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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 [log in to unmask] -----Original Message----- From: Tom Riess <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> 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 back up. 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