Abstract: A pulsed high frequency current is fed to a bipolar diathermy instrument for optimum execution of a section in capsulotomy. The pulse duration can constantly be altered between 3 ms and 11 ms, whereby a pause of 30 ms or 22 ms develops. This pause is sufficient to cool the instrument tip, flushed with sodium chloride, in order to prevent the possibility of injury to adjacent tissue. The pulse repetition frequency is about 15 hz. The device necessary for the purpose includes pulse duration control (31) and HF oscillator (30). The HF current is synchronized by pulses from control (31) with AND gate (35). Amplifier (40) feeds handpiece (21) of the diathermy instrument by transformer (46). The required operation free from grounding is thereby assured.