Is it true that if you wear glasses that are at the exact same
prescription that your eyes are at (or stronger), then your vision will slowly
worsen? If so, why? Or why not?

I asked the same question to my eye doctor and he agreed that wearing
glasses a little less strong than you need keeps your eyes stronger.
You are giving them exercise. He mentioned some research and opinion
by another eye doctor. Try it out yourself. You can fit yourself, at
the $1.00 store, with different strengths and notice what the effect
is. Don't you find that when you try to read without glasses your
vision gets clearer? Although this may be generally true I do not know
if it is true in your case.

This may be of interest:

http://answers.google.com/answers/threadview?id=303618

There is a disconnect between the medical answer of "eye strength" and
what people perceive this issue to be.  The average person believes
that the eye looses strength over time and that is why it is more
difficult to read close up, adjust to far and near sight rapidly, and
objects become "foggy" or blurred over time.  However, from a medical
perspective, this is not the case.

Most changes with vision occur with changes in the actual physical
composition of the cornea and lens of the eye.  A little known fact
(for most people) is that most of the focusing of your vision happens
in the cornea (the outermost layer of the eye) and not the lens.  This
is why surgeries such as RK are able to provide such dramatic
improvements in vision.  Some of the changes that affects vision
includes cornea shape changes, alterations in lens clarity (cataracts)
or shape, aging changes to the retina, and muscle weakness.

The muscles of the eye are in almost constant use, whether or not you
have coke bottle eyeglasses or mild drugstore reading glasses.  Not
wearing the correct prescription, however, can lead to eye strain,
excessive fatigue, headaches, and dizziness. On the other hand,
wearing the wrong eyeglasses does not lead to permanent