The present invention relates to a lighting device in the form of a matrix illumination system, comprising a transparent carrier plate provided with a plurality of LEDs, arranged thereon. The materials for the membrane electrode assembly are formed from sulfonated polymers. A source region of the first conductivity type is located over each body region. In one embodiment, the guide surfaces define a recessed region for acoustic couplant. The internal surface of the distal cryotip of the cryosurgical instrument is covered by a porous coating, which soaks completely one portion of the refrigerant. Reinforcing extends from the prefabricated portion to the poured-in-place portion.