Do you control your eye alternation? An additional diffilculty.

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Permalink Reply by Cynthia Freeland on May 14, 2012 at 9:56pm

I am like Frances who replied below, that I can control it and be aware of it but usually my brain runs the switching on "automatic pilot." I am a rapid alternator but usually I use my right eye for closer work such as reading, viewing the computer screen, etc., and my left eye for distance viewing such as when I go to the opera. I can make the switch but usually they just switch without my thinking about it. I have no double vision or fused vision at all. I saw Dennis Levi when he was at our Optometry School here in Houston (he's now Dean of Optometry at Berkeley) and he thought at the time--now keep in mind this was more than 10 years ago--that the kind of vision therapy they did then would not help me because I was at the 99% end of the spectrum (I'm not quite sure WHICH spectrum, either strabismus or rapid alternators?). I felt the various side effects he described and amount of effort involved would not be worth it.  I don't pass any of the 3D vision tests but to me the world just doesn't look flat.  So I'm rather puzzled about the whole thing.

Permalink Reply by Frances McIntosh on May 17, 2012 at 7:40am

Hi Cynthia,  It can be so hard to describe certain aspects of vision.  Sometimes one doesn't know what one hasn't got because they've never had it.  Have you read Susan Barry's book?  

I'd know for a long time that I lacked B.V.  And I'd spent many hours on and off talking with my Mom on the subject, each of us trying to understand the difference.  So I had *some* idea about it, but didn't think things really looked "flat." 

I don't think Barry did either.

In an interview on NPR  (I think) she mentioned meeting Oliver Sacks and having a conversation with him on the subject of depth perception  As a biologist who taught neurobiology at  Mt. Holyoke she was confident that she knew what depth perception was about.  After her vision training she got in touch with him and said  (in effect) "I had no clue!"  

If you've read her book then your puzzlement puzzles me.  Perhaps you've got some of the visual skills that I'm hoping to acquire with vision training.  Depth perception is out of the question for me but it is probable that V.T. will teach me to use my eyes in ways that will make it easier for me to function.

Let me know if you've read Barry's book.  If not I highly recommend it.  You might be in for a surprise!

-Frances

P.S  I was a subject at the Levi Lab in Berkeley.  Long story short: The research was not on B.V. but it was really interesting anyway.

P.P.S. You may want to get checked our again re: V.T.  A lot has happened in 10 years. And even if you're told that B.V is out of the question an/or if you are told that V.T. can't help you in *any* way talk to folks here.  

I don't know yet about what improvements might be possible for me, but I should have a better idea in a few weeks.  I expect to be posting about that here.

Permalink Reply by Pablo Manzano on May 17, 2012 at 8:12am

Why is it out of the question for you? If you learn to point your eyes, to use both at the same time or even to alternate very rapidly, your brain will learn by experience what the difference in point of view between the eyes means. Perhaps you wouldn't get a very precise depth perception, but even if it was a very vague one, it would be something. And if you get to that point, you can surely improve upon it.

Is your case so definetely closed?

Permalink Reply by Frances McIntosh on May 17, 2012 at 10:48am

As I understand it it goes like this:  Testing has revealed (I don't understand how, but it's been done several times. Two times by optometrists--well three if you count both the optometrist at the U.C. B.V. clinic *and* the director of the department--and once by an opthamologist) that in my brain the cells responsible for creating the magic of depth perception are not available.  

They're either gone or so atrophied that they can't be revived.  Since I probably never had depth perception (or had it only very, very briefly a long time ago) it's probably a case of "you-don't-use-em-you-lose-em." 

Since they are not usable, no amount of rewiring to "get to" them is going to help.  And since these cells are so highly specialized, you can't get other cells to step in and do the job. 

All of which means that brain-plasticity doesn't help.

And there are other possible factors, which I understand even less.  (Check out SquintyJosh's blog on the subject of ARC.):  

http://squintyjosh.blogspot.com/2011/02/abnormal-retinal-correspond...

Permalink Reply by Pablo Manzano on May 17, 2012 at 11:17am

"you can't get other cells to step in and do the job. "

I am not a neurologist, but I would say this doesn't sound true to me. As far as I've read one of the most important discoveries about the brain is that its areas are initially assigned to especific tasks only if they are available. If one of them is not working, other areas of the brain can develop the same functions (probably with much more effort). For instance, Kirk Douglas lost the hability to speak because of neurological damage. The part of his brain used for allowing him to speak became dead. But, with effort and time, he was able to speak again. He must be using a different set of neurons now when he talks, because the original ones are dead! He speaks in a different way than he used to, more slowly, perhaps less skillfully, but well enough anyway.

And about depth, I have started to see some, and I would say it is something you learn as you start to use your eyes as a team more and more. I'm not sure about this, but my optometrist told me that the skill is partly learned by experience.

People who told you you cannot see depth must surely know more than we do, but if I were you, I would do as much research as possible on these subjects.

Permalink Reply by Frances McIntosh on May 17, 2012 at 4:35pm

Many survivors of stroke and other kinds of brain injury can get other brain cells, even from other parts of the brain to take over for the damaged or destroyed ones.  But it is my understanding is that the cells involved in creating depth perception (which I think are called "disparity sensitive cells") are just too highly specialized for that to be possible.

Your optometrist is right of course about depth perception being in part something you learn.  But I think it's that "in part" bit that is the problem.  The other part may be the hardware (those specialized cells).

You can't learn to drive a motor vehicle if you don't have one.  You can learn to ride a bicycle.  But it's not the same.

I'd love to have a car. But given that I don't, a bike is better than nothing.

I'd love to have fusion/B.V.  But given the fact that I don't, 2-V vision is better than nothing.

I have to admit that since I read Sue's book it's gotten harder to see everyone else either zipping around in cars or in the process of a getting them.  But then there's my three blind friends.  Perhaps the analogy would be that they have to walk everywhere.

And I'm an artist; I find that seeing what I do see already gives me great pleasure.  And (if you can stand another analogy):  It may be as if I can only see in B&W.  But there is still a lot of beauty to be seen.  Have look at some of the wonderful B&W photography out there.  (In some cases color would even detract from their beauty!)

Anyway, enough analogizing and philosophizing, and back to facts (as we know them).

Both the researcher I worked for (as a research subject) at the Levi Lab and the first optometrist I consulted told me the same thing about specialization. "You can't learn to use what you ain't got."  (Or words to that effect.)   And the optometrist who's supervising my V.T. now has agreed about my prognosis--though  I haven't spoken with her about the specialization issue. If I get the chance I will.  

Perhaps if you get the chance you might ask your optometrist as well.

-F

Permalink Reply by Pablo Manzano on May 17, 2012 at 6:34pm

Sure. I'll do that when I see her in a few days :)

Permalink Reply by Frances McIntosh on May 17, 2012 at 11:44pm

Cool.  You'll probably be first.  I just saw my V.T.  It'll be interesting to find out what they say. -F

Permalink Reply by Pablo Manzano on May 30, 2012 at 6:55pm

I finally spoke with my optometrist about your case as you described it here. She says that, on one hand, it is very hard to assume that one person could NEVER gain ANY stereo vision AT ALL without having tried it during some amount of time and with different techniques.

There is no way to tell that your disparity sensitive cells are ALL dead, except by experience. For instance, I never used both eyes at the same time either, so they could have thought that my binocular neurons were dead as well. In fact, they didn't expect me to gain depth perception: they simply started giving me therapy to do to see where the results led us. Eureka!

On the other hand, my optometrist says, there are cases in which the immediate results of therapy for gaining binocular vision are so uncomfortable and life-changing for worse (things like double vision, headaches, loosing a stable vision of the world), that she wouldn't recommend even trying to see if it works. She thinks that yours seems one of those cases: your vision works in such a different way from the stereo one that perhaps changing it would require having vision problems during a long time without being sure of a positive final outcome (and certainly, a lot of work). She has read about patients with a vision very much like yours who encontered a lot of trouble out of this type of therapy.

However, I guess you could always try it. It's only that you need to know that it might be risky.

Permalink Reply by Frances McIntosh on May 31, 2012 at 3:46pm

Hi Again,  

Pablo, thank you for taking the time to talk to your optometrist, to take the time to organize the information so well, and to post it here.  I want to respond at greater length but will stick to the double vision issue for now:

When I was considering surgery to align my eyes the question of double vision came up.  However after a some testing the optometrist and the opthamologist agreed that even if that happened my ability to choose which eye I'm "using" is strong enough that I would overcome the problem within as little as one or two days.  

I think the idea is that although I don't suppress the image from one eye I can (or can easily learn to) *ignore* the image from the eye I'm not choosing to "use" at any given moment.

-F

PPS:  In a sense I already have both "double vision" and "binocular vision."  I'm always seeing two images. They just don't overlap!    :-)

Permalink Reply by Frances McIntosh on June 2, 2012 at 8:57pm

Hi Pablo,  Thanks again for detailed well organized response!

I was not able to go to V.T. this week.  (I have a chronic, debilitating illness that fluctuates unpredictably.)  So I only had a brief conversations with her on the phone about homework when sick.

But, thinking back on previous conversations I think that there has been and will continue to be some of the "try this and see what happens" approach. And that there may already have been a bit of a change in my prognosis.  (I've only had the evaluation and 3 actual therapy visits.) 

It's still clear that stereopsis is not the goal of V.T. for me. But it seems that it may be possible to provide me with a kind of vague, faux depth perception using some of the cells in my retina that are normally used for peripheral vision.

I had thought that depth perception was an all or nothing thing.  One minute you're seeing in 2-D and the next the steering wheel is popping out at you.

But this business of using retinal cells normally used for peripheral vision brings up a couple of questions for me.  I haven't been able to ask my therapist about these but I figured I'd ask them here and see if anyone has any ideas:

Wouldn't using peripheral retina cells to create depth perception require functional disparity sensitive cells?  And if so, then why not use the foveae rather than peripheral retina cells (and get clear stereopsis?

As for the risks.  My optometrist and my therapist haven't said anything about risks.  I'd expected some eye strain (which I do get) but thought that it would either work or it wouldn't.  So I will ask about risks next time I'm in.

My questions seem to be breeding!  The more answers I get the more questions I have.  (Which is a good thing actually.  LIfe without questions would be so dull!)

-F

Permalink Reply by Cynthia Freeland on May 31, 2012 at 12:11am

Hello, I'm trying to respond both to you and Pablo. Since I saw these posts I have consulted another optometry professor at my school, University of Houston, and she reported something similar to what Pablo reports his optometrist said. In my case, she said, she could train me to stop suppressing the visual input from one eye, which I am now doing, but once the suppression is overcome, you can't get it back. There is no guarantee of fusion and a lot of likelihood of double vision, and she really did not think I was a good candidate for their vision therapy program.  I am too scared of having that happen to want to risk it.

Cynthia

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