One my supposition is that during the reading there is
very intensive two-directional signalling between eye and
brain. So generally you are correct, the eye is technically
a camera attached to the brain and simply sends pictures
at some frequency to the brain.
But I would tend to think that it is not so simple actually.
You probably have heard sometimes users who claim something like:
"this text hurts my eyes"
For example if you read non-antialiased text and with too
high contrast, you'll notice that something is indeed going wrong
with your eyes.
This can happen probably because the brain starts to signal
the eye control system "something is wrong, stop doing it"
Since your eye cannot do anything with wrong contrast on
your screen and you still need to continue reading, this
happens again and again. This can cause indeed unwanted
processes and overtiredness of muscles inside the eye.
> And it also makes no sense that it would cause visual impairment, either.
> Comparing glyphs is a higher-level task in the brain,
> it has little to do with your eyes.
You forget about that whith illegible font or wrong contrast
for example you *do* need to do more concentrarion,
This causes again your eye to try harder to adopt
to the information you see, reread, which again
affects your lens and eye movements.