What is "birth control glasses"

alt. (context plurale tantum US military slang English) The brown-framed prescription eyeglasses issued to new recruits in the U.S. Military, and perceived as notoriously unattractive. n. (context plurale tantum US military slang English) The brown-framed prescription eyeglasses issued to new recruits in the U.S. Military, and perceived as notoriously unattractive.