In 1884 B. M. Hanna was granted patents on two forms of bifocals which become commercially standardized as the "cemented" and "perfection" bifocals. Both had the serious faults of ugly appearance, fragility, and dirt-collection at the dividing line. At the end of the 19th century the two sections of the lens were fused instead of cemented At the turn of the 20th century, there was a considerable increase in the use of bifocals.