Wednesday, January 22, 2014

#220 session: what does it mean to have good binocular posture?

I've made a few minor changes to the routine.

I adjusted the anode positions a little so that they're pretty close to one another.  Before when I was looking at the o1 and o2 positions according to the 10-20 system, they appeared to be farther apart than they are.  Now I think the positions are more accurate.
File:Poles of cerebral hemispheres animation small.gif\

Also, I've been thinking and contemplating a bit more about what it means to have good binocular posture. When I began vision therapy (after a year of 'vision therapy' with my 'vision therapist') I was really clueless about the visual system and needed guidance desperately.

I came across some papers written by Fred Brock where he was talking about binocular posture.  What I got out of it is that the eyes need to be able to rest in place comfortably and naturally.  But it wasn't detailed, and given that I knew very little about the visual system it wasn't as helpful as it could have been.  

Now I understand quite a bit more about the visual system, some of its adaptations, and most notably the relationship between accommodation and vergence.  I understand the visual system a lot better by doing research, talking with people with strabismus, and by doing feedback exercises.  Especially by doing feedback light tube exercises, I've been able to see and experience the theory firsthand.

As I said before, a few years ago I was clueless about the visual system and as a result my exercises were very ineffective.  I had this idea of 'reverse engineering' the problem.  I was fixated on the idea of correcting the alignment of my eyes, particularly fixing the hypertropia on the left eye since it was the most obvious thing.  The rationale was that if they eyes aren't aligned, nothing else would work so I needed to fix the alignment before anything.

I spent about six months doing Mardsen Ball, bar reader exercises, and walking around with a bar prism base up.  I would use the prism base up to cause the left-hand double image to go downward even more than normal.  Then I would have to correct the double image by pushing it up by pushing the eye down more than it would normally have to be (without the prism) to keep the eyes vertically aligned.  The idea was to somehow get the hypertropic eye 'stuck' more downward so it would line up with the normal fixing eye.

I got nowhere by doing that.  That was a pretty low point for me.  Actually, it was hell.  I was demoralized because I'd already spent $7,000 on a vision therapist, done hundreds of hours of vision therapy during that year, and had nothing to show for it.  Now, the things that I'm doing on my own don't seem to work, and I have no idea what the hell I'm doing--worse, I was becoming convinced that no one else did either.  And yet, as much as I wanted to, giving up wasn't an option.  The confluence of desperation and my unwillingness to give up had me teetering on the edge of insanity.

The turning point for me turned out to be the light tube, which was introduced to me by Heather.  As I've mentioned in previous entries, when you look into the light tube, you'll see a single glowing circle, colored depending on what kind of filters you're using.  I found it useful because it provides you with simple input, and so it allows you to be aware of what's wrong with your visual system.

By doing light tube exercises, I became much more familiar and intimate with the visual system.  I became much more aware of the relationship between motor fusion and sensory fusion.  For instance, I noticed that by having a good workout that focused on motor control I would automatically have less suppression (because improved motor control will result in less visual conflict).  And less suppression can help with motor control (since less suppression forces you to pay attention, and thus, avoid visual conflict with consciously controlled motor movements).

I learned how to control the different components of my visual system.  I could move the double images in any direction relative to one another.  But I would focus on trying to superimpose them (because that's how a binocularly normal person sees).  I could accommodate each eye individually.  I could even control suppression by focusing on making the entire scene as bright as possible.  I figured out that by doing this, I'm causing summation to occur--that is, I'm combining the input of both of the eyes into the brain--'unsuppressing'.

I became very familiar and intimate with the accommodation reflex.  This refers to a built-in reflex in which accommodation and vergence are linked together, and thus, when you accommodate, there is going to be a corresponding change in the vergence of the eyes.

Accommodation is the focusing mechanism in the eye.  When light rays pass through the lens, the lens bends those light rays toward one another to a focal point.  The goal of accommodation is to make sure that the focal point stays on the retina.  When an object you're looking at moves farther away, the focal point tends to move inside the eyeball.  To accommodate for that, muscles pull on the lens to make it thinner, so that the lens bends the light less so that the focal point is able to stay on the retina.  Keeping the light rays converging on the retina is what enables us to experience a sharp, in-focus image regardless of how far away the object is. The lens is accommodating for an object's changing distance.

On the other side, you have vergence, which refers to the ability of both of the eyes to point at the same spot in space.  When you look at an object close to you, your eyes converge together, and they diverge when looking at an object farther away.

So you have two things that happen when you change focus to something that's near you.  The lens becomes thicker to increase the lens's ability to bend light rays, and the eyes turn in toward one another.  This is a reflex and it happens automatically.  When you thicken your lens, you're automatically going to converge your eyes.  This reflex is why an accommodation insufficiency can cause an eye turn.  The brain tries to get the input of each eye in focus, but can't because of an accommodation insufficiency so it tries to give it more power.  That extra power does nothing because of the accommodation insufficiency, but the other part of the reflex, vergence, does respond, and the result is mis-convergence.  Accommodative esotropia is a common example of this.

One of the problems that I noticed with the light tube is that the accommodation of my two eyes is out of sync.  I've referred to it as the 'accommodation out-of-sync' problem.  I can get each of the double images to come into focus, but not simultaneously.  When I get one in focus, the other gets out of focus, and vice versa.

Later on I realized that I could actually get both of the double images in focus, but only by either overconverging or overdiverging--that is, I could accommodate both of them, but only if I mess up vergence. What the hell?  Of course, I figured it out.  It's because of the accommodation reflex, and the fact that I've never used my visual system in a binocular way.  So in hindsight, it makes sense why these different pieces would not all be on the same page with one another.  It's a matter of fixing the calibration so that I can fuse while accommodating with both eyes.

I did some weird stuff to tend to this.  I made up some weird light tube exercise that I called the 'fudging method' where I would accommodate both of the double images, keep them accommodated, and them pull them toward one another. It proved very difficult, but I think it helped a little.   It was very straining to try to get everything accommodated and singular.

Later on, I decided to get contact lenses, and that actually helped quite a bit.  It turned out that I had some small astigmastism on the left eye and small myopia on the right.  That, and continual light tube exercises, and understanding the components of my vision resulted in this accommodation out-of-sync problem going way down.

It was around this time that I started putting load on the light tube exercises by incorporating movement.  I would do that while providing anodal stimulation to my occipital poles (o1 and o2: Google '10-20 system').  By doing this, I'm able to focus on sensory fusion and motor fusion simultaneously: sensory fusion by making the scene bright, and by squashing the accommodation out-of-sync problem; and motor fusion by paying attention to the feeling of the muscles as I make movements and trying to avoid ghosting and trailing of the lazy-eye double image.  I find this, especially with tDCS, to be very effective.  This is because I've learned about how motor fusion and sensory fusion affect one another.  So if you can attack both simultaneously the workout is going to be that much more effective.

Since the accommodation out-of-sync problem is now so minute, I'm able to superimpose the double images and get very close to perfect accommodation on both eyes.  There is a little bit of blurriness when I move my head because when I do that, my eyes have to re-adjust and re-accommodate (nice loading trick).  I noticed that as I get closer to perfect accommodation with both eyes, I get much closer to fusion and the ghosting and trailing is going way down.  There is less preference for one eye over the other.  My awareness, or the I, is shifting from being behind my fixing eye to being somewhere between the two eyes.

I think this is related to my accommodation out-of-sync problem going away.  This is because when you pay attention to something, you automatically accommodate your eyes for that thing you're looking at.  Attention and awareness is tied to accommodation.  Now that I'm starting to have proper accommodation, the way that I experience awareness is changing.  And also, now that my accommodation is becoming properly calibrated my motor ability of the 'lazy' eye has gotten much better.  You can't have proper motor ability with both eyes unless both eyes are accommodating to the best of their ability.  If you're not accommodating properly with both eyes you can't pay proper attention through both eyes, and if you're not doing that, you won't be able to have perfect movements.  All of these different mechanisms are tied to one another.  Having good binocular posture means having all of these mechanisms calibrated and all on the same page with one another.

I had a conversation about vergence and accommodation with Michael Lievens.  He said that he believes that this is a problem that most strabismics have.  It makes sense why this would be true.  Actually, it would be a really weird stroke of luck if everything was in perfect sync for someone who never used his visual system in a binocular way.

There are two girls from a strabismus group on Facebook (DIY Vision Therapy for those who may be interested in joining).  They're both able to straighten their eyes, but when they do that, they can't see anything.  When one uses glasses, she's able to see, but then the eyes cross.  The other girl has the same thing, but she's able to do it without glasses.  It looks like the same issue.

I'm not sure how to fix it, but if they are able to fix it, they're going to have to figure out a way to override the accommodation reflex.  It's easier said than done, but it can be done.  After all, having success with those hidden autostereograms requires it.  It requires that you diverge your eyes as if you're looking through the page, and it requires that you accommodate your eyes on the page.  The reflex has to be overridden for it to work.

My guess is that for most strabismics to gain stereopsis, this has to happen.  It's not enough to have both of your eyes pointing at the same spot in space.  They have to do that while at the same time accommodating to the best of their ability.  And for most people, they're going to have to calibrate the vergence/accommodation reflex.  It's just tricky though, because for one of the girls that I was talking about--she said that when she has her eyes straight, she can see nothing.  When she sees clearly, her eyes cross, and she has no control of vergence (I asked her).  I suggested controlling vergence while accommodating can be something for her to learn how to do.  It was suggested by others that she might lower her prescription as a way of dividing the problem in two so that she can perhaps half-accommodate, get some modicum of vergence control, and then build on those abilities.  I'm not sure exactly how to do it, but it's clear that the reflex has to be calibrated and this is an issue most strabismics will face when attempting to gain binocularity.

I'm now very close to fusing, and I think I will gain stereopsis soon.  Looking back, I now understand why I had such a difficult time with vision therapy.  Before I was obsessed with the lazy eye's alignment, trying to force it around as if it were an external object.  But it's not an external object, and the problem is not mechanical.  It's a problem of wiring and integration.  When I started to understand the system I began devising exercises that focused on motor and sensory fusion.  I also learned about the importance of having a properly calibrated accommodated reflex.  As my new exercises caused the lazy eye to become integrated, I noticed that the alignment was gradually fixing itself (I take pictures of my eyes roughly every three to four days).  At the same time, I started noticing myself as being behind both eyes more, and I began noticing more 'pop', and depth.

Heh, three years later.  I wish somebody were there to tell me these things years ago.  It is my hope someone can relate with this information, and perhaps find it to be intelligible and useful.

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