Currently most plastic lenses and optical surfaces are still inspected directly by eyes by inspectors. In this paper, a Total Internal Reflection (TIR) illumination based dark-field inspection is analyzed and designed to enhance the visibility and contrast of the defects on the two surfaces of and inside the plastic lenses, and a lens inspection prototype is developed. Some trial testings have been conducted with the prototype, and the testing results are compared with those obtained from manual inspection directly operated by inspectors. The TIL dark-field inspection technique and feasibility to detect the popular defects of plastic ophthalmic lenses are verified and evaluated.