Wednesday, March 30, 2011

Just a little

I saw a little depth at my last vision therapy appointment. For the first time! Just a little! But still... it happened! Here's the story...

In Effective Strabismus Therapy, Dr. Israel Greenwald talks a lot about working with strabismus patients to achieve red/green luster while looking at a white wall. The patient wears red/green glasses, stands up close and stares at a big empty while wall, and tries to make the colors intermix and become inseparable. To help achieve this, he recommends that the patient wear high plus lenses (+15 to +20). These high plus lenses are basically superpowered magnifying glasses that make everything blurry. This removes all figure/ground distinctions and allows for easier fusion.

I asked my vision therapist if we could get some high plus lenses and she said 'Sure!' She called in an order to the lab, and I thought everything would be fine. It turns out, though, that it's very hard to find a place that even makes plus lenses that strong. The strongest that I have seen available for order on the internet are +12. (+12 is actually very strong though and would probably work, but that's not part of the story.)

So last Friday, I brought up the topic of plus lenses again and my vision therapist had an idea. There were lots of contacts in the office, so why not try high plus contacts? That way, there wouldn't even be a chance to "peek around" the glasses and ruin the blurring between figure and ground. They weren't any +20, but there were some +6 available. (or maybe they were +4, I can't remember).

So I said yes, even though I was kind of terrified. (You remember what happened last time someone got all up in my eyes.) And it turns out, contacts are really hard to get in! I did the usual - hold your eyelids down like they are trying to escape - type of thing, but then I would involuntarily try to shut my eye so hard that my eyelids would turn inside out and block the contact anyway. It was both funny and gross.

20 minutes later, when they were finally in, I got to experience the world as myope (near sighted person). I actually found it quite nice. My eyes couldn't focus on anything and thus didn't try - it felt rather relaxing. It also blurred out everything past my nose, leaving me encapsulated in a blurry womb. I've always been an anxious and shy person, wondering what people are thinking about me (are they looking at my crooked eye??), and for once, I couldn't see anybody's faces. I just had to assume that everyone was smiling at me. I wouldn't want to live with uncorrected blurry vision, of course, but it was nice to take a vacation in blurry land for a while.

So we tried some red/green luster with the white wall, and the extra plus seemed to help (more plus would have been better, though). While, the contacts were in, we also tried some other things. I had some vague memories of reading that dim light can help fusion and help break suppression, and something about contrast levels.... and something about ARC and peripheral fusion... and something about something else... So we decided to try out some polarized vectograms while I was wearing the plus contacts, just for fun, and.... something happened!

First, I was looking at this "figure 8" vectogram:

I was looking at this one the previous week, and while rocking side to side, I noticed that one of the little triangles was moving with me. It only did it for a second, and I couldn't really get it to happen again, but I knew that this vectogram was doing something funny to my brain. So, while wearing the blurry contacts, I decided to start with this one.

I put the polarized glasses on and started to rock side to side like last time. And suddenly little triangles started popping off the screen! They didn't stay popped out for very long, but it happened more than a few times, especially (for some reason) on the triangles on the left hand side of the picture.

It reminded me of those pop-up story books - the kind where you pull a tab and little paper figures extend off the page. It was as if someone was pulling a tab behind the vectogram and making the triangles pop out. At one point, I even saw a wave of depth undulate across the vectogram and then disappear. It was pretty neat.

Excited, I tried another vectogram - the one my vision therapist calls "creepy clown."

Again, something happened! Nothing really popped off of the screen, like those little triangles did in the figure 8 vectogram.. It was more like... the screen fell away and I was looking through a portal into another dimension... A dimension of scary living devil clowns!

The area with the most depth was that area between creepy clown's legs, where you can see his two legs, his hand, and the stool. It's was very depthy in there. And yes, I do appreciate how creepy it is to have one of my first experiences with depth involve looking between a clown's legs. Some optometrist out there sure has a sick sense of humor.

Also, every time the screen fell away and got depthy, I got the strange sensation that someone was punching me in the stomach. That was pretty neat, too.

So that's the story. It wasn't in "real life", and it was blurry and unstable. But it HAPPENED. Up until this point, I have been secretly fearing that maybe I was born without those special binocular neurons. Maybe I became strabismic because my brain was missing some pieces... Now I know that's not the case. I just need to keep practicing.

Monday, March 21, 2011

What is "fusion"?

I'm writing this entry to describe my experience with "fusion" in vision therapy. I'm putting "fusion" in quotes, because I'm still not quite sure if what I am experiencing is fusion, or even what the definition of fusion really is. I know that, basically, fusion means two eyes making one picture. But what I've seen and noticed seems much more complex, and involves brain processes that I can't even begin to understand. In any case, this is what I have noticed about fusion so far...

First, I have noticed that fusion is not just one process. There seem to be several "types" of fusion that I have come across, and even within these "types", lines get blurred and things get murky. These types may even exists on a continuum. However, I will try my best to explain what I have experienced. Here are the three types of fusion that I have come up with:

1. Cut and paste
 This is the easiest kind of fusion for me. The images from each eye are selectively cut and pasted together into one image through some brain photoshoppery. An example of this would be the anti-suppression playing cards that I love so much.

When viewed through red/green(blue) glasses, these are the images that the brain must combine:

How does the brain do this? In my subjective experience, it feels as if my visual system is using scissors and glue to make a sort of collage.

Of course, it doesn't look like that. But it feels as if that's the process that my brain is going through - choosing the important elements from each eye, and deciding which to use in the final "collage." If the brain did not go through such a process of defining importance and cherry picking input, then what would stop the brain from making an image such as this?

The brain would not make the above picture, and one would never see the cards all blank like that. I dare you to try! The brain looks for meaningful input, and assembles everything together accordingly. That is why, when making anti-suppression activities, I am always writing letters on everything. I have learned from the playing cards that the brain cannot ignore letters.

For me, this type of fusion becomes more difficult as finer and more precise "brain cuts" and "brain pastes" are required. For example, fuse - by convergence or divergence - the image below:

What you should see is something like this:

This is quite hard for me to do, and I believe I know the reason why. Look at all of the places where the lines are in conflict (in pink). This would require some very creative cutting and pasting.

In fact, this comes close to requiring the brain to create a completely new image (rather than a collage), which brings me to the next kind of fusion.

2. Transmutation
In this type of fusion, something new is created that neither eye can see alone. This is not a composite of two images, as is the case with cut and paste fusion. Two images are combined in such a way that they create a new, unique third image.This is certainly not a collage. It's a new painting!

An example would be the "luster" effect. By convergence or divergence, fuse the two images below:

What you should see is one grid in the middle, with the red square and the yellow square magically transmuted into a new color. This new color was not perceived by either eye, it was created in the brain. (I imagine it will be glowing like it's fresh out of a nuclear reactor.)

This type of fusion is exceedingly difficult for me, and I'm not sure that I have properly achieved it. When I try to do luster activities, I tend to get flashing, alternating between colors, rather than the creation of a new color. I also imagine that stereoscopic vision requires a great deal of transmutational fusion, and thus it is very important that I get better at it! I can't be satisfied with merely cutting and pasting; my brain needs to learn how to blend and create.

3. Stereopsis
What happens here? I'll let you know when I see it. I've heard that salads, tomatoes, horse skeletons, steering wheels, and coat sleeves all start jumping out to say hello. It sounds pretty awesome.

Thursday, March 17, 2011

My left eye - a VT update

(I've lost track of the weeks. They're just flying by!)

The theme for my vision therapy lately has been "back to basics." My vision therapist and I were talking, and we decided that we skipped over some important stuff in the beginning. With new patients, she normally starts out with a lot of monocular patched activities, tracking, pursuits, body bilaterality, and so on. But in my case, I was very eager and kept being like, "Wow! Is that a cheiroscope? I read about that. Can I take that home?" And so we got a little ahead of ourselves.

As I've been progressing and starting to really get a feel for my eyes, I've been realizing the importance of those beginning foundational activities. I'm becoming very aware of how unequal my eyes are, and I can see how much of a hindrance that can be. Therefore, for the past few weeks, we've been going back to those basic beginning activities.

Specifically, I've been working on my left eye - the amblyopic and frequently turned eye. Here is what I have noticed about it:

1. It is terrible at pursuits, especially going from right to left. It prefers a quick succession of saccades, or what Dr. Len Press told us are "catch-up ballistic saccades." My eye thinks that it's tricking me with these saccades, and that I won't notice that they aren't real pursuits. You're wrong, eye!

2. It has trouble knowing where it's pointing. I sometimes think that I am using the center of my eye to track something, but really I have stopped moving my eye (because the object has moved to a place where it's hard to move my eye smoothly) and I'm just seeing it my peripheral vision. My eye feels like that is "good enough" and doesn't realize that it's not even tracking anymore.

3. It doesn't like to initiate movement or be the leader. It just wants to follow what my right eye is doing.

4. It has trouble maintaining a stable gaze. When I try to fixate on something for more than just a second, my eye jitters around the target. I've witnessed this using the MIT and seeing the Haidinger brush dance around the target that I was (trying to) fixate on.

5. It's even nystagmus-y on occasion. Sometimes when I wake up in the morning and my right eye is occluded by the pillow, I will look at the alarm clock with my left eye and the image of the clock will jerk back and forth over and over.

(and I'm sure I'll discover more as time goes on)

Amazingly, I had no awareness of any of this until very recently. How could I not notice all these years?

Now that I have noticed, I have been busy working away on my monocular skills with activities like:

tracking / pursuits with the monster
word searches with progressively smaller letters
marsden ball tracking
MIT mazes
tracking while keeping something in a circular afterimage
and so on...

And of course I've been throwing in some physiological diplopia and antisuppression exercises, because life would be boring with without them.

Monday, March 14, 2011

Thoughts on esotropia (and scotomas)

Sometimes, I lay awake at night, thinking of esotropia and how mysterious it is. I've read and heard over and over that exotropia is easier to treat than esotropia. Good thing I'm exotropic, I think to myself. But then I remember that I used to be very esotropic. I was a cross eyed baby! I had congenital/infantile esotropia. That's how this whole strabismus mess started.

I developed exotropia after my first surgery, and then a second and third surgery couldn't get rid of it. Is it really true that, because my strabismus surgeries accidentally made me exotropic, I now have a better prognosis than my esotrope friends? Even though my original condition was esotropia? That seems weird to me. Or lucky. Or something.

Perhaps it's all a mystery, and nobody knows...

After my previous post on suppression scotomas, I got interested in drawing out the suppression scotomas of esotropes. So here goes.

Both eyes are able to see the diamond, one centrally and one peripherally, and double vision should result because the eyes are not aligned. However, only one diamond is seen, because the peripheral diamond image is falling on a suppression scotoma.

In my previous post, I also mentioned that I had a habit of peeking around my suppression scotoma by overconverging. Is it possible for an esotrope to peek around their suppression scotoma? Yes!

If both eyes overdiverge and fixate on a point behind the diamond, that would make the diamond image fall outside of the suppression scotoma (and the image would double). However, this is easier said that done. I have trouble diverging my eyes at will, and I can imagine that an esotrope would have the same difficulty. After all, if they could diverge their eyes like that, they wouldn't be cross eyed! So it's possible that this may not happen as often.

It does explain something interesting, though. I am an exotrope, and I have trouble with physiological diplopia in front of the image I am fixating on. This is the kind of diplopia that happens when you put a pencil in front of your face, and make it double while looking at your professor. And when looking at the Brock string, I tend see an upright Y. I have trouble making the strings double in front of the bead. In both cases, the problem is the same: difficulty doubling in front.

My blogger friend Lynda, an esotrope, has the opposite problem. She has more trouble causing objects behind the image to double. While looking at a Brock string, she sees an upside down Y. She has trouble making the strings double behind the bead - difficulty doubling behind.

Both of our problems can be explained by looking at our suppression scotomas. As an exotrope, overconvergence causes images to fall outside of my suppression scotoma, and diplopia behind the fixation object is easier.

As an esotrope, Lynda would be the opposite. She probably has an easier time seeing diplopia by overdiverging, and thus seeing a double image in front of the object.

In conclusion, suppression scotomas explain everything in the world.

Thursday, March 10, 2011

Better training mazes for Macula Integrity Tester

(Well, better according to me!)

The Macula Integrity Tester (MIT) is vision therapy device sold by Bernell. Through a phenomenon called "Haidinger's brush", this machine allows you to see exactly where your macula is pointing. When you look into the machine, you see the small Haidinger brush spinning at the exact spot your macula is pointing. It's pretty cool!

The MIT is usually used for treating eccentric fixation (a subject for another post), but I like to use the MIT for general eye control exercises for my jerky left eye. If the Haidiner brush jerks and jumps around, I know that my eye is doing the same thing. If it moves smoothly, I know that my eye is moving smoothly, too.

One activity for the MIT are these training mazes. You look into the MIT and move the Haidinger brush through the maze. For my purposes, I try to make the Haidinger brush move as smoothly through the maze as possible.

I don't really like the mazes that are available, though. They are what are know as "perfect" mazes. They have one and only one solution, and many dead ends.

A maze of this type offers a task: find the correct way out. However, it's not a difficult task and it's often too easy to see the solution. Very few, if any, of the dead end paths of the maze are ever actually traversed, and thus most of the maze is not used. Imagine you were going through this maze and you got to that branch right before the exit. Would you really ever say to yourself, "I see the exit right there, but I wonder what will happen if I turn left and explore this bit over here?" The maze appears to offer a good opportunity to practice eye tracking, but the activity is over too quickly because, again, most of the maze is not used. The maze doesn't deliver what it appears to promise! I would even find myself pretending to get lost in the maze and going down obvious dead end paths, just because I wanted more practice with eye tracking. But I don't want to pretend anymore! I want a better maze!

So I took an hour, played around with a maze making program called Daedalus, and came up with some better mazes. They are "unicursal" mazes, meaning that there is one path through the maze with no branches. Thus, the entire maze must be traversed in order to complete the maze. Every inch of the maze is used! Below is an example of an 8 x 8 maze, the same size used in the original maze above. See how much more eye tracking is required in the new maze? If you quantify it by distance traveled, here is the score. Old maze: 21, New maze: 64.

Compared to perfect mazes, unicursal mazes offer an opportunity to practice eye tracking at greater length. Some might say that I killed all the fun and interest of the maze by removing the "find the solution" element. However, my feeling is this: you can solve mazes any time you want, but you only get so much time to practice fixing your eyes with your optometrist's fancy expensive machine.

I made 8 mazes with increasing levels of complexity. To use these mazes, simply open the .pdf file provided below, print the mazes onto transparencies, cut them out, and throw them in your MIT (because everyone has one just lying around their house, right?). Enjoy!

Unicursal training mazes for the Macula Integrity Tester

Wednesday, March 9, 2011

Finding the midline

Strabismics have problems keeping their heads straight. I have talked about this before, and so has Lynda. We are forever tilting our heads.

I think it has something to do with how we internalize our midline. If you ask someone where the midline of their body is located, they will draw a line down the middle of their body, from nose to belly button. Both strabismics and non-strabismics know objectively where their physical midline is located. But in everyday life, strabismics tend to operate from where they subjectively feel like their midline is.

It's my theory that your subjective midline is determined by the center of your visual field. Normal-eyed people have a unified visual field, and the center of that visual field conveniently lines up with the center of the body.

Strabismics only use one eye, and the center of that visual field becomes their subjective midline. Unfortunately, their subjective midline doesn't line up with their actual midline. The strabismic operates from what feels like his midline, and the result is head tilting and weird posturing. A stabismic may appear as if he has angled himself oddly to look at you, but he has really only centered you in his visual field.

This may also explain why I am duck-footed. I'm an alternating strabismic, and my feet have pointed outward toward my two alternating midlines.

As Dr. Getz explains in Strabismus and Amblyopia, "The problem of strabismus is not strictly an ocular or eye muscle control problem. Most strabismics are strabismics from head to toe."

Tuesday, March 1, 2011

Suppression scotomas - and why I overconverge

Suppression scotomas... I've read about them before, but I didn't really find the subject all that interesting. There's a spot on your retina... where you suppress... or something... blah blah blah... who cares. It didn't really interest me. But last night, while doing my vision therapy homework, I suddenly understood suppression scotomas. And I also realized the reason why I often cross my eyes and overconverge when I'm doing vision therapy exercises.

First, what the heck is a suppression scotoma? A scotoma is an area of your retina where images are suppressed. If an image falls on a suppression scotoma, it is suppressed.

This is me, looking at a diamond. I can see the diamond just fine in my right eye. My left eye is being bad, and shooting off into nowhere. The diamond can still be seen peripherally by my left eye, though, and thus I should see two diamonds. But I don't see two diamonds. I only see one diamond. Why? Because the diamond image from my left eye is falling on a suppression scotoma.

The suppression scotoma is that big green spot. Everything that falls on that green spot is suppressed. This suppression scotoma has been custom made by my eyes and brain to prevent double vision. It perfectly fits the way that I use my eyes in every day life. Things in my central field of vision are suppressed, yet things in my left-hand peripheral field are still visible. I do not experience diplopia.

When I do vision therapy exercises, I desperately try to see the input from both eyes, but I have trouble because there's a big scotoma in the way. I need to break down that scotoma and start using that spot on my retina again. But sometimes... I cheat. I peek around the scotoma. How do I do that? Overconvergence!

In this picture, the dotted lines show where my eyes are pointing. They aren't pointing at the diamond, they are pointing in front of it. This causes the image of the diamond to fall outside of my central vision, and I see two diamonds. More importantly, it causes the image of the diamond to fall outside of my suppression scotoma. I receive input from both eyes (hurray!), but it's a diplopic, misaligned image (boo!). I believe this is why, when doing activities with the red/green glasses, I often see a misaligned image like this:

When I realized that I had been overconverging to peek around my suppression scotoma, I was amazed. Brains and eyes are so smart. And tricky. And lazy. And good at finding shortcuts.