You are indeed entitled to a copy of your medical record.  However, a copy
of the record is *not* the same as a valid prescription.  In the same
vein, your record might say that the doctor prescribed codeine for your
broken toe last year; a copy of the record wouldn't let you buy another
supply now.  Paying for that one office visit doesn't get you unlimited
refills...

There are a variety of reasons why a doctor won't release a contact lens
prescription.  One is economic--he wants you to buy from him.  Fitting is
frequently done at less than cost and the doctor expects to make money
from other exams and sales (contacts, sunglasses, supplies...).  However,
there are valid medical reasons as well.  Contacts are medical devices
that rub all over your eyes all day.  As fit changes, you can develop a
myriad of problems (such as new blood vessels growing into the cornea or
allergic/irritation reactions under the eyelids)--your doctor may want to
see you *not to make money* but to make sure than nothing bad is
happening.  There are those who would say that continually refilling a
medication or contact prescription without examining the patient is a form
of poor (if not mal-) practice.

Can you do it anyway?  Some mailorder firms (they're all in the 800 phone
directory and advertise in magazines and the Wall Street Journal for
example) have doctors that will look at your record and write a
prescription without seeing you.  I'm not sure this is a great idea but it
is done.

Jerry

GStr...@aol.com

It is in your best interests to have an exam, bring everything up to date
and move on. There are laws preventing most eyecare professionals from
filling Rxs that are over a certain date ie 2 years usually. It's not real
smart to try to save a few bucks now and have a contact lens related
problem that can do real damage. See your Doc.

Noll Paynter, OD
Seattle

I was recently introduced to the "Magic Eye" pictures, in which you see
stereo images if you look with the proper degree of divergence or
convergence.  Otherwise, you see meaningless patterns.  This was very
fascinating, as I had never seen these pictures before.

After letting my eyes go out of focus, after a couple of minutes I was able
to see the stereoscopic effects in the pictures.  I was able to hold this
for a few sections, but then I would lose it.   It was very difficult to
get the effect back.  It appears that it would take a bit of practice to be
able to do this consistently.

I got a slight headache trying to pull in those images in stereo, but
later in the evening I noticed an increased stereoscopic ability in
general in whatever I was looking at (not the pictures).  My left eye is
much, much more myopic than my right eye, and always has been.  I was told
once that I couldn't see stereo vision in "the right way" due to this.

My question is this:  if I practiced looking at these Magic Eye pictures
periodically, would my stereoscopic vision ability be improved?
Anyone know the history of the "Magic Eye" pictures?

Judy Lender
len...@rand.org

They originated in some research studies by Bela Julesz of Bell Laboratories
on how binocular perception works.  (Does Bell Labs still do psychology
or is that another terrible casualty of deregulation?  What a horrible
feeling to read that they had closed the radio astronomy division).

Binocular vision relies on being able to detect very small differences in
the images seen by each eye, specifically the relative alignments of near
and far objects.  The question he was studying was whether you _first_
pick out the objects and outlines, _then_ compare their alignments, or
whether binocular disparity is sensed at some lower, more fundamental
level.

The research technique he used was to generate computer images, called
"random dot stereograms," in which each image individually consisted of
random dots, hence had _no_ contours or objects to pick out.  The stereo
pair would be almost identical, but perhaps within a square area all of
the dots would be slightly shifted over.  To everyone's surprise--well,
_mine_ anyway, but maybe not Julesz's--these pairs gave a stereo effect,
showing that binocular disparity did NOT depend on detecting objects or
outlines.

A few years ago, someone figured out how to make the single-image kind,
and the computer hackers got involved and discovered it was fun.  I think
they may have been partly influenced, directly or indirectly, by
Kenneth Knowlton, also of Bell Labs, who for years has made half-tone
images in which the half-tone dots are, in fact, other images.  (For example,
at Wang Labs he created a portrait of An Wang by selecting seashells of
varying sizes and degrees of lightness and mounting them on a black
background, each seashell equalling one half-tone dot).  

As a kid, I used to enjoy staring at repetitive patterns, like chickenwire,
chain-link fence, or the then-still-popular hexagonal-tile bathroom floor.
By doing something with my eyes similar to what you do with the Magic Eye
pictures, I could get some interesting sensations--mostly it was just weird
to see the pattern fuse again, but of course it would also seem strangely
closer and smaller...

Incidentally, one of the early Julesz experiments involved a Julesz pair
in which one member of the pair had been thrown out of focus.  You still
saw a stereo effect.  

As a matter of curiosity, how much difference is there in your eyes?
My right eye is about three diopters more nearsighted than my left eye.
One optometrist seemed to be mildly skeptical when I told her my
binocular perception was excellent, until she tested it.

--
Daniel P. B. Smith
dpbsm...@world.std.com

dpbsm...@world.std.com (Daniel P. B. Smith) writes:

I believe there are some people doing applied human-factors stuff, but
the psychologists that used to work in the old Acoustics, Speech and Signal
Processing division are all gone.  Julesz is now on the faculty at
Rutgers.

The "someone" who intvented the autostereogram
was Christopher Tyler, one-time postdoctoral associate of Julesz
at Bell Labs, and now a codirector of the Smith-Kettlewell Institute for
Visual Science in San Francisco.
It was a lot more an a few years ago, maybe when he was
at the labs in the 70's.  He refrained from publishing anything on
it for a number of years.

--

        Jeff Mulligan (j...@vision.arc.nasa.gov)
        NASA/Ames Research Ctr., MS 262-2, Moffett Field CA, 94035-1000
        (415) 604-3745

You do need to have stereo vision to perceive them. This means you need to
have reasonable vision in both eyes. Approximately 5% of the population have
a  problem with stereopsis because of conditions such as strabismus (squint),
anisometropia (a significant difference in the refraction between the eyes),
other causes of a lazy eye, or poor vision in one eye for example after
scarring of the retina.

People with nystagmus may have problems because the vision isn't quite good
enough. In particular though, anyone who has nystagmus because they are
albino has different problems as well.
The usual wiring of the two eyes, is that some of the brains visual cells
receive input from both eyes. In albinos, all the cells are basically wired
to just one eye. Thus there are no cells able to process the normal
differences seen by the two eyes which is used to build up a 3 dimensional
image (stereopsis).

Keith G Davey BSc (Hons), DOpt, MB BS, FRCOphth
Optometrist & Ophthalmologist, UK

- sent via an evaluation copy of BulkRate (unregistered).

In article <3643932670.2653...@andyclin.andyclin.exnet.com>

I spent some time around stereoscopic exhibits in a science museum,
and got the impression that a lot more than 5% had trouble.  I didn't
keep notes though.  I asked one of the exhibit workers about this, who
thought that it was the order of 25%. Does anyone have good data on this?

Of course, Dr. Davey may have the right statistic for professional
conditions, in which the patient is provided with a stereoscope and
good instructions.  I've certainly found many people who had no
difficulty at all with a stereoscope, but were unable to manage the
proper convergence for the autostereograms.  One problem must be that
there's a conflict between the binocular convergence angle and the
focus. In a stereoscope, you can make these consistent -- e.g., focus
at infinity AND eyes directed out in parallel.

-- min...@media.mit.edu

.

Daniel P. B. Smith (dpbsm...@world.std.com) wrote:

: As a matter of curiosity, how much difference is there in your eyes?
: My right eye is about three diopters more nearsighted than my left eye.
: One optometrist seemed to be mildly skeptical when I told her my
: binocular perception was excellent, until she tested it.

: --
: Daniel P. B. Smith
: dpbsm...@world.std.com

Thanks for your most informative response.  My eye prescription is as
follows:

OD  -4.00  -0.25  X 175
OS  -5.00  -0.75  X 014

I haven't taken the time to learn what it all means yet, but as I
mentioned before, a doctor told me several years ago that my stereo vision
was not what it should be, because my left eye was much worse than my
right, so I was surprised that I could see the pictures at all.  Actually,
I see them best without my glasses.  Even then, my left eye is slightly
blurry by itself, but that sure isn't apparent when I use both eyes to see
the picture.

I've looked at these pictures the last couple of nights and it's getting
easier and easier to see them.  As I mentioned before, my stereo vision is
really enhanced all around after I've looked at these pictures.  It has to
be a good exercise.

Judy Lender
len...@rand.org

You know something, I absolutely hate those picture ! :)   As far as I
know, I'll never be able to see thom because of my nystagmus..  If anyone
know any different, I'd love to hear about it.

Adrian
--
/-------------------------------------------\  Two rules to success in life...
| Adrian Parker   adr...@willen.demon.co.uk |  1) Don't tell people everything
| Quondam Ltd     (+44) 01902 601157        |     you know.
\-------------------------------------------/  2)

Gawd! what a bunch of "ambulance chasers".  If you're worried about injury
from looking into a laser scanner - don't look into a laser scanner!  I'm
sure that one could suffer some kind of injury by concentrating on a 1000
watt mercury-vapor street light for a few minutes.  So sue god for making
light!  Call Norton-Frickup!  Write the "enquiring minds"!

OR ... just get a life?