The lens opacity meter, a new instrument for quantifying the lens opacity, is described. The basic concept is the measurement of stray light produced by the lens. The measurement can be performed without dilating the pupil. A modulation of the light source renders the measurement insensitive to the surrounding light. The handling of the instrument is very simple. It is mounted on a slitlamp-like table. After adjusting the instrument to the eye, the measurement is initiated by depressing a console button.