Kpop idols wear circle lenses for a variety of reasons: a new concept, for fashion, a magazine shoot or they just use it daily for prescription.
Many Kpop idols use contact lenses for style and fashion. Beforehand, contact lenses were too pricey and were usually bought by people who wanted an alternative to eye glasses and they came in limited colors. Contact lenses now have a lot of variety in color and style, from transparent ones to cat eyes.
SNSD's YoonA

2NE1's Park Bom
f(x)'s Amber

4Minute's Hyuna
Red Velvet's Wendy

VIXX's Ken

SHINee's Jonghyun
INFINITE's Sungjong
EXO's Sehun

Big Bang's G-Dragon