Complex sentence: In 1922, DeZeng replaced No.574 with No.584, which he called the Phoroptor, a device which became so popular that the term became genericized, though often spelled phoropter.
Split into simpler sentences: In 1922, DeZeng replaced No.574 with No.584, and shortened the name to Phoroptor. This device became so popular that its name became genericized, though often spelled phoropter.