Dear Gareth,

Is your strabismus intermittant?

If that is the case, and you preceved objects as described below --
the
perhaps you are "improving" -- as you suggest.

Enjoy,

Stereopsis

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Stereopsis (from stereo meaning solidity, and opsis meaning vision or
sight) is the process in visual perception leading to the sensation of
depth from the two slightly different projections of the world onto
the retinas of the two eyes. The differences in the two retinal images
are called horizontal disparity, retinal disparity, or binocular
disparity. The differences arise from the eyes' different positions in
the head. Stereopsis is most commonly referred to as depth perception.

Contents [hide]
1 History of stereopsis
2 Popular culture
3 Geometrical basis for stereopsis
4 Computer stereo vision
5 Computer stereo display
6 See also
7 Bibliography
8 References
9 External links

[edit] History of stereopsis
Stereopsis was first described by Charles Wheatstone in 1838. ”… the
mind perceives an object of three-dimensions by means of the two
dissimilar pictures projected by it on the two retinæ…”.[1] He
recognized that because each eye views the visual world from slightly
different horizontal positions, each eye's image differs from the
other. Objects at different distances from the eyes project images in
the two eyes that differ in their horizontal positions, giving the
depth cue of horizontal disparity, also known as retinal disparity and
as binocular disparity. Wheatstone showed that this was an effective
depth cue by creating the illusion of depth from flat pictures that
differed only in horizontal disparity. To display his pictures
separately to the two eyes, Wheatstone invented the stereoscope.

Leonardo da Vinci had also realized that objects at different
distances from the eyes project images in the two eyes that differ in
their horizontal positions, but had concluded only that this made it
impossible for a painter to portray a realistic depiction of the depth
in a scene from a single canvas.[2] Leonardo chose for his near object
a column with a circular cross section and for his far object a flat
wall. Had he chosen any other near object, he may have discovered
horizontal disparity of its features.[3] His column was one of the few
objects that projects identical images of itself in the two eyes.

Stereopsis became popular during Victorian times with the invention of
the prism stereoscope by David Brewster. This, combined with
photography, meant that tens of thousands of stereograms were
produced.

Until about the 1960s, research into stereopsis was dedicated to
exploring its limits and its relationship to singleness of vision.
Researchers included Peter Ludvig Panum, Ewald Hering, Adelbert Ames
Jr., and Kenneth N. Ogle.

In the 1960s, Bela Julesz invented random-dot stereograms. [4] Unlike
previous stereograms, in which each half image showed recognizable
objects, each half image of the first random-dot stereograms showed a
square matrix of about 10,000 small dots, with each dot having a 50%
probability of being black or white. No recognizable objects could be
seen in either half image. The two half images of a random-dot
stereogram were essentially identical, except that one had a square
area of dots shifted horizontally by one or two dot diameters, giving
horizontal disparity. The gap left by the shifting was filled in with
new random dots, hiding the shifted square. Nevertheless, when the two
half images were viewed one to each eye, the square area was almost
immediately visible by being closer or farther than the background.
Julesz whimsically called the square a Cyclopean image after the
mythical Cyclops who had only one eye. This was because it was as
though we have a cyclopean eye inside our brains that can see
cyclopean stimuli hidden to each of our actual eyes. Random-dot
stereograms highlighted a problem for stereopsis, the correspondence
problem. This is that any dot in one half image can realistically be
paired with many same-coloured dots in the other half image. Our
visual systems clearly solve the correspondence problem, in that we
see the intended depth instead of a fog of false matches. Research
began to understand how.

Also in the 1960s, Horace Barlow, Colin Blakemore, and Jack Pettigrew
found neurons in the cat visual cortex that had their receptive fields
in different horizontal positions in the two eyes.[5] This established
the neural basis for stereopsis. Their findings were disputed by David
Hubel and Torsten Wiesel, although they eventually conceded when they
found similar neurons in the monkey visual cortex. [6] In the 1980s,
Gian Poggio and others found neurons in V2 of the monkey brain that
responded to the depth of random-dot stereograms.[7]

In the 1990s, Christopher Tyler invented autostereograms, random-dot
stereograms that can be viewed without a stereoscope.[8] This led to
the popular Magic Eye pictures.

Tbe short answer is, I don't know. I do remember reading about
experiments with cats maybe about 40 years ago in the Scientific
American.

Bill

There were news articles a few years ago about a vision scientist (Sue
Berry) who regained her stereo vision at age 48, in response to vision
training provided by an optometrist.

That was newsworthy because the accepted wisdom (ODs, MDs, PhDs) says that
adults can't do it.

The speculation is that "Stereo Sue" actually learned some stereopsis as an
infant or toddler, then lost it.

I'm not aware of any other verifiable reports of success. I wouldn't
recommend getting surgical alignment on the prospect of learning stereo.

-MT