Jaap Frank wrote:
> The strain for your eyes is the wrong focusing and
> your brain must be learned to do this.

Or rather, your brain must unlearn what it has learned about the
relation between the angles of the eyes, and the correct focusing.
Normally, there is a constant relation between these, where a certain
distance to an object (which means a certain angle between the eyes)
corresponds to a certain focus depth. This is very much a reflex we
have, and thus it is difficult to make our brain use a different focus
for a certain depth, than the brain is used to.

The danger of training the brain to be able to focus incorrectly is that
the natural reflex is weakened. With the ability to focus incorrectly,
as it is needed to see stereograms, also comes the ability to focus
incorrectly in general (or unfocusing, rather). Some years back I was
very much into stereograms and learned to focus incorrectly with ease,
but ever since, I have suffered from the unfortunate side-effect, that
when I have to concentrate on something, but am a bit tired, my eyes
every so often go out of focus involuntarily, and also don't focus at
the same point. Not a huge problem of course, but still pretty annoying.

Rune
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rune|vision:  http://runevision.com (updated Oct 19)
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