Re: speculations regarding vision

[Barb_MSN <Barb_MSN@xxxxxxxxxxxxx>]

Tom....

I have no gait problems, tho I DID freeze prior to my Oct. 1994
pallidotomy.

I had no noticeable vision problems at that time, and the vision
problems I'm currently having began about 3 years ago.

Keep up your unique research as I think you're on to something.

Barb Mallut
barb_msn@xxxxxxxxxxxxx

-----Original Message-----
From: Tom Riess <74244.1521@xxxxxxxxxxxxxx>
To: PARKINSN@xxxxxxxxxxxxxxxxxxxx <PARKINSN@xxxxxxxxxxxxxxxxxxxx>
Date: Tuesday, May 04, 1999 8:09 PM
Subject: speculations regarding vision


I too have been most impressed with the number of PWP who report
problems
with vision.  It prompted me to ask the following question which
went
largely unaswered:  of those of you who have problems of vision,
how many
of you also have gait disturbances?  According to my unproven
speculations
I would propose that there are two categories of vision:  one is
conscious
seeing which is seeing in the "ordinary" sense i.e. vision
filtered
through the eye of experience.  This is the kind of vision which
enables us
to identify a familiar face or object.  But I would  propose there
is  a
second category of vision which I call unconscious vision.  This
vision
(primarily peripheral) is used to monitor motion, generally
apparent motion
i.e. it monitors motion which only seems to occur and is the
result of our
eyes moving from one vantage point to another.  This unconscious
vision
only becomes conscious when it is not in compliance with the motor
activity
which produced it.  When this is the case an "explanation" is
required to
resolve this conflict. In the absence of an adequate explanation
motor
activity stops (e.g. freezing).   Here is a more specific example.
Imagine
yourself driving your car and you are  stopped  at an
intersection.
Suddenly the parked car to your right begins to bac   kup.Sensory
conditioning has taught us that peripheral motion is usually
apparent not
real and  signifies movement of ourselves.  This apparent conflict
causes
us to reflexively slam on the brakes (freeze).

The point of  all this is that all the PWP who reported vision
problems
naturally  reported problems of conscious vision (e.g. depth
perception
changes, double vision).  However, I would suggest that problems
of vision
very likely crossover into the realm of unconscious vision.  Since
unconscious vision is a reflection of motor activity and can
determine
whether or not such activities are performed as well as the
characteristics
of  their performance, this raises the possibility that visual
perceptive
or processing pathology could be a cause of gait disturbances in
PD.

Regards,
Tom