Vision Ease Lens and Carl Zeiss Vision have signed a royalty-bearing license agreement for freeform lens technology, under Carl Zeiss Vision International's U.S. patent number 6,089,713 and Australian patent number 739,849. The patents cover certain types of back-surface freeform progressive lenses and processes that are used to make them. These include progressive lenses whose front surfaces are rotationally symmetric, with the back-surface progressive design determined by prescriptions alone or in combination with other customizing options.