Four Eyes

 is a Trait which only appears in Fallout: New Vegas.

Effects

 * Taking this trait effectively lowers your base Perception by 1 point, when attempting to qualify for perks. This means the player must have a base perception of 7 to qualify for all perception based perks (except Infiltrator which requires 8 instead of the usual 7 due to the -1). This can be achieved by taking perception 7 at creation, or perception 6 with Intense Training added later to boost it to 7.
 * Wearing glasses with this trait will actually raise perception by +2 as seen in the pip-boy display, thereby nullifying the -1 in terms of accuracy benefits, compass benefits and skill benefits (though not the damage to base perception, thus requiring the player have 1 more point of permanent perception to take an associated perk). Perception 7 at creation, with this perk (glasses equipped), Intense Training +1 and a +1 perception hat will still total 10 perception.

Behind the scenes
This trait's name could be a reference to the film Six-String Samurai, which is about a spectacled man named Buddy (referred to as "Four Eyes" by many of the characters) traveling through a post-apocalyptic wasteland outside of 'Lost' Vegas.