pair of sunglasses vs trifocals

pair of sunglasses

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

trifocals

noun
  • Spectacles with corrective lenses that have three different powers per eye. 

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