Sorry, but most of the above answers are wrong IMHO. If you wear too strong minus glasses, it effectively makes you far-sighted, with the typical symptoms: it makes looking in the distance more tiresome since your eyes have to accomodate, and it may make reading impossible. If you wear too strong plus glasses, you won't be able to see in the distance. These things can not be corrected by the brain, since the brain can only handle what is on your retina, and if it is unsharp, information is missing. If you could get used to wearing too strong glasses, near- and far-sightedness could be cured, which is not the case, unfortunately. For farsigtedness, a distinction must be made between on the one hand juvenile farsigtedness which is caused by the geometry of the eye (too short or too flat), like nearsigtedness is caused by an eye that is too long - and on the other hand the farsigtedness of elder people, caused by an increasing inability to accomodate. Perhaps training can play a role here - or conversely, the lack of training due to too strong glasses.
Finally, young children usually are slightly farsighted, which is easily compensated by their strong ability to accomodate. This farsightedness disappears as they eyes grow. Strong farsighted young children will likewise observe a reduction in farsigntedness. It has been suggested that wearing glasses may impair this process, and keep children farsighted that otherwise would no longer have needed glasses when they get older. Animal experiments did not confirm this hypothesis. Furthermore, uncorrected strong farsightedness may cause problems that are far worse, like squiting and a lazy eye. A lazy eye is disconnected by the brain, so to say, so glasses correction wil not help if the lazyness has become irreversible.
