The invention is directed to non-corrective unitary lens eyeglasses and safety helmets including a one-piece shield and a method for making such a one-piece shield. The method is for designing a one-piece shield for non-corrective unitary lens eyeglasses or a safety helmet, whereby the shield has a front and a back surface, and is computer-implemented with the steps: providing a front surface geometry of the shield； providing a local relationship of the front surface geometry with respect to a center of rotation of a wearer's eye； and, calculating a portion of a back surface geometry attributed to the wearer's eye by establishing non-zero minus power and minimizing prism. The portion of the back surface geometry is a freeform surface geometry.
