Bobby you are just too smart.  Figured if I waited to see if anyone answered
first.  Now for the OT side of it.  Bobby's right there are five skeletal
muscles that move the eye, side to side up and down, around etc.  They are
also highly innervated by cranial nerves (direct input into the brain)  One
of the main things I look at for the kids I evaluate is simply vision test.
Not the kind the eye doctor gives you, but can you track accross midline and
do your eyes converge (come together) and diverge (go apart) smoothly.
These functions are controlled by those skeletal muscles connected to your
eye ball.  Depth perception is the result of your two eyes working together
near pt. convergence and far point.  Each eye sees a different picture and
when put together in the brain gives you a stereoscoptic (sp?) view of the
world (think 3-D glasses or those Victorian stereoscopes with two pictures,
or view finders) If along the way your eyes aren't lining up properly the
brain takes over and often times cuts out information from one of the eyes,
thus no binocular vision, no stereoscoptic view, etc.  That's one way.
So think about how folks with CP and other neurological disorders have
difficulty voluntarily controlling muscle movements and how depth perception
is a quick change muscle movement as your eyes adapt to a changing
environment and it will make sense.
That's my 2 cent lecture on vision.  It's very fascinating stuff.

Beth the OT

-----Original Message-----
From: St. John's University Cerebral Palsy List
[mailto:[log in to unmask]]On Behalf Of Bobby G. Greer, Ph.
D.
Sent: Wednesday, November 28, 2001 7:56 PM
To: [log in to unmask]
Subject: Re: balance and growing up with CP


>Can someone please explain how CP affects depth perception?  I am curious
>about how the two
>relate.
>Thanks,
>
>Jeremy

Jeremy,

    My best guess is that CP in some persons affect the six extrinsic eye
muscles which move the eye. The kinesthetic difference between these sets of
muscles is one of the primary sources of depth perception. This is my
speculation from a course on vision testing I took longer ago than I care to
say. LOL More recent knowledge may offer a more accurate explanation.

Bobby