Lens aging has been measured in vivo using a new instrument: the lens opacity meter 701 (Interzeag, Schlieren, Switzerland). Statistical analyses have been performed to verify the occurrence of the phenomenon, the sex differences and the reproducibility of the obtained results. The findings demonstrate an increase in the light scattering in the normal lens with aging, which is similar in both sexes. The instrument detects this process and the measurements have a high degree of reproducibility.