has an article on: trifocals Wikipedia From tri- + focal (see focus). Coined by John Isaac Hawkins, their inventor, in 1826. trifocals pl (plural only)...
tri- + focal trifocal (not comparable) (optics) Of or pertaining to corrective lenses that have three different powers per eye. bifocal trifocals...
quadri- + focal quadrifocal (not comparable) (optics) Of or pertaining to lenses that have four different powers per eye. bifocal trifocal quadrifocals...
focal (see focus), coined in 1824 by John Isaac Hawkins, inventor of trifocals. When the concept of bifocals was originally conceived by Benjamin Franklin...
multifocals pl (plural only) Spectacles having several focusing areas that correct for both nearsightedness and farsightedness. bifocals trifocals...
-ɑsit Syllabification(key): kol‧mi‧te‧ho‧la‧sit kolmiteholasit (optics) trifocals “kolmiteholasit”, in Kielitoimiston sanakirja [Dictionary of Contemporary...
for distance vision and the other for near vision bifocality bifocals trifocal From bi- + focal. bifocal (feminine bifocale, masculine plural bifocaux...
relations of the muscles […] 1921 June, John A. Spengler, “Advantages of trifocal lenses and reasons why they should be worn”, in American Journal of Ophthalmology[1]...