noun
fashion glasses; non-prescription glasses; fake glasses
Glasses worn purely for style, with plain or no lenses. Often called 'fake glasses' or 'lensless glasses' in English.
彼女は伊達眼鏡をかけて、知的な印象を与えている。
She wears fashion glasses to give an intellectual impression.
この伊達眼鏡はレンズが入っていない。
These fashion glasses have no lenses.
伊達 (date) refers to stylishness or dandyism, from the Date clan of Sendai known for flamboyant fashion. Combined with 眼鏡 (megane, glasses), it literally means 'stylish glasses'.