A gas mask for normal pressure operation and overpressure operation allows changeover of the expiration valve from normal pressure operation to overpressure operation is made possible in a simple manner. Therefore it is advantageous to supply a high-resolution electrode array internal to the sclera, near the fovea and a lower-resolution electrode array eternal to the sclera near the periphery of the retina. The method provides lower cost and greater flexibility as compared with conventional ablation and etching processes of manufacturing of polymeric micro fuel cells. Between the outer bellow and the inner bellow, a compensation volume is confined, which is provided with a fluid connection to the volume of the subsea device. A power supply is connected to the separating electrode.