The invention relates to non-corrective unitary lens eyeglasses and safety helmets comprising a one-piece shield as well as a method for designing and fabricating such a one-piece shield. The method according to the invention for designing a one-piece shield (300) for non-corrective unitary lens eyeglasses or safety helmets, whereby said shield (300) has a front surface (302) and a back surface (304), is computer-implemented and comprises the following steps: - providing a front surface geometry of said shield (300)； - providing a predetermined local relationship of said front surface geometry with respect to a predetermined center of rotation of at least one of a wearer's eyes - calculating a predetermined portion (307a, 307b) of a back surface geometry of said shield (300) attributed to said at least one of said wearer's eyes by establishing non-zero minus power and minimizing prism as worn for a plurality of wearer's lines of sight intersecting said back surface (304) within said predetermined portion (307a, 307b) and said front surface (302) due to eye rotations of said at least one of said wearer's eyes around said predetermined center of rotation of said at least one of said wearer's eyes, whereby said predetermined portion (307a, 307b) of said back surface geometry is a freeform surface geometry.L'invention concerne des lunettes à verres unitaires sans correction et des casques de sécurité comprenant un écran d'un seul tenant, ainsi qu'un procédé de conception et de fabrication d'un tel écran d'un seul tenant. Le procédé selon l'invention de conception d'un écran d'un seul tenant (300) pour des lunettes à verres unitaires sans correction ou des casques de sécurité, ledit écran (300) ayant une surface avant (302) et une surface arrière (304), est mis en œuvre par ordinateur et comprend les étapes suivantes : - fourniture d'une géométrie de surface avant dudit écran (300) ； - fourniture d'une relation locale prédéfinie de ladite géométrie de surface avant par r
