Customer: I like these glasses. They make me look more smarter!
Customerís boyfriend: Yeah, well looks can be deceiving.
— Not Always Romantic
In the media, smart characters have a tendency to wear glasses. The association with the Hollywood Nerd archetype helps in modern works, although this trope is possibly older than that. May be Truth in Television, as some say that since smarter people typically do more reading, they place more strain on their eyes and are more likely to develop myopia (nearsightedness). Some studies have gone so far as to claim that myopia itself is linked with open-mindedness and intelligence. On the other hand, glasses are expensive, so people wearing them will not risk them in sports or fights (but some may use contact lens instead).
In anime, there is a commonly-used variant of this called Glasses-Kun: A Lancer who has black hair, is taller than The Protagonist, is always smarter than the main character, is relatively quiet, somewhat broody, and wears glasses.
In Real Life, there are lots of different types of people who wear glasses, but in fiction they are more rare. This is due to problems such as glare from the cameras in Live Action media, difficulty reading facial expressions, etc., and is the reason why when such characters are present it seems more significant. As proven by the examples, it is also why this trope occurs more so in Live Action, animated programming, and other pictorial media and less so in literature; it's a visual cue to the audience that the character is intelligent, yet is used sparingly because of the aforementioned difficulties involved.
This trope is an inherent part of The Glasses Gotta Go and Beautiful All Along, and often Hollywood Nerd. Supertrope to Nerd Glasses. The invoked form of this is Purely Aesthetic Glasses. Compare The Short Guy with Glasses.
Please do not list aversions, seeing as then it would be just a list of characters with glasses
Ishida Uryuu from Bleach wears glasses and is number one in his class. He also perfectly fits the description for a "glasses-kun". He takes after his father, Ryuuken, who also wears glasses and ends up being revealed to be so intelligent he can keep up with Urahara. To put that into perspective, even the hyperintelligent Big Bad Aizen admits that Urahara is the most intelligent shinigami alive. Urahara first realised Ryuuken was capable of keeping up with him when Ryuuken was only a teenager, and was stunned.
Both Franz Heinel and Shinsuke Maki in Future GPX Cyber Formula. One is a Gadgeteer Genius with cars and a computer expert, and the other is a computer machinist who makes computer games in his free time.
Played with in Detective Conan. Shinichi is already very smart without glasses, but as Conan, he wears glasses so he wouldn't be recognized as a younger version of Shinichi.
Minamo Kurokawa and Chika Kodama in Yubisaki Milk Tea, who are best and second best of their year, both wear glasses. Later Hidari Morii who Minamo teached as well.
In Axis Powers Hetalia, America's glasses are a hint that he isn't as stupid as he seems. One of his hobbies turns out to be archaeology.
Prof. Calculus (and quite a bunch of other scientists) from Tintin.
Klik and Teela from Pocket God are Gadgeteer Geniuses and are the only pygmies that wear glasses. Klik usually keeps on the top of his head, however.
Discussed in Superman: Secret Origin. When attempting to sell his old science books, Lex Luthor targeted Clark Kent, who had started wearing glasses, stating that glasses meant one of two things: genetic inferiority, or he read a lot. Somewhat subverted since in actuality, Clark's heat vision had just developed, and the lenses from the glasses shielded it in case it was accidentally triggered.
In Sucker Punch, both Dr. Gorski (in the asylum) and Blue (in the nightclub) have glasses, though they mostly only wear them when they need to take a closer look at something (They might merely be reading glasses, rather than corrective lenses). While Dr. Gorski is a psychologist, Blue is smart in that Dangerously Genre Savvy way.
Invoked by Elle Woods in Legally Blonde, when she dons glasses to appear smarter and more professional in order to help Paulette get her dog back.
Peter Parker, Richard Parker, Curtis Connors and Norman Osborn in The Amazing Spider-Man. Unlike in Raimi's movies, this version of Peter doesn't get his myopia cured by Spider-powers, so he keeps using glasses and contacts even after he's become Spider-Man.
You can tell that David Talbot in Queen of the Damned is intellectual, although not clever enough to accomplish much with his knowledge of vampires, by the fact his office looks like a library and he wears glasses which he draws attention to by taking them off and putting them back on a lot.
A weird example as it's something of an informed trait: scientist Bennett on Dollhouse wears, as Topher so gleefully puts it, "glasses. On a chain!" She's apparently far-sighted because she only wears them when looking at computer screens.
Garcia, a computer genius, and her boyfriend Kevin Lynch both wear glasses. Though he apparently switched to contacts, flashbacks to Reid's youth in Criminal Minds shows that he had some of the largest glasses any child has ever worn, ever.
And in an alternate universe episode where she never joined the SGC, we find Sam Carter wearing huge Nerd Glasses. Presumably in the regular timeline she just wears contacts. Either way, there's no denying that her (excellent) combat skills are NOT the reason she's on the team.
Alex Dunphy from Modern Family is the only one of the Dunphy kids to wear glasses, and is definitely the brains of the family.
Ted Kasselbaum, the resident private investigator and genius computer hacker on Just Cause, wears glasses with blue tinted lenses.
Peggy, a paralegal with three graduate degrees, also wears glasses.
Lampshaded in the first episode of Dollhouse, when Echo's programmed personality is a hostage negotiation specialist. Topher explains that the glasses aren't to make her look smarter; her implanted personality is short-sighted and her intellect comes from the drive to overcome such imperfections.
Explicit use of the trope as symbolism: Ads for the mental-exercise website Lumosity show people giving testimonials while various background and foreground animations appear. In one of them, glasses are drawn on the speaker's face as she says the site helps her stay sharp.
Pol Pot hated intellectuals, so he had people killed for wearing glasses.
There is some (rather Machiavellian) justification for this beyond Insane Troll Logic, however. Eyeglasses, while not an extravagant luxury, would be hard to come by in a poor, non-industrialized country like Cambodia was. Anybody capable of affording them would almost certainly be involved, if only indirectly, in the exploitation of the lower classes.