Re: dangers etc

[P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>Date: Fri, 27 Sep 1996 22:12:41 -0500
>From: P3D Wolfie!  <werewolf@xxxxxxxxxxxxxxxxxxxxx>
>Subject: dangers etc

>The thing that I discovered about the eyes behaviour is that they become
>"used" to seeing a certain thing and it takes a while for them to settle
>back.

>for instance, we all know that after coming off a ship or a even a train 
>after a very long ride will leave our legs feeling really weird when we
>finally get back onto land.

>the eyes are no different, I have played videogames in the past where my
>eyes would still be moving in the same way as the main sprite long after
>I had switched off the machine and was laying back reading a book...
>which in this condition wasn't that easy. :)

>Unless the freeview images are set too widely apart and you strain to
>"join them together" [which you shouldn't ever do] then I really cannot
>see how looking at them or through binoculars or microscopes can do you
>any harm at all.

>Take Care!

This has been discussed several times in the past on photo-3d, and I once
gave a reference to a paper that was presented at SID '95. The concern seems
to be oriented more toward head-mounted displays and VR systems than toward
static viewers, perhaps because the former can be considered one step closer
toward "reality". Given the extreme level of caution that's shown up in the
VR business, I would guess that at least some of the people involved are
concerned that there could be something to it. The VirtualBoy never made its
initial release date, and when it did come out it included dire warnings about
what could happen if you don't adjust it correctly for your own eyes. Some
people in the graphics industry have recently indicated that there may be a
shift from head-mounted VR systems to fixed displays, at least with the
current level of technology.

As I understood the SID '95 paper, there were two main concerns:
 1) A short-term disorientation, lasting up to several hours. This was
    measured in test subjects, and a significant percentage had noticeably
    reduced accuracy of depth perception following use of a VR system. The
    amount of degradation varied widely by the type of system used. (This is
    part of what "Wolfie" described). It was recommended that people avoid
    activities such as driving for a while after using these devices.
 2) Possible long-term effects. This could be accounted for by the brain's
    ability to logically "rewire" itself, including the visual centers.
    The addition of new connections takes place fairly easily, while old
    connections that are no longer needed tend to persist, and there may
    not be any particular mechanism to remove them (e.g. the old saying that
    you never really forget how to ride a bicycle). When a new activity is
    learned, the new pathways are added to the collection of existing
    pathways, and if both old and new pathways are stimulated at the same
    time, confusion can result.

I don't know to what extent the long-term effects have been shown to affect
stereo vision after use of poorly-designed VR or static 3D viewers, but the
general phenomenon has been described in other fields - people who have had
a limb amputated may suffer "phantom pains", and people who have lost a sense
may observe a strange mixing with other senses (e.g. a blind person experiencing
visual phenomena when certain sounds are heard). A theory is that parts of the
brain, deprived of their ordinary input, may actively encourage rerouting to
find other sources of stimulus. If a viewing system provides anything other
than an exact duplication of reality (which describes all current viewing
systems), then it will generate a perceptual environment in which the
creation of new "pathways" in the brain is encouraged.

Note that some of these phenomena may be hard to measure. A change in the
perceived relationship between focus and convergence may be offset by a
heightened ability to use convergence alone. It may also be possible to train
the brain to select the perceptual pathways to be used based on the context
of the situation - in that case the confusion of multiple signal paths could
be avoided.

The point of the above comments is not to say that 3D is definitely dangerous,
but to point out that there *are* known mechanisms in the brain by which
some forms of stereo viewing *could conceivably* cause problems, so a degree
of caution would be advisable until researchers have had a chance to figure
things out.

A working "rule of thumb" for non-conventional viewing methods that is often
recommended is to "take it easy" - don't strain, take frequent rest breaks,
and if there seems to be a problem, desist until you're sure everything's OK.

John R.


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