P3D use of 'cyclopean'

[Peter Abrahams <telscope@xxxxxxxxxx>]

We've had some discussion on whether referring to binocular vision as
'cyclopean' is misleading, and there are certainly points to be made there.
 But I think that for this email list, or individuals who participate in
it, to declare this association to be invalid or nonsensical, is a futile
exercise and also misses a certain logic.
First: the use of cyclopean in this sense is very well established in
vision literature.  It is not the only term used, but it is widely used.
Second: there is a limited logic here.  When you perceive two images (cross
eyed, for example), you are not using binocular vision.  When you perceive
one image with two eyes, you are using binocular vision.  It's like the
inaccurate movies that show a view through a binocular as through two
tubes; when in fact when you use a binocular, you see one image.  Certainly
the single image from two eyes contains depth information that is not
present in a monocular view.

I agree it is confusing, and might better have been avoided.  When I refer
to binocular vision, I don't use the word.  But no one asks my opinion on
the issue; and the people whose opinion I'd value often use the word.
Unfortunately, the connotation to me involves what Ulysses did to the poor
big dummy.

Binocular vision is a hugely complex phenomenon, and I think it likely that
'cyclopean' can contain some precision of meaning to knowledgeable readers.
 For example, is it properly used to refer to a mental image, and not a
function of the eye?  Is it properly used to refer to a single image
without depth information?  It at least seems to be used to refer to neural
processes.

I cannot give an authoritative answer to the exact meaning of the term, but
I can cite a couple of usages from Howard & Rogers, Binocular Vision and
Stereopsis.
p151, "shapes visible only after monocular images are combined are
cyclopean images." (example, random dot stereograms).  p591, "what location
in the head serves as the origin....... such directional judgements.....are
referred to a point midway between the eyes....the cyclopean eye".  p587,
some effects of binocular vision can arise when the two stimuli are
combined in the same eye.  p585, a cube can be visualized when half the
lines are shown to one eye & half to the other.  p589, motion in depth is
complex & involves more than simple fusion, for example there are motion
aftereffects after prolonged viewing.  
You might reply, all this goes far beyond stereo vision; and this is true
but these effects are an important part of our stereo vision.

p6, Galen (129-201 AD) "believed that the meeting of the optic nerves in
the chiasma united impressions from the two eyes into a single
experience......this idea gave rise to the notion of a cyclopean eye
located at the chiasma......idea not overthrown until the seventeenth
century.  We now talk about the cyclopean eye to refer to the fact that we
judge the directions of objects as if we see from a single eye midway
between the eyes."  Helmholz used the term this way (not sure what the
German word was).
p3, "The term 'cyclopean' is difficult to define because different authors
have used it in different ways.....the term is used to describe a birth
defect in which there is only one central eye {this might be a problem here
at p3d, maybe we should open argument by declaring our arsenal of
eyes}.......Julesz, the term seems to have the same connotation as 'central
processing' as opposed to 'retinal processing'......We use the term...to
refer to a stimulus formed centrally but not on either retina -- it can be
said to bypass the retinas....beyond the primary visual cortex......infer
that a process is cortical"

_______________________________________
Peter Abrahams   telscope@xxxxxxxxxx
http://www.europa.com/~telscope/binotele.htm