P3D Re: VM and kids - etc.

[Bob Wier <wier@xxxxxxxxxxxxxxxxx>]

A>The best way to use a stereoscope is to have the pictures in the
>focal plane, so that parallel rays come out of the lenses and you
>can look without accommodation. For normal sighted people this 
>means that focusing should be done by moving the lenses as close
>as possible to the pictures (keeping them sharp of course). 
>Then you look at far points without accommodation and parallel 
>eyes axes. 
>
>When this would be done by everyone the theory would work, but
>unfortunately people KNOW that the views are very nearby. 
>Many of them therefore unconsciously converge (squint) and 
>accommodate when looking in viewers. They of course try to adjust 
>focus and eventually interocular, sometimes getting fusion and 
>sometimes not, several with eye strain and probably divergence.
>This seems the mean reason why some people, with otherwise normal
>stereoscopic vision, fail in using some viewers.
>Try to convince them that the stereo scene is deeeeeeep.
>
>Abram Klooswyk
>
>
This is interesting. As I've posted before a couple of times, several years
ago I had a pair of eyeglasses cut to be used as a stereoscope. I took a 
card with me to the opthamologist (since I had an appointment anyway) and
after doing everything else (except dialation) we experimented around a bit
to see (slight pun) what we could come up with. In order to get a usable
image size, I found that for a standard Holmes type card a viewing distance
a bit less than a foot worked well. However, at that distance it was a real
chore to free-view, so he included a "prism" factor so I could basically
use "resting accomadation" without going cross or wall-eyed (sorry, I
don't know the correct terminology). When I first used 'em there was 
a real feeling that I *should* be doing something other than looking
straight ahead, but it took only a short time to get used to it. One nice
bonus on this was that he included the other corrections I needed for
astig and so forth. Since I chose big clunky frames at the one hour
shop, they didn't cost me much as I was on one of the "get a second pair free"
coupons. 

The only problem is that they are so strong (focusing at a distance of
less than a foot) that I can't see anything else while wearing them!
I kind of have to grope around on the table to find the cards to pick up.
If I ever do it again, I'd probably go to bi-focals (although those might
be a @#(*&@(^! to grind) with the bottom part being a more normal
perscription,
and maybe slightly stronger prism on the top (stereo) part since I still
am not totally at the "resting point" (I have to go slightly wall-eyed - I'd
prefer totally neutral or slightly cross-eyed)

The fellow said he hadn't written a perscription like that since medical
school :-)

Just for curiosity sake, here's what I got...

O.D. Sph -1.25 Cyl +0.25 Axis 17 Prism 2^1 Base BO
O.S. Sph +0.50 Cyl +0.50 Axis 110   "        "

--Bob Wier



--- Bob Wier

  --- wier@xxxxxxxxxxxxxxxxx ---
     Rocky Mountain College
         Billings, MT
( currently in Ouray, Colorado)


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