Apparatus is provided including a frame configured to be worn on a face, such that a portion of the frame is located in front of a first eye and not in front of a second eye. The apparatus also includes a first lens, including one or more first lenses, coupled to the portion of the frame, and a second lens system, including one or more second lenses, coupled to the portion. A transparency regulation element coupled to the first lens system has variable transparency, and is configured to enhance viewing through the second lens system. A power unit is configured to drive the transparency regulation element to darken the first lens system without substantially darkening at least a portion of the second lens system during a first period, and, during a second period after the first period, to not drive the transparency regulation element to darken the first lens system.