varifocal
Concise Oxford English Dictionary © 2008 Oxford University Press:
varifocal /ˌvɛːrɪˈfəʊk(ə)l/
▶adjective denoting a lens that allows an infinite number of focusing distances for near, intermediate, and far vision. ▶noun (varifocals) varifocal glasses.
'varifocal' also found in these Oxford entries:

