This paper introduces the differential geom-etry of curves in Euclidean 3-space, the motiva-tion being the writer's belief that, despite their fundamental importance, curves are inadequate-ly treated in optometric educational programs. Curvature and torsion are defined along a curve. Two numerical examples are presented. The fundamental theorem of curves is stated. The relationship of the geometry of varifocal lenses and curves known as involutes are discussed. A brief treatment of the theory

more »

... contact is given with suggestions of applications in contact between spectacle lenses and frames, contact lenses and corneas (including orthokeratology), intra-ocular lenses and structures in the eye, and spectacle frames and the face.