Recently, the existence of a perfect lens has been predicted, made of an artificial material that has a negative electric permittivity and a negative magnetic permeability. For optical frequencies a poormans version is predicted to exist in the sub-wavelength limit. Then, only the permittivity has to be negative, a demand that metals fulfill at optical frequencies. We propose a new measurement scheme to verify the performance of such a negative permittivity near-perfect lens at optical frequencies. The scheme is based on near-field scanning optical microscopy and single molecule detection. Prerequisite near-field single molecule data, necessary to assess the performance of the lens, is presented. A numerical evaluation, which includes absorption, of the expected performance of a slab of a realistic negative permittivity material confirms the merits of the scheme.