Being attracted to girls with glasses is a very common theme for the intelligent and sensitive male.
Almost anyone wearing glasses seems to look more intelligent. Society reinforces this stereotype on people from a very young age (through movies, television, and books). It is not actually true (and most people know this). But it is so deeply ingrained in most people's minds, that they let themselves believe it (unless they actively seek to challenge this notion). Intelligent men seek intelligent women (hence the attraction).
Women with glasses are often seen as more down to earth, or more approachable (another stereotype). In this modern world of cheap contact lenses and laser surgery, anyone wearing glasses seems to be more "real", and less concerned with appearances. This serves as a magnet for the sensitive male (who has grown weary of pretentious women who are only concerned about appearances).
Glasses draw attention away from facial flaws. In addition to covering a portion of the face itself, glasses also hide other blemishes simply by being there (your eyes are drawn towards the glasses). This is what I believe has been called "The Jewelry Effect". The glasses themselves may not be attractive, but the simple fact that they draw your eyes away from other flaws makes them one of the best accessories that any woman can own. (I have known several women who own "fake glasses" just for this reason).
A woman wearing glasses will often have her eyes subtly magnified by the lenses (or not so subtly if the lenses are thick enough). The human eye is one of the most naturally beautiful parts of anyones body. The glasses serve to emphasize this, making even plain brown eyes seem alluring. (One particular bespectacled ex-girlfriend of mine simply did not look "right" without her glasses on. Her magical eyes seemed somewhat normal without the benefit of her thick lenses).
Girls with glasses are slowly becoming an endangered species. Laser surgery for vision correction is getting better (and cheaper), all of the time. A hundred years from now people may think it quite strange for anyone but senior citizens to have glasses. At least our generation will still get to enjoy them.