a single pane, unitary lens defining upper and lower edges, the lower edge having a nosepiece opening formed therein for mounting the lens on a nose of a wearer,

the lens having a first arcuate cross-sectional configuration in a horizontal direction, the first arcuate cross-sectional configuration defining opposing lateral segments and a central zone interposed therebetween, the opposing lateral segments being oriented tangentially relative to the central zone, the lateral segments each having a first radius of curvature designated R₁, the central zone having a second radius of curvature designated R₂,

the lens having a second arcuate cross-sectional configuration in a vertical direction, the second arcuate cross-sectional configuration having a third radius of curvature designated R₃, the third radius of curvature increasing along the lens from a minimum at a center point of the central zone to a maximum in the lateral segments thereof,

wherein R₁≠R₂.