Every female character in the series (including in one brief shot the Statue of Liberty) wears glasses, hence the title.
The character designs are intended to both parody and glorify the meganekko fetish among many anime fans.
Other fetishes the anime uses include maids, sailor uniform, nurses, lolitas, and nuns.
However, a small region in Japan has successfully repelled them thanks to the development of "G-On" technology by the Grand Rifurekuto Amudo/Grand Reflect Armed (GRA).
This technology involves a band of girls (at first two, then three) who channel energy through special glasses.