Feed Device for Bipolar Electrodes for Capsulotomy

The present invention relates to a feed device.

Bipolar wet field diathermy in microsurgery is described in "Klinische Monatsblatter fur Augenheilkunde" (Clinical Ophthalmology Monthly), May, 1984, vol. 5, pp. 331-512. The possibility of hemostasis in the vitreous humor was investigated, starting with the first vitrectomies in 1972. A coaxial bipolar diathermy device was developed as a suitable instrument for the purpose. However, it is necessary to make sure that the heating is not too high for operations on the eye. The device was consequently equipped with an aspiration infusion irrigation device at that time to remove emerging liquid blood. It was possible to close the then visible hemorrhage source by coagulation.

It was then almost logical to replace the previous procedure for opening the capsule of the lens, namely that of cutting open the capsule sac, opening the capsule sac by perforation and then tearing, or by capsulorhexis, by a diathermy technique.

Two instruments were disclosed for the diathermic opening of the capsule sac.

In U.S. Pat. No. 4,367,744, an electrically insulating handpiece carries a cauterizing ring, which is fed with electric power to the handpiece from behind by one wire. In order for it to be possible for a current to flow, it was proposed to conduct the procedure with two wires to the cauterizing loop. On applying the cauterizing loop to the lenticular sac, the current produces heat in a range of from 500.degree. C. to 2000.degree. C. Such a high temperature may act for only a short time, and the cauterized site on the lenticular sac must be cooled as quickly as possible. Because the cauterizing loop must be introduced into the eye in already hot state in order to be able to perform the operation in as short a time as possible, it is necessary to proceed extremely carefully, in order not to injure any other parts of the eye.

U.S. Pat. No. 4,481,948 describes a cauterizing loop of similar type, but which is not heated with current flowing in the loop. A high-frequency 10 khz current is instead fed to the loop. An opposite pole is placed beneath the patient in order to close the circuit. The physician switches on the high-frequency circuit by means of a pedal.

High heat, which can be very injurious to the eye tissue, can also result with this arrangement. According to the older patent, the hot loop had to be introduced into the aqueous chamber until it could then be placed through the pupil into the posterior chamber onto the lenticular sac, in order to cauterize an opening there.

It is possible to activate, i.e., heat the loop with the high-frequency current as desired by the physician. The high-frequency current then can flow only when the loop is placed on a site covered with conducting liquid, thus on the lenticular sac. It is not possible to control the heat acting to produce coagulation at the border of the opening by this effect, so that mild injuries can result from the action of the heat.

Consequently, an object of the invention is that of controlling the current feed so that only precisely as much heat is produced for cutting the lenticular sac and coagulating the border of the hole, but protecting other tissues against heat action without additional feed.

The invention is illustrated with the aid of drawings in an execution example below. The following features are shown:

FIG. 1 an enlarged segment of a human eye in section view;

FIG. 2 the same segment in perspective view with a bipolar diathermy instrument for capsulotomy;

FIG. 3 block diagram of a feed device for the bipolar diathermy instrument; and

FIG. 4 two pulse diagrams for current flow from the feed device.

FIG. 1 shows a front section of human eye 1 in greatly enlarged scale. This section clearly shows aqueous chamber 10, which is sealed off outside by cornea 11. The lenticular capsule consists of capsule sac 12, nucleus lentis 15, and cortex 14 lying between. Dilated iris 17 lies above. Pupil 16 forms a large opening. Posterior chamber 13 is located behind iris 17. Lenticular sac 12 with lens 15 lies between iris 17 and sclera 18.

FIG. 2 shows a view of eye 1 after FIG. 1 from obliquely above, so that the entire iris 17 is visible. Cornea 11 is sectioned at its edge 11a in order to create an access to aqueous chamber 10. Section 11b is held together by loop 11c on both sides, so that it cannot tear. Bipolar diathermy instrument 20 is introduced through this slit with handpiece 21, from which bipolar tip 23 protrudes. This bipolar tip 23 is bent in order for the instrument to be introduced at the side of eye 1 and parallel to lenticular sac 12 up to the section site, where section 12a can then be made in lenticular sac 12 with bent tip 23.

The physician can now coagulate lenticular sac 12 with high-frequency current reaching bipolar tip 23, or coagulate and sever with higher electrical feed. The severing runs into the difficulty mentioned at the outset, due to strong heating of the area around the working field.

A feed device (FIG. 3) with which a pulse duration modulation high-frequency current can be produced is now provided according to the invention. The feed device accordingly includes high-frequency generator 30 and pulse duration control 31, which is fed at rated value input 32 with a control voltage of 0 to +5 v, for example. The output 33 of high-frequency generator 30 and the output 34 of pulse duration control 31 are fed to inputs 36 and 37 of AND gate 35, whose output 38 is connected to input 39 of power amplifier 40. Power amplifier 40 is fed at input 41 from stabilized voltage source 42. The voltage source provides a current of 3 amp. at 18-v voltage. It includes short-circuit monitoring. Outputs 43, 44 are fed to the primary winding 45 of transformer 46. Lines 48, 49 lead from its secondary winding 47 to handpiece 21 of bipolar diathermy instrument 20.

It is possible to synchronize the high-frequency voltage with a frequency of 500 khz, for example, by this arrangement by selecting a control voltage of from 0 to 5 v, so that a constant frequency rectangular signal with a frequency of 30 hz and consequently with a pulse duration t.sub.p of 3 to 11 ms and a pulse pause t.sub.i of 22 to 30 ms is produced at a control voltage of 0.5 to 5 v, with which the AND gate is synchronized. At higher control voltage, the pulse becomes longer and the pulse pause correspondingly shorter (FIG. 4). The frequency of the rectangular oscillation remains constant. Power amplifier 40 can be fed by connection in AND gate 35. It can release a pulse output of P.sub.max =54 w by means of the stabilized voltage. The tissue of the lenticular sac is severed by this high pulse output, so that more than coagulation is achieved. The method of feeding high-frequency pulses with a pulse pause which lasts at least twice as long as the pulse permits a sufficiently long cooling not to endanger the adjacent tissue. The capsulotomy handpiece is insulated from the device by the transformer, so that no potential burdened with grounding is present in this instrument. An ionizing solution, for example Healon, is required in order for the high-frequency current to be able to flow at all between the poles of the bipolar diathermy instrument.