Author Topic: Axis of astigmatism vs. head tilt  (Read 11222 times)

Offline lenmel

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Axis of astigmatism vs. head tilt
« on: March 04, 2015, 07:39:58 AM »
Hi Everyone,

I have interesting experience that could potentially help to better understand astigmatism.

When I tilt head left or right up to 45 degree, eyes compensate this tilt by intorsion and extorsion (I can see it in mirror). So with head tilt eyes rotates with respect to head but not with respect to place where I am standing/looking. This is normal, everyone should be able to experience it.
 
But I found very amazing fact that my axis of astigmatism changed approximately by same angle as head tilt. Rotation between eyes and world didn’t change but axis of astigmatism changed. If I had astigmatism caused by cornea, lens or even ciliary muscle axis of astigmatism should not change because cornea, lens, ciliary muscles and retina does not rotate with respect to place where I am standing.
 
I have 2 questions:

1) Does your axis of astigmatism change with head tilt (please do NOT use glasses)?

2) Do you have any idea why is this happening to me?

Offline Alex_Myopic

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Re: Axis of astigmatism vs. head tilt
« Reply #1 on: March 04, 2015, 08:33:19 AM »
Very good point lenmel!

1) I have diplopia (after reducing myopia) which I believe is astigmatism and yes on the astigmatism mirror I see the axis change even if I titl my head less than 45 degrees.

2)Dr Alex says diplopia after rehab is a brain issue and although the eye doesn't move in relation to the mirror the brain does.
« Last Edit: March 04, 2015, 08:36:13 AM by Alex_Myopic »

Offline OtisBrown

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Re: Axis of astigmatism vs. head tilt
« Reply #2 on: March 04, 2015, 10:01:16 AM »
Hi Lenmel,

I think astigmatism, that is less-than -1.5 diopters - is not worth "fixing".  Yes, I noticed this "rotation" that as I tilted my head, (rotation), both eyes would "stay level", like a gyroscope.

But I always verify 20/20, on my Snellen using a spherical lens.  Even if I did have slight astigmatism, I could see NO REASON, to ever "correct" for it,  since all astigmatism is "takes out" by our brain, when you view an object with both eyes open.

But your glasses (with the astigmatic cut), move with your head.  In me, this produced severe head aches.  After that I insisted on "spherical" lenses, (that would give me 20/20), and rejected any cylinder in my lenses.  That is exactly for the reasons you deduced.  So:

1) The axis of astigmatism, "moves" with your eyes.  Your lens (cylinder) correction does not.

2) It happens to everyone, not "just you".


Hi Everyone,

I have interesting experience that could potentially help to better understand astigmatism.

When I tilt head left or right up to 45 degree, eyes compensate this tilt by intorsion and extorsion (I can see it in mirror). So with head tilt eyes rotates with respect to head but not with respect to place where I am standing/looking. This is normal, everyone should be able to experience it.
 
But I found very amazing fact that my axis of astigmatism changed approximately by same angle as head tilt. Rotation between eyes and world didn’t change but axis of astigmatism changed. If I had astigmatism caused by cornea, lens or even ciliary muscle axis of astigmatism should not change because cornea, lens, ciliary muscles and retina does not rotate with respect to place where I am standing.
 
I have 2 questions:

1) Does your axis of astigmatism change with head tilt (please do NOT use glasses)?

2) Do you have any idea why is this happening to me?
« Last Edit: March 04, 2015, 10:05:58 AM by OtisBrown »

Offline lenmel

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Re: Axis of astigmatism vs. head tilt
« Reply #3 on: March 04, 2015, 11:40:53 AM »
Alex_Myopic:

Do You think that this can be more brain problem (the way how brain process image and then control eye) than actual eye problem (ciliary muscle "atrophy", ...)? I also often see double or more images but I didn’t find a way to fuse them in one clear image.


OtisBrown:

All observations were done without glasses. That’s not what caused this effect.

As you are saying eyes are gyroscopically leveling head tilt. But my axis of astigmatism is changing.


I have relatively mild myopia =1D and astigmatism =0.75D.  One axis direction is from center to left upper corner, second from center to right upper corner. Axes are mirrored by nose plane.

Offline OtisBrown

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Re: Axis of astigmatism vs. head tilt
« Reply #4 on: March 04, 2015, 11:54:33 AM »
Hi,

Otis> I know we will have a "difference of opinion" on this issue - but that is what we are here for.

Lenmel> As you are saying eyes are gyroscopically leveling head tilt. But my axis of astigmatism is changing.

Otis> I personally would have a very hard time judging if my "axis of astigmatism" changed with my eye tilt. I think most ODs would agree
with that statement, and would say that, since your eyes "remain level" your perceived astigmatism will always be related to your
eyes.  Therefore "rocking" your head (with no glasses on) should NOT change your value of astigmatism.

Otis> But why not post your current prescription, and visual acuity.  My refractive status is about +3/4 diopters, with no astigmatism,
that I care to measure.  My visual acuity varies between 20/15 to 20/20.

Otis> What are your interests?  Reducing your prescription?


Alex_Myopic:

Do You think that this can be more brain problem (the way how brain process image and then control eye) than actual eye problem (ciliary muscle "atrophy", ...)? I also often see double or more images but I didn’t find a way to fuse them in one clear image.


OtisBrown:

All observations were done without glasses. That’s not what caused this effect.

As you are saying eyes are gyroscopically leveling head tilt. But my axis of astigmatism is changing.


I have relatively mild myopia =1D and astigmatism =0.75D.  One axis direction is from center to left upper corner, second from center to right upper corner. Axes are mirrored by nose plane.

Offline Alex_Myopic

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Re: Axis of astigmatism vs. head tilt
« Reply #5 on: March 04, 2015, 12:19:41 PM »
@lenmel

Me too I've noticed the mirroring of my eyes astigmatic axes through the nose line and I think that's why with both eyes looking there is some correction in ghosting.

Moreover Mr Brown writing about the gyroscopic behavior of eyes and the problem with the astigmatic glasses, doesn't disagree with your previous observations he just points out that since astigmatic glasses don't rotate with the eyes then the error is becoming bigger if for example the problem is in the cornea or ciliary which both rotate.

Me too I find this problem complicated and like you I cannot fuse into one image yet especially when looking with one eye.
There must be a physical problem in the eyeball (like more flat meridians (after rehab)) so the brain tries to process the ghost image while maybe altering its position in relation to the head's rotation.

If you put some pressure with your two fingers to the cornea in an axis vertical to the astigmatism axis the you can almost counteract the astigmatism in any rotation so it should not be only a brain's problem.
Also if I look a spot led in total darkness the astigmatism becomes more apparent after a while with ghosting images. Why not immediately if it is only an eye problem?

At my 20/25 vision I feel my remaining myopia now is not so bad as my astigmatism!
« Last Edit: March 04, 2015, 12:23:24 PM by Alex_Myopic »

Offline lenmel

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Re: Axis of astigmatism vs. head tilt
« Reply #6 on: March 04, 2015, 01:26:44 PM »
OtisBrown:

I close one eye, look at astigmatism chart, see that most blur is oriented in diagonal line, tilt head by aprox 45 degree to right, blur changes to vertical line, tilt head 45 degree to left side, blur changes to horizontal line, tilt head back to normal position, blur orientation is diagonal again. It’s same with other eye only with switched orientation. Gyroscopical leveling of my eyes works well even with one eye closed. No glasses on.

It’s really bugging me.

My visual acuity hugely depends on light condition, it’s between 20/80 and 20/120. I have never worn glasses full time, only for driving, cinema and presentation. But last few years I see so badly especially at night, I am worried that I will have to wear glasses much more. It’s almost half year I started to follow main rules of better vision described by Todd, David de Angelis and others, but so far no significant progress.


Alex_Myopic:

You are right that with both eyes open I see much better because axes of astigmatism are almost perpendicular to each other and brain clears things up.   

Altering cornea shape by finger pulling/pushing around eyes helps, but it’s same effect as ‘temporal‘ Lasic which changes cornea shape.

I also see while looking at moon/spot light one main image and usually few others. After observing it for awhile main image usually clears up and the others become more blurry in axis of astigmatism. It is change in image I see, but overall quality of vision doesn’t improve. I see little bit better main image but blurry diameter around this image get worse/increases.

Offline Alex_Myopic

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Re: Axis of astigmatism vs. head tilt
« Reply #7 on: March 04, 2015, 02:19:26 PM »
In optics I can only imagine two images of the reality if one is "direct" and the other takes some power of the direct signal and depicts it through a prism. With cylinder glasses we can shrink and make less the distance in the ghosting lines in the astigmatic mirror so they appear as one.

My point is that since we have analog refractive distortions in one eye (no prisms in the eyeball!) and we and up in two images in ghosting, more like a digital signal error, so maybe the brain takes the analog distortion in the retina and makes two images.

We can make an ellipse look like a cycle with cylinder but I don't think we can make two pictures merge into one generally.

Offline lenmel

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Re: Axis of astigmatism vs. head tilt
« Reply #8 on: March 05, 2015, 01:11:57 AM »
Alex_Myopic:

People with corneal disease keratoconus often see multiple images. Their problem is caused by irregularities on cornea. With my experimentation with head tilt it’s seems very unlikely that keratoconus is my problem. In our cases multiple images might be caused by irregular lens shape. This irregular shape would appear only for far focus. There might be two ways how it works. First would be when center part of lens is more focused than outskirt of lens. That could cause clearer image overlaying blurry image. Second way might be in case when different parts of lens along axis of astigmatism have different focal points and that could lead to multiple images approximately along axis of astigmatism. 

Offline lenmel

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Re: Axis of astigmatism vs. head tilt
« Reply #9 on: March 06, 2015, 03:54:55 AM »
Tom:

I don't think that effect of gravity on lenticular astigmatism is strong because people tend to have almost randomly oriented axis of astigmatism.

We can see well at near distance (I can see clearly without astigmatism), so there is not fundamental problem with lens nor cornea. But I think that uneven relaxation/contraction of ciliary muscle might lead to lens astigmatism/high order aberrations during far focus. There are few rows of zonular fibers between lens and ciliary muscle. Ciliary muscle might relax/contract for example front rows more than back rows. This might cause center part of lens more focused than outskirt of lens or otherwise. Or ciliary muscle might relax/contract more/less in axis of astigmatism quadrants than in perpendicular quadrants. Or it might be combination of both. This is really speculation because no human/animal research was done on this topic. But this could be explanation of what I/we see.

Based on my observation with head tilt it seems that change of my axis of astigmatism and therefore change in ciliary muscle relaxation/contraction is based on head tilt and eye leveling. It might be that some brain neuro signals which should control only extra ocular oblique muscles (eye rotation) accidentally interfere with control of ciliary muscle. That might be brain adaptation for near vision. Once again it's speculation but so far I didn’t find better explanation.

Offline Alex_Myopic

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Re: Axis of astigmatism vs. head tilt
« Reply #10 on: March 06, 2015, 01:18:27 PM »
Another experiment I'd like to post which supports lenmel's above analysis about this type of astigmatism and diplopia-astigmatism after myopia rehab:

In a total or much dark room I saw with one eye one led of the tv which shows that it is stand by. In the beginning I see just one ghost image. After a while gazing it can appear more ghost images as lenmel described. Moreover if I start playing with accommodation for example gazing at nothing as if I was thinking something or look even further while the led is about 2,5m away, I can see these many ghost images going worse or better in relation to how correct I can accommodate! So this immediate relation to astigmatism and accommodation shows a very tight connection with the ciliary body and lens. If it was a corneal or eye meridian problem then why accommodation (which is controlled by brain) would play such a role? Wouldn't wrong accommodation just create blur and not ghosting? So there must be some partial wrong in controlling (or physical) the accommodation mechanism and that's why Mr Becker and others succed even with diplopia and Dr Alex says it is a brain matter and with time and no glasses it could be dealt.

Me too I see zero diplopia at near distance. Shouldn't be noticeable in very tiny letters if it weren't zero at near (if it were not a ciliary and lens problem)?
« Last Edit: March 06, 2015, 01:23:48 PM by Alex_Myopic »

Offline lenmel

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Re: Axis of astigmatism vs. head tilt
« Reply #11 on: March 08, 2015, 04:22:21 AM »
Alex_Myopic:

I have almost same experience. Looking at square led light in dark room. At the beginning my vision are in state A. I usually see one image. If I voluntarily unfocus (as I was looking at near or at nothing) this image evenly becomes unsharpened. Then I try to focus on led light (observing, slow smooth blinking) and my vision slowly changes to state B. I see ghost images. When I voluntarily unfocus I still see these ghost images but unsharpened.

The question is what changes between states A and B? Is it a change of brain processing of optic information or change of ciliary muscle function or something else? I don't believe that change of brain processing explains what I see during voluntarily unfocus during state B.


Tom:

You are right that larger pupil dilatation increase number of ghost images because light goes through bigger part of lens. This worsens perception of all eye defects on cornea, lens, ciliary muscle.       
   
You are also right about accommodation reflex with pupil constriction. But I think this is not main factor for not seeing ghost images at near distance. I can give you 2 reasons:

1: I can see ghost image (sometimes two) even during bright day. One of main factors of seeing ghost images is contrast. Higher contrast more ghost images. Led lights vs. dark panel, cable wires vs. sunny sky.

2: Distance where ghost images start to appear is almost same as my edge of blur distance. Sometimes little bit closer, sometimes little bit further. I don't think this is coincidence.
     

Offline lenmel

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Re: Axis of astigmatism vs. head tilt
« Reply #12 on: March 09, 2015, 12:09:12 PM »
Tom:

I don't know exact cause of my diplopia but I believe it has same cause as my myopia. Because I can modify my diplopia/myopia by intensive observing distant objects, by slow easy blinking, by relaxing eyes, I believe this change can be caused only by changes in something I/my brain can control and that's muscle function in eyes (ciliary muscle) or around eyes (extraocular muscles). It seems that this is similar experience as Milos mentioned in comment you found out.

Considering my observation with head tilt/eye rotation it seems that extraocular muscles have direct effect on my axis of astigmatism. On the other hand when I look up, down, left or right I observe no change in vision nor change in axis of astigmatism.

It seems that most people believe only in plus lenses and reducing near accommodation time and reject function of extraocular muscle in accommodation. But for example David de Angelis extraocular exercises helped some people who failed with only plus lenses.

What is your thought on this?   

Offline lenmel

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Re: Axis of astigmatism vs. head tilt
« Reply #13 on: March 11, 2015, 11:48:05 AM »
Tom:

Thank you for this information and links. I have read many studies and I have many more to read. I know eye is really complex and complicated with many positive and negative feedback loops. And there is a lot we don't know.

Many of these studies found very small differences for example in axial length and suggest theory what could in long time lead to myopia. Some of them contradict each other. Some of them seem to be logical. Some of them might be right.

Unfortunately so far I didn’t find study which would explain the question in my initial post in this topic: Why head tilt by angle alpha causes change in axis of astigmatism by angle alpha.

Best study on this topic I found:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3928831/

Based on this study and my observation I have very good "ocular counter-torsion compensation" and therefore I should have stable axis of astigmatism. But that's not true.
 
I excluded interfering effect of eye lid on cornea by opening my eyes wider and looking straight. It made no difference.

Offline Alex_Myopic

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Re: Axis of astigmatism vs. head tilt
« Reply #14 on: March 12, 2015, 04:30:59 AM »
So with Tom's reference about vitreous chamber elongation, a book stand on our office might help reducing downward convergenve because with look upper with this way (also helps the neck).
I remember myself developing an eye floater after a period of much study and being overanxious.

There are some claims about extraocular muscles and astigmatism. Some say that when we read we move our eyes in one deriction so that's why we have a common axis on astigmatism. Others advice exercises on a vertical to reading axis. added with plus lense I'm doing such a special program and started feeling improvement in diplopia. If I confirm with Snellen I'll report.

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