Abstract: A liquid crystal lens drive circuit for a pair of spectacles has user-controllable components which can be used to adjust a response time of the circuit to changes in ambient light and to adjust the particular response of the circuit to excess light above a threshold in accordance with a desired response characteristic. Momentary changes in the light level from the general ambient can be prevented from changing the optical density of the lenses unnecessarily, and individual preferences as to the darkening characteristics can be accommodated in a standard pair of spectacles.