Physiological diplopia (and a fun exercise to practice it!)

Physiological diplopia (phys dip) is "a normal phenomenon in which objects not within the area of fixation are seen as double" (source). When someone with normal vision focuses on an object, everything in front of the object appears double, and everything behind the object appears double. This usually goes unnoticed by most people, unless their attention is brought to it.

Interesting side note - if you google "physiological diplopia", you find that many people have accidentally noticed their physiological diplopia, become incredibly concerned, and posted on internet message boards looking for a cure. Here's an example:

I only just found out there is a name for my double-vision, "binocular-diplopia". I am 17 years old and all my life have had a double-vision thing going on with my eyes. I didn't realise there was any problem until I recently looked into it online, discovering the description of this problem fits the description of diplopia. If I cover one eye, it goes away. This goes for both eyes. When I focus on an onject I see it as one, but whatever is behind it it doubled. What I need to know is how serious this can be for me... I have had no previous medical problems with my eyes, or with my head at all, so it has not been caused by any kind of tumors, etc. Basically i'm not sure what to do about this, I haven't told my parents about it. Should I see an eye-doctor of some kind? Please guide me on what I should do...(source)

I've also read that it's not uncommon for ophthalmologists to get a few patients like the one above in their offices from time to time.

Physiological diplopia differs from pathological diplopia. Pathological diplopia is diplopia that results from an abnormality in the visual system, such as strabismus. When someone with strabismus complains of double vision, it's because their eyes are misaligned and pointing in different directions.

If you have strabismus, you don't have physiological diplopia. It takes two eyes pointing at the same thing, and not suppressing, to get physiological diplopia. For a strabismic, developing the ability to achieve and notice physiological diplopia is a great thing. Why? Because physiological diplopia is an excellent way to determine if one is using both eyes, and pointing both eyes at the same place.

This is why we use the Brock string. The Brock string is a physiological diplopia exercise. When you fixate on a bead on the Brock string, the string doubles in front of and behind the bead. It forms an X. This is the normal response that we strabbies are trying to achieve.

I mentioned in a previous post that I had a little trouble with the Brock string. Instead of an X, I would see a Y.

I could see the double image behind the object I was looking at, but I would suppress the double vision in front of the object and only see one string. With practice, I got much better at seeing the X. However, when doing less controlled physiological diplopia activities, I was still terrible at it.

Hold your finger in front of your face. Look at your finger. Your finger should be in focus, and objects in the background should appear double. This has always been pretty easy for me. It's the next trick that is really hard.

Hold your finger in front of your face. Look past your finger, and look at something on the wall. If you do it right, your finger will double. I can't do it, though! It's too hard!

So, I have invented an exercise to help me practice physiological diplopa in free space. My vision therapist really liked it, so I decided to share it. Here it is!

Josh's Special Red/Green Diplopia Exercise of Fun

First, you need targets to fixate on, and the targets must be able to cancel with red/green glasses. Why? Because then you will know for sure if you are actually pointing both eyes at the target. (I often think I'm pointing both eyes at a target, but really I'm only pointing one eye at a target.) I made a hand-held target, and targets for the wall.

 

You also need red/green glasses (of course) and a pen light.

Instructions for diplopia in front of the target
Look at the target (either in your hand or on the wall), and place the pen light between yourself and the target. Focus on the target, and try to make the pen light double around the target. If you do it correctly, there will be two pen lights, one red and one green, around the target.

You can make this activity more "task-y" if you place multiple targets on the wall, and make the pen light double around each of the targets.

Instructions for diplopia behind the target
Hold the pen light in one hand, and hold the hand-held target in the other hand. Place the hand-held target between yourself and the penlight. Focus on the target, and try to make the pen light double behind the target.

End of Instructions

Once you acquire the ability to notice and see physiological diplopia, you can use it to determine if you are pointing both eyes at the same place and not suppressing. For example: you are at school, listening to a lecture by your professor, and you want to practice pointing both eyes at your professor. Hold a pencil close to your eyes, and try to make the pencil appear on both sides of your professors face.

You can also practice this while reading, which I have seen called "bar reading" or "wire reading." Just hold something (a pencil, a wire, etc) between yourself and the book you are reading. Try to make the wire double and straddle the page or the words that you are reading.

My vision therapist told me about an exercise that she likes where the patient must hold a bendy straw in his or her mouth, with the bent part up.

In Guiding Strabismus Therapy, by Lora McGraw (It's a great book! You can find it here), I even saw a physiological diplopia device that could be attached to your glasses. It's called "The Beak", and allows a hands-free (but weird looking) physical diplopia check. I love it!

In conclusion, physiological diplopia is very fun and useful, and there are lots of ways to practice it. Try it out!

Vision therapy - weeks 10 and 11

Lately, I've been feeling like I have hit a plateau. I was getting used to the fast progress I made in the beginning of vision therapy, and I was hoping that every week I would continue to go into the VT office and say "Wow, Denise, guess what happened this week!" It hasn't been like that lately, though. It's more like, "Wow, Denise! I discovered a weakness that I need to work on!" Oh well. At least I'm learning something.

I've been doing some monocular work to improve my amblyopic, jerky left eye, like tracking a Marsden ball, putting pegs in a rotator board (and then putting ping pong balls on top of the pegs), and tracking the monster that the lives on the end of the pencil.

I've also been taking the polarized quoits vectogram home and desperately trying to see depth in it. Not much luck so far. I put a red square attached to a transparency behind the two sliding quoits to act as a fixed reference point in terms of depth, and I actually did see the square receding and the quoits approaching, and vice versa. Nothing ever left the page or jumped out, though. It was like watching the action happen inside of a fish tank, with nothing ever breaking though the glass. But I was still cautiously excited about that.

When I showed my vision therapist my trick, she wasn't so sure about it. Putting the red square behind the quoits messed up her vision so much that she really couldn't see anything, and said "If I don't see it, I'm not sure what you're seeing..." So I decided to give up playing around with those quoits for a while.

I was reading about monocular VT activities in Strabismus and Amblyopia, by Dr. Getz. Some activities involve tracking a crazy line all over a piece of paper, and some involve "o-filling", which is carefully filling in all the 'o's and closed loops (such as the loops in a, b, d, e, g, etc) in a block of text. As a graduate student, I often have hundreds of pages of academic articles to read every week. So I thought to myself, why don't I make that into a vision therapy activity? Isn't tracking text as good as tracking crazy lines or "o-filling"? This is what I came up with:

1. Sit centered and with good posture in front of whatever boring homework that you are reading. Make a conscious effort to keep your head straight. Do not do the strabby head tilt. If needed, wear a halo vest.

2. Patch the weak eye. Read with the good eye for 5 minutes.
3. Patch to the good eye. Read with the weak eye for 10 minutes.
4. Repeat steps 2 and 3 for as long as homework (or sanity) lasts.

Reading with my amblyopic eye is not easy. My eye is jumpy while moving from word to word and the letters look harsh and jittery and just plain weird. I also have trouble understanding what I have read, which I did not expect. Words are words, right? Why are they harder to process in one eye? I'm sure it's some brain thing. It always is.

I'm also curious as to why I have never seen this exercise in an vision therapy text. It seems like reading with your amblyopic eye would be an easy (in terms of materials) and useful exercise.

I'm guessing that the reason I haven't seen it before is either that it's not useful for some reason - it's too passive, or it doesn't have any motor feedback, or it has some sort of detrimental effect that I haven't predicted (intractable diplopia? a renewed hatred for reading?) or something like that.

OR

That it's left out because most vision therapy exercises are developed with children in mind, and no one considered the case of the poor graduate student who has to read all day.

A question for my vision therapist and optometrist readers out there: do you think that practicing reading with your amblyopic eye is a good VT exercise?

Abnormal retinal correspondence - new and improved!

In the past few days, I read some more books on strabismus and learned a lot more about ARC. I've also received some feedback on my explanations and diagrams. As a teacher, I'm not satisfied until I've explained something as clearly and accurately as I possibly can. And so, I would like present a new and improved post on ARC. Again, I'm not an optometrist, so I might not have everything right. But I think it's pretty close this time!

Correspondence - Normal and Anomalous

Like last time, let's start off with a look at normal correspondence (NRC).

NRC exists when the brain believes that both eyes point straight ahead, in the same direction, at the same place. The two foveas are "hooked-up."


Like I said earlier, this correspondence works great when both eyes are actually pointing at the same thing. But if one eye is deviated, visual confusion and double vision result. Why? Because the brain still has that deeply ingrained belief that the two foveas correspond, that they look to the same place. (I'm using exotropia as an example, but the same would apply to esotropia.)


In most cases, the brain suppresses one eye to remedy this problem. The fovea-to-fovea correspondence remains intact.


Here's where it gets complicated. Instead of (or in addition to) suppression, the brain can alter the correspondence. Let's say that your left eye deviates 45 degrees outward. Your brain operates under the newer, more realistic assumption that your right fovea points straight ahead, and your left fovea points 45 degrees to the left. That is an abnormal or anomalous correspondence.

In the case of exotropia, this can lead to a widened, panoramic visual field. Instead two eyes operating binocularly to make one image, the two eyes operate monocularly to make one panoramic image, neatly joined in the middle.


Again, I'm not sure if an esotrope would see a panoramic view. I want to say probably not, but you never know. The brain is capable of many strange adaptations.

So that's the first problem of ARC. The foveas are not hooked up, and true fusion is not possible. The fovea of one eye doesn't overlap with the fovea of the other eye. It's the like story of the sun and the moon, of Apollo chasing Artemis. The sun approaches the moon, and the moon moves farther away. They're always separated by that 45 degrees of abnormal correspondence.

The second problem with ARC is that sometimes fusion and stereopsis DO happen, but in an abnormal and degraded way. This usually happens with a smaller angle of strabismus.

Clear, beautiful stereopsis happens with a fovea-to-fovea correspondence, because the foveas are the areas with the sharpest, clearest vision. But sometimes, someone with ARC will designate a new part of their retina to be a *new* fovea. A faux-fovea, you could say. They will then fuse the true fovea of one eye with the faux-fovea of the other eye. This can happen with in both esotropes and exotropes, and I have illustrated it in an esotrope below.


The true foveas are the green spots. As you can see, this person is using the true fovea of his right eye in conjuction with a faux-fovea (orange spot) of his left eye to create a fused image. The true fovea of his left eye isn't being used. It's just shooting off into nowhere.

If this were someone with normal correspondence, they would have reacted with double vision, visual confusion, or suppression. But this person is able to use both eyes together via a faux-fovea.

So what's the problem? Aren't they still getting some fusion and stereopsis? Yes, they are, and that's exactly what some optometrists and ophthalmologists say. Leave those poor ARC patients with fusion alone! Their angle of strabismus is usually so small as to not be noticeable, and they have some degree of fusion. The problem is that the fusion gained through a faux-fovea is of lower quality, and true binocularity is hard to achieve because the eyes have developed a very hard to break habit. It's also hard for the patient in vision therapy to know if they are successfully fusing with both foveas, or backsliding into ARC.

To sum up, these are the two problems of ARC. Number 1, the foveas are not "hooked-up", and chase each other like the sun and the moon, never able to overlap. Number 2, sometimes a faux-fovea develops in the turned eye, leading to some sort of low quality stereopsis, and that habit is hard to break.

How is ARC diagnosed?

I've read lots of ways to test for it, and I don't pretend to understand all of them. For instance, some involve using "troposcope or major amblyoscope", and I have no idea what those are. However, in general, these are the things that point toward ARC:

-Evidence of "pasting" the images from each eye into a panorama, such as wearing red/green glasses and seeing a half red / half green room. Or as I like to think of it, the sun chasing the moon.

-Diplopia "against the rule". I don't fully understand this, but apparently when inducing diplopia in a patient, the esotrope should generally see uncrossed diplopia, and an extrotrope should see crossed diplopia. If an exotrope saw uncrossed diplopia, for instance, that would be "against the rule" and point toward ARC.

-Evidence of fusion in someone who is clearly strabismic and deviating. If someone with crooked eyes sits down in an optometrists chair and shows evidence of fusion while the eyes are still crooked, the optometrist considers ARC. Why? Because they must be using a faux-fovea. When the angle of strabismus is not very noticeable, the optometrist can do a cover/uncover test while the patient is fusing, which would show if they are fusing while being out of alignment.

-An ARC result on the Bielschowski Afterimage Test. This was the camera flash test that I mentioned in the previous post. You flash the fovea of each eye, one eye horizontally and one eye vertically. If they afterimages line up, it shows a fovea-to-fovea correspondence. If they don't, then this points toward ARC.

Should ARC be treated?

There are many differing opinions on if ARC should be treated at all. Here's what I have found:

-Don't try to fix it. It's dangerous to try and can cause permanent double vision. I've only read this in relation to ophthalmology, though. I've also read the same thing about treating suppression. Apparently everything is dangerous except cutting into your eye with a knife.

-Don't try to fix it, because it's too deeply ingrained and can't be fixed.

-Try to fix it, but if the patient looks good cosmetically and is a good faux-fuser, then maybe it's not worth the trouble.

-Try to fix it, but be aware that it can take a long time and is not always successful.

What is the treatment for ARC?

There are also many differing opinions on how to treat ARC. These are the methods I have come across:

-Start vision therapy with a STRONG emphasis on monocular training. Both eyes are trained separately, and the amblyopic / strabismic eye is exercised until it is equal in skill as the strong / fixating eye. This includes tracking, pursuits, and saccades. The exercises also include doing things like threading needles or stabbing Cheerios with a pencil, until YOU are able to do it equally well using either eye. This is supposed to orient each eye to the reality of the world, to make the eyes equal to each other (or close), and to show that both eyes correspond to the same reality. Visually directed movement activities can show the brain how the visual system lines up with reality.

-Bi-ocular tasks, such as anaglyphic (red/green) activities, that force fusion of the entire visual field. Touching and putting your hands on whatever you're looking at helps, too, and "proves" to your brain that each eye really does correspond in the same direction and to the same space.

-Dr Greenwald has a method of using prisms to cause diplopia in ARC. I gathered that the reason is to show the brain that the ARC adaptation isn't going to work anymore, and that a new correspondence must be developed (NRC).

My situation

With my current understand of ARC, this is what I can say about my situation:

-I have a tendency to "paste" and have a panoramic view of the world, but with some activities I can bring things together.

-Sometimes I have diplopia "against the rule", and sometimes I don't.

-I really don't think that I have a faux-fovea or any faux-fusion. I have to grit my teeth and straighten my eyes to do anagylphic / flat fusion activities, and I'm certainly not able to fuse while maintaining a deviated eye.

-When I do the afterimage test, I get an ARC response that I can bring into an NRC response by blinking and looking at a bright light.

So, what is going on with me? Why am I ARC sometimes, yet NRC at other times? Is it possible to be both? Apparently, it is possible. From Strabismus and Amblyopia, by Donald J. Getz, O.D. (it's a wonderful book, by the way!):

It is possible that correspondence will vary dependent on the conditions of the test. Often, some tests will indicate normal correspondence and other tests will indicate anomalous correspondence.

This above observation has led to the conclusion that what likely exists is a duality of correspondence. It is felt that what exists is an apparent anomalous correspondence with a latent normal correspondence. The most obvious example of this phenomenon is an intermittent exotrope who displays normal correspondence when the eyes are straight and anomalous correspondence when the eye is deviated. This is a relatively common observation.

Reading that certainly made me feel better. I just knew that there had to be a "both" option when it came to this correspondence stuff. I'm going to continue to work hard on my monocular and bi-ocular skills, until something magical happens, like recently happened with our friend Strabby.

I also hope that this post will be helpful for any other vision therapy patients who have read about ARC, and lay awake at night worrying about their correspondence status. Fear not!

Abnormal retinal correspondence

NOTE: I wrote this post when I didn't know very much about ARC. For a better post with better information about ARC, please read this updated post.

Abnormal retinal correspondence (or anomalous retinal correspondence) - ARC - is something that I worry about like a hypochondriac. I'm periodically convinced that I have it and that I'll never be able to achieve stereoscopic binocular vision. So, I thought it was time to write my worries down on the internet.

First of all, what the heck is it? Well... I'm not exactly sure. That's why it's so scary! It's a nebulous dark monster, waiting under my bed for it's chance to eat me. I've read a million things about it, and I feel like I get a different answer every time I read about it. But I will try to explain MY understanding of it, which could be completely wrong.

The first time I heard of ARC was in Fixing My Gaze, by Stereo Sue, quoted below:

**********

When we suppress input from one eye, we lose up to half of the visual information that's available to us. So, some people with strabismus unconsciously develop an additional strategy that allows them to make simultaneous use of both eyes, even though the eyes are looking at different regions of space. To do this, their brain abandons the idea that the two foveas point to the same location in space. Instead, they aim one eye at a target and interpret the location of images that fall on the central retina of that eye as straight ahead. (Assume here that the head is turned neither right nor left but is oriented straight forward.) Though aware of images that fall on the fovea of the strabismic, or turned, eye, they localize these images with reference to the "straight ahead" direction. If, for example, the strabismic eye is turned by 10 degrees, then images formed on the fovea of that eye are interpreted as being located 10 degrees from straight ahead. The fovea of the straight eye no longer corresponds with the fovea of the turned eye but instead with an area of the turned retina shifted by 10 degrees.

This is how my friend Bruce Alvarez sees... His response to the hole-in-the-hand experiment is different from what you probably observed if you tried it. He sees the hand in half of his visual field and the tube of paper in the other half. Bruce does not merge the input from the two eyes but instead reports what each eye sees separately. Although this is not the response that most people have, his view of the world, in this case, is actually the more accurate one. After all, the tube of paper is to one side of the free hand. Indeed, it is surprising to him that someone would have a different response. Bruce's unusual way of seeing is called anomalous retinal correspondence, an adaptation that often takes months or years of childhood strabismus to develop...

**********

The hole-in-the-hand experiment that she is talking about is this: Hold your hand up to one eye. Hold a cardboard tube up to the other eye. If you have normal vision, you will fuse the images and it will appear that your hand has a hole in it. If you are completely suppressing, you will just see a cardboard tube OR your hand. If, like Bruce, you have ARC, you will see reality: a hand next to a cardboard tube.

When I read that passage, I thought to myself, "When I do the hole-in-the hand experiment, I see what Bruce sees.... And I feel like I still see a lot out of my deviated eye... Hmm... interesting. I must have that ARC business."

Before I discuss myself further, though, let me try to explain my understanding of ARC. Again, I could be misinformed, but this is how I have come to understand it.

On the retina of each eye is an area called the fovea. It provides you with your clear, sharp central vision. In your brain, there is a LINK between these two foveas, and your brain operates under the assumption that the two foveas are ALWAYS pointing at the same place in space. In other words, the two foveas CORRESPOND to each other, and the brain fuses the image from each fovea into one stereoscopic image. Why does it fuse them together? Because, it is operating under the assumption that the two foveas always point to the same place in space.

This all works great when the two eyes are ACTUALLY pointing at the same thing, as in the image above. But what happens when one eye is strabismic and pointed at something else? Visual confusion or double vision results. Why? Because the brain still believes that the two eyes point at the same place in space. Thus, it fuses the images together into a crazy mess.

Going through life with double vision and visual confusion is not very easy, though. So the brain usually adapts by suppressing the image from one eye, trying to create some semblance of normal vision. The retinal link still remains intact.


There's a weirder, sneaker way that the brain can adapt, however. Break the retinal link! If the brain stops assuming that both eyes point at the same area of space, then the problem is solved. It adapts to the sad truth of reality: both eyes are NOT pointing at the same thing. Thus, each eye acts as an independent camera, with the images from both eyes being neatly pasted together in the middle.


This is ARC. The brain gives up on the notion that both eyes point at the same place in space. Instead of suppressing half of the visual field, it joins them together in the middle to create a panoramic view.

(I've read that ARC is much more common in esotropes, but I'm not sure how it works. Do they see a panorama? I'm not sure what they do...)

Anyway, back to myself. After reading that passage of Stereo Sue's book, I said "Okay, I have must have ARC. What an interesting factoid," and I didn't really think much of it. It wasn't until later, after researching it more, that I realized that it was not a good nor interesting thing. I read in Dr. Greenwald's book that Dr. Brock believed that ARC was incurable (though Dr. Greenwald himself did not believe this and had developed his own system for treating it). I also read that trying to convert ARC to NRC (normal retinal correspondence) can sometimes result in permanent double vision, and that some eye care professionals won't attempt it. And various other places, I just simply read that it was very hard to treat, with phrases like "exceedingly difficult" and "poor prognosis" being used.

At this point, I asked my optometrist and vision therapist if they thought I had ARC. Both of them didn't think that I did, and said that it was rare. My optometrist didn't think that I had it, but didn't really have the tools at the time to check if I had it or not.

So I said to myself, "I'll just figure it out myself." Here are my findings:

Josh's Findings
A report.

Hole in hand activity:
Result: Fail.

Camera flash test:

This classic ARC test involves flashing each eye with specially taped up camera flash.


-Hold it horizontally in front of one eye, stare at the piece of black tape in the middle. Flash.
-Hold it vertically in front of the other eye, stare at the piece of black tape in the middle. Flash.
-Close your eyes. Open your eyes. Look at a blank wall. Describe what you see.

When I do this test, I usually see one of the ARC versions. BUT, if I blink my eyes a lot, the two lines start moving toward each other into the NRC formation. What does that mean?!?! Fail? Pass?

Color Luster:
Wear red/green glass. Look at a light box. Try to mix the colors together. You fail if you see a half red light box, half green light box. My result: Mixed. I can see half red half green all day, but I can also make them mix a little if I squint and blink a lot.

Lid Glow:
Close one eye. Shine a penlight in your closed eye. Look at a black dot on the wall with your open eye. Try to make the black dot on the wall move into the glow you are receiving from your closed lid. Result: Pass... kind of. It's hard to do, but I can make it happen if I turn my head and blink a lot.

String test:
Wear red/green glasses. Hold a Brock string up to your nose. Fixate on a bead and make an X. If the GREEN string comes out of the RED eye, and the RED string comes out of the GREEN eye, you pass (crossed diplopia). Result: Passed with flying colors!

Bagolini Striated Lens test:
I won't go into detail about this test, but I got a weird result. I didn't get the ARC result, but I got uncrossed diplopia when I was supposed to have crossed diplopia (I think...). Result: Mystery.

Evidence for ARC:
I do a lot of things that one with ARC would do. When put on red/green glasses, relax my eyes, and look around the room, I see a half red half green room. I also feel that when doing fusion activities, I have to overcome the initial tendency to "paste" images from each eye together side by side. The first time I looked into the cheiroscope, I saw two totally separate images with no fusion. The same thing happened the first time I looked through a stereoscope, and the same thing happened when I first tried to do mirror overlap. Side by side images pasted together; panorama. I have also found it hard to gain even peripheral stereopsis, which is supposed to be "easy" (but this just changed today, see below).

Evidence against ARC:
I can also do a lot of things that one with ARC shouldn't be able to do. For example, I can make my eyes work as a team and play cards with antisuppression playing cards. I can see and play around with red/green tranaglyph slides. I can flat fuse a polarized vectogram into one image. I can do flat fusion stereoscope activities. And just today, I finally saw some depth on a polarized vectorgram! (but that's for another blog post).

Conclusion:
I believe have some ARC, but I am able to switch to NRC when doing vision therapy exercises that provide me with enough feedback (such as with anaglyphic activities and the Brock string).

I also believe that I have been self treating this ARC instinctively. When doing red/green anaglyphic activities, I often place objects that can only be seen by the RIGHT eye on the LEFT side, and objects seen by the LEFT eye on the RIGHT side. I then proceed to touch all over them with my hands to keep them "on." I have done this because it is "harder", and I now realize that it forces me to fuse the whole visual area into one image, and reinforces it with motor feedback.

If the object that can only be seen by the RIGHT eye is placed on the RIGHT, and the object that can only be seen by the LEFT eye is placed on the LEFT, then it is possible for me to "paste" the images together, even when wearing red/green glasses. Thus, the activity can be rendered useless by a smart brain if you're not careful.

I certainly hope that my tendency for pasting images together in ARC fashion isn't an insurmountable obstacle for gaining binocular stereoscopic vision. I work very hard to do my vision therapy homework and to force my eyes to work as a team. And I am usually successful. But I still have that lingering fear... What if it never happens? What if my brain is just broken?

Vision therapy - weeks 8 and 9

I keep labeling these entries weeks, but they are actually sessions. Occasionally, some sort of schedule conflict comes up and my vision therapist or I will have to cancel an appointment. But I still like to call them weeks. Sessions makes it sound like vision therapy only happens in the office. Like it's some sort of electroshock therapy or laser hair removal. That's not true. The real magic happens at home when you're doing your homework. That's when you discover lots of interesting and strange things about your visual system. You go to vision therapy and get instructions and get inspired, and then you go home and do the hard work.

Speaking of homework... After my week 7 appointment, I had a 2-3 week long break between vision therapy appointments. First I had the flu and couldn't go to my appointment one week, and then my optometrist and vision therapist went to a VT conference the next week. With all that time between appointments, I fell off the wagon in terms of homework. Graduate school and my ESL teaching job started up at the same time, and I just decided forget my eyeball homework altogether. I'll do it tomorrow, I thought. And then later I thought Well I haven't done it all week, so why start now?

When I did finally have my next appointment, I admitted to the vision therapist that I had been bad. I'm BAD, I told her. I have to get up at 6 am now and I don't know what to do with my life, and I don't know how to manage my time and I'm sorry I didn't do my homework every day. I'll start doing my homework again, I promise.

She believed me and didn't try to make me feel guilty, and I have been very good ever since.

Anyway, because it was week 8, I had an evaluation by the optometrist. He had me look through the phoropter, and put all sorts of weird prisms in front of my eyes. He said things like "Do you see one or two?", "Tell me when they are over top of each other", and "Tell me when they break apart into two." Or something like that. We did this for a while, and then he said that I had good control over my eyes, and a wide range of... something, and that I was doing very well.

My vision therapist has also been saying that she thinks I am "flat fusing." I can point my eyes at the same place, I can put on the red green glasses and see all the playing cards on the table, but I haven't had any sense of depth yet.

Divergence is still quite hard for me, too. Divergence is the opposite of crossing your eyes. It happens when your eyes look at something in the distance and the line of sight from each eye is almost parallel. Take a look at these illustrations I found of someone watching a 3d television.



(I don't know what "interocular distance parallax" means, so just ignore it.) In the first picture, they are converging their eyes on the TV screen. In the second picture, they have diverged their eyes to look "through" the TV, or at some point theoretically behind the TV. I can converge my eyes easily, and the closer the object is the better. I also am quite familiar with how convergence *feels*. But when I try to diverge my eyes like that, I don't know what I'm doing, I lose control, go strabismic, and start only using one eye. I don't know what divergence *feels* like yet.

I'm getting a little better at it, though. One thing that helps is to blink my eyes a thousand times a second. That helps break the suppression and helps my eyes relax and diverge a little.

Speaking of suppression, I still have a fair amount of that, too. I can see and fuse/not suppress big discrete things like playing cards on a table. But if it's something smaller, like little playing cards on a computer screen, laying over top of each other in a column, like in a game of Klondike solitaire... wow that's hard.

That's slowly getting better, too, I think. One of the exercises that I've been doing for the past two weeks is to wear red/green glasses and track this ball as it swings back and forth:


I made it myself. It's sort of a red/green Marsden ball. The first ball I made had a more random design, with lines and circles and squiggles all over it, but I found it hard to use. It was hard for me to "lock on ' to it.

I thought that using letters might be easier. My brain likes letters. If it sees letters, it's says to my visual system "Hey! Pay attention! What is that? Read that." It also allows me to say the letters out loud as I am tracking them, like some sort of incantation that will keep the letters "turned on."

"a b c... a b c... A B C!!" (Expelliarmus!)

I've also been playing around with a stereoscope. You can see a picture of one here.

You put special cards in it and look through the eye pieces. I can pretty much do all of the flat fusion exercises, like this turning these two soccer balls into one soccer ball with all the numbers:



When I look at the cards that are supposed to produce depth, nothing really happens. I fuse the images together into something flat.

The only exception is this slide of a chair.


When I look at it, it's not that I see depth exactly. It just looks weird and sort of *realer*, like I could be looking through a window. I had my normal-eyed friend look at it, and he said that the back of the chair looks really far away, which I still don't see. But something's certainly happening with that chair... It pokes at my brain in a funny way.

One last note - I've updated the comments system on this blog. I hope that it's easier to use now!

Do it yourself TBI

No, I don't mean traumatic brain injury. I mean Translid Binocular Interactor!

In my first few weeks of vision therapy, I went to the OEP online store and bought Effective Strabismus Therapy, by Dr. Israel Greenwald. I didn't really have a good reason, except that I had 30 dollars and wanted to know everything.

The book isn't an easy read, though. It's written for other optometrists, and seems to use the language of a scientific journal. It also talks about a bunch of VT instruments and gadgets that I either don't understand or know if have access to (Haidinger brush? polachrome orthopter?) Slowly, though, the more I read it, the more I understand. Going through vision therapy, getting experience with how my eyes work, and learning VT lingo is helping, too. I recently reread the chapter about monocular exercises, including exercises that help fix that jerky tracking on the strabismic eye. And I think I'm actually starting to understand WHY it's all jerky like that. Amazing! Maybe I'll write a blog post about that later...

Dr. Greenwald is still around and treating patients in New York City. If you read this, Dr. Greenwald, thank you for treating us strabbies and writing books about us!

Anyway. One of the things that I learned about in the book was a device called a Translid Binocular Interactor, or TBI. Now, as I understand it, a TBI is a device that puts rapidly blinking lights in your suppression zones. I'm guessing the theory is that if you put blinking lights in your suppression area, it will make it harder to suppress. You know, because of the blinking lights and all.

Some TBI devices are just boxes that you hold up to your eyelids, like this. But the TBI that I read about in Dr. Greenwald's book had the lights on movable clips. If you were an esotrope, you would clip them on the outer edges of your glasses, or even on the arms of your glasses. If you were an exotrope, you would clip them on your glasses toward your nose. Basically, you're placing them in your area of suppression.

I thought this TBI gadget sounded useful and I immediately had to have it. But my vision therapist / optometrist didn't own one, and they cost over 250 dollars for the kind that clip onto your glasses. 250 dollars for TWO blinking lights?! Are you kidding me? Surely, I could come up with some kind of cheaper substitute...

I'm not an electronics person, though and I don't really get how all that stuff works. Volts and amps and ohms... I just don't understand. But surely, making a light turn on and off is not something that requires a graduate degree in electrical engineering to figure out.

Then I remembered. LED throwies. LED throwies are a a coin battery, an LED, and a magnet, all taped together with electrical tape. The LED lights up, you throw them (hence throwies), and the magnet makes them stick to whatever (metal) structure you threw them at. They're kind of like electronic graffiti.

The LED lights up just by making contact with the coin battery. No wires, no complicated electronics. I thought to myself - What if I use a blinking LED instead of a regular LED, and use an alligator clip instead of a magnet?

So I went to RadioShack, gathered my supplies, and made my own homemade TBI!



The only blinking LED that I found was red, and certainly did not blink 7-10 times a second. I didn't really mind, though. It's a close enough approximation for my purposes, and doesn't cost 250 dollars.

Here are the instructions for making your own:

Materials:
- 2 coin batteries
- 2 5mm blinking red LEDs from RadioShack
- 2 alligator clips (Note: the clips shown in the picture are too small to tape the coin battery to. Use bigger clips.)
- stiff paper (I used a manila folder)
- electrical tape
- scissors


Step 1:
Cut out a strip of stiff paper that will wrap around the coin battery.


Step 2:
Tape the paper to the battery using electrical tape. You now have a little pocket on each side of the battery in which to insert the "legs" of the LED.


Step 3:
Curl the "legs" of the LEDs, like the one on the left. This will allow the LEDs to fit into the "pockets" on the batteries.


Step 4:
Put electrical tape around the "teeth" of the alligator clips. This will protect your glasses from teeth marks. (Note: Again, the clips pictured are too small. Use bigger ones!)


Step 5:
Tape the coin battery to the alligator clip. (The clips pictured are now the right size.)


Step 6:
Insert the LED into the pocket. It will start blinking. Clip to your glasses and have fun. (Note: the LED will only light up if each "leg" is on the correct side of the battery. The short leg goes on the smaller side of the battery, and the long leg goes on the bigger side of the battery. If you put the legs on the wrong sides of the battery, the LED simply won't light up. Switch the legs around and try again.)


I've played around with these, and I've found it best to position them so that you don't actually have the LED directly in your field of vision. Position them so that you get indirect flashes of light. I think it's called Translid for a reason. While wearing them, do whatever vision therapy exercise that you wish. I've used them while using the Brock string, to help me see all four strings.

When you're finished with your exercises, pull the LEDs out of the pockets. This will turn your device off and save your batteries.

WARNING: I am not a doctor or eye care professional of any kind. I don't know if it's safe to put RadioShack LEDs up to your eyeballs. Do so at your own risk. Also, those with epilepsy should not use flashing lights near their eyes, either.