P3D Re: Dark Vergence (was: Curious eye defect)

[Linda Nygren <lnygren@xxxxxxx>]

Andrew Woods wrote:

> I have a half baked theory that an individual's value of dark vergence
> (also known as Heterophoria) has some effect on whether they are more easily
> able to view stereo-pairs in the cross-eyed or parallel formats.
> I suspect if a person has esophoria (the tendancy of the eyes to turn in
> when the stimulus of fusion is removed) then they will find it easier to
> cross-view.
> Similarly if a person has exophoria (the tendancy of the eyes to turn out
> when the stimulus of fusion is removed) then they will find it easier to
> parallel-view.
> Like I said, still a theory...  I'd like to do some more research in this area.
> 
> Andrew Woods             http://info.curtin.edu.au/~iwoodsa
This is certainly true in my personal experience. I have "exophoria"
meaning my eyes tend to wander "out" if one of my eyes is blocked, for
example if I am sitting behind someone at a theatre and I can only see
with one eye, the other eye loses its "fixation". It feels weird.
Anyway, I find that I can easily parallel view but I can't cross view at
all because my eyes just won't do it! Doctors check for "phorias" by
doing a cover/uncover test where one eye is covered while the other
looks straight ahead; then when the eye is uncovered, it may be seen
moving back into a normal fixation position from where it wandered in
(esophoria) or out (exophoria). You can check yourself with the help of
an observer if you are not sure whether your eyes tend to do this.
-Linda


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