pair of glasses vs pair of sunglasses

pair of glasses

noun
  • A pair of lenses set in a frame worn on the nose and ears in order to correct deficiencies in eyesight or to ornament the face. 

pair of sunglasses

noun
  • A pair of glasses with tinted lenses designed to protect the eyes from sunlight. 

How often have the words pair of glasses and pair of sunglasses occurred in a corpus of books? (source: Google Ngram Viewer )