"0"^^ . . . "optic axis"@en-us . "a line that passes through the center of curvature of a lens so that light is neither reflected nor refracted; \"in a normal eye the optic axis is the direction in which objects are seen most distinctly\""@en-us . . "106010105"^^ . "principal axis"@en-us . . . . . . "0"^^ . . . . "06010105-n"^^ . "105655281"@en-us . . "principal axis"^^ .