes, which makes me wonder if the extra-oculars are doing any work at that moment, it feels like it but I don’t know. I know the bates method people say it’s caused by irregular pull of the extra-ocular muscles and it sounds like it makes sense as the cornea rests on the sclera so it’s shape can theoretically be warped by irregular pulls of the muscles. In practice based on the specific exercises I’ve done so far short term effects are instantly noticeable with distant lights as the starburst effect lessens drastically, I already see small (seemingly) permanent changes but fair assumptions can only be made in the long run.

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I consider Bates exercises are for relaxing and not strengthening.

Myopia is asymmetrical condition, you need mostly to push accommodation the opposite way (by AF), because if you strengthen it on both sides, nothing is going to work.

I suspect your cornea has oblique astigmatism.
The only way to determine which angle you have indeed is keratometry.
You can find it if you have some papers from your optometrist by “R1 R2 CYL AVE” or similar text.

Yeah they don’t seem like they’ll actually cause any real changes, regarding the direction of strengthening that’s also why I think the tibetan eye chart didn’t do anything for me because I was moving my eyes in all directions, it did at least make me realize left/right is uncomfortable for me by comparison.

the checkup I got has 80 degrees axis on both eyes but that was 5 years ago, my own tests suggest OD: 100 OS: 80.

If for example cornea has 120 degrees and lens has 90, it could be like 100 in reality.
Or cornea 60 and lens 90, close to 80 then.

I guess ATR cornea ia very rare unless you have a work in which you constantly move your eyes up-down or you have high hyperopia or aging.

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This is exactly what I think caused it for me, I always had this habit of up-down eye scanning because of my weird posture but a thing I did a lot is looking up and down a lot when I was playing videogames, looking up at the monitor then down at the smaller screen or vice versa, I did it even more last year and about two weeks of doing that I noticed things don’t look right (less right technically) and now that I’ve learned some stuff that feeling was basically the astigmatism, probably getting stronger and maybe shifting axes a bit which threw off what my brain was used to and it became noticeable. I also seem to mostly be a head mover when I want to look left and right, left-right eye movement alone feels odd to me but up-down doesn’t, I’m still trying to figure out what’s going on but so far that’s what I’ve figured about my habits.

I only move my eyes up-down because I can’t move both eyes left-right to the edges without having double vision at the sides, or I move them left-right only gently and after some time of doing that they begin to look at bridge and they won’t return to divergence for some time.