A control for an auto-darkening lens or other optical device monitors light incident on the viewing area or in relatively close proximity to the viewing area of the lens to provide accurate light sensing and to avoid inadvertent blocking of light to one or more light sensors. Reflectors, prisms, prism strips and the like may be used to direct light to the sensor(s). A method for detecting light incident on an auto-darkening lens and a method for controlling an auto-darkening lens direct light from the viewing area of an auto-darkening lens or from relatively close proximity to the viewing area to one or more sensors to detect such light and, accordingly, to control operation of the auto-darkening lens.