Did free form must do rear surface?

[kids optical frame]

Did free form must do on rear surface with a spherical surface, why not with a spherical surface? Actually, there is Free Form "Distortion Reducer" progressives, as they use an exciting new technology called REAR SURFACE, which enables us to customize the lens design for individual prescriptions and various frame compositions comparative to the limitations of traditional lens manufacturing which can only be tailored for a broad category of wearers. And, Free Form Progressive Lens will ensure the widest fields of vision in comparison to traditional progressive lens manufacturing, as much as 50% larger viewing zones will be achieved with a Rear Surface progressive.