Wednesday, February 3, 2010

Reflections on Stereo Sue's Book: Fixing My Gaze -- Part 1

Allegory of the Five SensesImage via Wikipedia
Dr. Sue Barry, "Stereo Sue", is a neuroscientist who has had serious problems with her vision including a lack of 3D vision and documented her struggles to gain normal vision in her book,  "Fixing My Gaze".
One of the things Sue Barry mentions when trying to get stereovision true vision therapy, it requires not only proper lenses or prisms but very intensive training. You must learn how to align the eyes and fuse the images while unlearning the unconscious habit of suppressing vision.

I have a similar problem I am not using the images provided by my two eyes. I see the input from one eye at a time and switch rapidly between the two eyes.

I also have a problem with converging my eyes properly that is, turning in my eyes to see something close to me. And then diverging that is, turning my eyes out, to see things further away.

The difference in viewing perspective between our two eyes provides us with stereopsis, or depth perception.

Some things that are interesting is that a 3-D movie filming the scenes with two cameras taking pictures from slightly different perspectives. When you put on 3-D glasses, each eye sees the pictures shot by only one of the cameras. Your brain does the rest of the work, fusing the two images into one scene scene in depth. I think I still have some depth perception because I can enjoy 3-D movies and I have created 3-D virtual reality and have used crystal lenses successfully to see 3-D. There are some people who cannot see the current movie, Avatar, in 3-D.

Berry also talks about her husband's sense of flight and vision. As an astronaut, life in freefall means his sense of up-and-down is distorted. When he closed his eyes in space, he had no sense of up or down. This reminds me of some of the distorted sense that I had during my balance test or during Balametrics when I was trying to walk on the balance beam with my eyes closed. Things are much harder when you can't rely on your vision to stabilize yourself. This sense of up-and-down is regulated by your inner ear and the vestibular system. The brain does more sensor fusion than just pairing the two eyes. It also combines all the input coming from all your sensory organs (eyes, ears, nose, balance, etc.) into a unified view of the world.

Poor ability to fuse images from two eyes makes it hard to know exactly where objects are located in space. I think this has a lot to do with why I can be very clumsy and not pour water from a pitcher into a glass without spilling it. Or, how I tend to want grab a hammer at its head instead of at its handle. I am a bit afraid of whacking my thumb and not the nail.

So how do I function? Since I don't have depth perception that is supplied by binocular vision, I rely on  "monocular cues" to depth, such as shading and perspective. I look at the differences in shapes and I use motion parallax when I drive. I have a greatly impaired sense of distance and space. This can affect my posture because I tend to lean in to see things. As a friend of mine who is a physical therapist puts it, I use the praying mantis position at a desk with a computer.

None of these problems ever got caught during eye exams given at school or with an ophthalmologist. The Snellen eye chart -- the chart with the big letter E. on top measures visual acuity. We need more than 2020 vision to read.

I am also slow at copying information. I have to look back and forth from the source to my pen or computer multiple times compared to other people. It's not that I'm not paying attention. I just don't see things properly or remember them as other people do.

I have convergence insufficiency I don't align my eyes properly. I don't converge my eyes for near viewing. This is really hard when you are trying to do work close up. For example, sewing. Like the author, I really hated to sew. Home economics was a huge chore.  I had a most unsympathetic teacher who would just stare at me as I struggled with the sewing machine making me a lot more nervous than what I really needed to be.  Cutting the fabric to measure was very hard and sewing was worse.  It would take me almost the  whole period to thread the machine.  Trying to synch my poor eyesight with lousy motor skills made operating the machine a bit of a race between the fabric, the needles and my fingers.  It was exhausting.

  My mother called my home economics teacher  "sharp" but not in a kind way... She was a sharp dresser and read Cosmopolitan magazine while she wasn't monitoring the class.  I never finished my dress in time for the class and I received a  "D" in home ec.  Fortunately, my next-door neighbor was good at sewing and she took me under her wing and I did finish the dress.  There was a big difference in the orderly way that my next-door neighbor could put together the dress and the very haphazard way I approached the whole project.  Somehow I noticed that other people were more orderly and I was a bit of a klutz and a mess at doing very simple things.  This did not bother my parents.  Even in the 60's before women's lib really hit, they were programming me into being a professional career woman and not a housewife.  Just somehow, the every day chores would get done... somehow.

But, really, the day-to-day was not very important to my parents.  The life of the mind was.  It was more important to go to a cultural event such as a museum visit than it was to clean the house.  I think my parents' were handicapped as well... and to compensate, they dwellled in the world of the mind.