An ocular or eyepiece lens assembly for a riflescope or spotting scope or other types of telescopic optical systems which may include a three element lens assembly comprised of materials of three different refractive indices, at least one of the lens elements composed of optical plastic material, for example, an acrylic polymer, and having at least one aspheric surface. In one configuration, the ocular includes a first lens component on the objective side which is a positive singlet lens element having at least one aspheric surface, and a second lens component on the eyepoint side (i.e. the side of the observer's eye), the second lens component being a doublet lens composed of a cemented lens pair. The singlet lens is configured to correct aberrations accumulated from the previous optics, such as for the objective lens assembly and the erector lens assembly of a riflescope, and also pre-correct the aberrations caused by the doublet lens located on the eyepoint side of the aspheric singlet lens. Preferably, the lens elements are composed of materials of three different refractive indices, with at least the singlet lens being composed of optical plastic material such as for example an acrylic polymer.