A piston of an internal combustion engine includes a cavity for gases passing a piston ring and a first flow path leading from the cavity to a piston ring region and a second flow path extending from the cavity to an outlet opening for removing gases to an inlet opening in a cylinder wall in at least one piston position. On one surface of a glass substrate are successively laminated an ITO transparent electrode film and an EC device consisting of three layers of an anode compound film, a solid electrolyte film and a cathode compound film. A strap connected with the body is designed to engage the spinous processes, such that the device may be adjusted to be positioned about the spinous processes. Means for lighting is adjustably supported on an arm placed above the lens so that light from the lamp can shine through the lens and onto the surface of the reading materials.