Dangers of freeviewing (repost)

[P3D Dr. George A. Themelis <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Repost from Digest 885 regarding the health dangers of free-
viewing:
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John Roberts' posting reminded me of something that I read in 
the book "Manual of Photographic Interpretation", published by 
the American Society of Photogrammetry in 1960.  
 
In chapter 3, "Fundamentals of Photo Inerpretation", the author 
Ellis L. Rabben writes the following about freeviewing:
 
   "Naked-eye stereoscopic vision is an interesting and 
   often convenient stunt.  If adopted as a habitual 
   practice, however, it can cause accommodation and 
   convergence to assume a new and anomalous 
   relationship.  The interpreter may then see double, 
   or his vision may blur, at odd times, because the 
   stabilizing relationship between accommodation and 
   convergence has been disrupted."
 
I wonder if there is any scientific truth to this statement.  If 
not, as I suspect, then how come it found its way in what appears 
a reliable & scientific reference? 
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George Themelis, freeviewing with no side-effects (yet!)


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