Patent Application
20080125695
The present invention generally pertains to controlling reflux in microsurgical systems and more particularly to controlling reflux in ophthalmic microsurgical systems.
During small incision surgery, and particularly during ophthalmic surgery, small probes are inserted into the operative site to cut, remove, or otherwise manipulate tissue. During these surgical procedures, fluid is typically infused into the eye, and the infusion fluid and tissue are aspirated from the surgical site. These probes have small orifices that are easily clogged with tissue. Such clogging is typically referred to as “occlusion”, “tip occlusion”, or “port occlusion”. The process of clearing such occlusions is typically referred to as “reflux”.
More generally, reflux is the ability to reverse the direction of the aspiration flow in a surgical system. Reflux may also be used for visualization of the surgical site (e.g. by moving blood and other tissue away from a particular point of interest).
A traditional method of reflux is to create a backpressure pulse of fluid that travels through the aspiration circuit to the tip or port of the probe to clear the incarcerated tissue. A hammer or valve is used to pinch a silicone tube to create a positive pressure pulse. This approach has no ability to control the reflux pressure profile. Therefore, a need continues to exist for an improved method of controlling reflux in a microsurgical system.
The present invention provides improved apparatus and methods for controlling reflux in a microsurgical system. In one aspect of the present invention, an apparatus for controlling reflux in a microsurgical system includes a pressurized gas source, an aspiration chamber fluidly coupled to the pressurized gas source and containing a fluid disposed therein, a first valve fluidly coupled to the pressurized gas source and the aspiration chamber, a second valve fluidly coupled to the pressurized gas source and the aspiration chamber, an accumulator fluidly coupled to the pressurized gas source and the aspiration chamber between the first valve and the second valve, a pressure transducer fluidly coupled to the accumulator, and a computer electrically coupled to the first valve, the second valve, the accumulator, and the pressure transducer. The apparatus creates a reflux pressure pulse in the aspiration chamber by the computer maintaining the first valve in an open state and the second valve in a closed state, allowing pressurized gas to flow from the pressurized gas source through the first valve to form a pre-charge reflux pressure in the accumulator, closing the first valve, opening the second valve to discharge the pre-charge reflux pressure into the aspiration chamber, and re-closing the second valve. In another aspect of the present invention, the above-described apparatus creates a steady state reflux pressure in the aspiration chamber by the computer maintaining the first valve and the second valve in an open state, the pressure transducer determining an actual pressure within the accumulator and providing a first signal corresponding to the actual pressure to the computer, the computer comparing the actual pressure to a desired pressure within the accumulator, and the computer providing a second signal to adjust the proportional valve in response to the comparison of the actual pressure to the desired pressure.
For a more complete understanding of the present invention, and for further objects and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawing, in which
The preferred embodiment of the present invention and its advantages is best understood by referring to
The aspiration circuit of
A user may input a setpoint for the desired pressure in accumulator 16 via interface 50. A user may also input whether a steady state reflux pressure or a pulsed reflux pressure is desired via interface 52. Alternatively, microprocessor 30 may provide a pre-defined reflux pressure profile for accumulator 16. Pressure transducer 46 measures the actual pressure within accumulator 16 and provides a corresponding signal to microprocessor 30 via interface 48. Microprocessor 30 compares the signal provided by pressure transducer 46 to the currently desired pressure for accumulator 16 and then adjusts proportional valve 14 via a signal over interface 56 so as to keep the measured reflux pressure of accumulator 16 at or near the desired reflux pressure.
When a steady state reflux pressure is commanded, microcontroller 30 maintains isolation valve 18 in an open position via a signal over interface 54. Microcontroller 30 then controls the reflux pressure within accumulator 16, aspiration chamber 22, and port 62 of surgical device 26 as described above. Since aspiration port 24 is located at the bottom of aspiration chamber 22, aspiration chamber 22 functions as a reservoir to provide sustained reflux, if necessary.
When a pulsed reflux pressure is commanded, microprocessor 30 momentarily closes isolation valve 18. Microprocessor 30 regulates the actual pressure within accumulator 16 as described above to create a “pre-charge” reflux pressure. Microprocessor 30 then closes proportional valve 14, opens isolation valve 18 to discharge the pre-charge reflux pressure in accumulator 16, and then re-closes isolation valve 18. In this manner, microprocessor 30 generates a pressure pulse that travels to aspiration chamber 22 and port 62 of surgical device 26. Such a pressure pulse is fully repeatable and programmable based upon the pre-defined reflux pressure profile stored in microprocessor 30.
Accumulator 16 also functions as a safety device. Once proportional valve 14 is closed, the maximum reflux pressure delivered to aspiration chamber 22 and port 62 is limited by the volume of accumulator 16 and the pre-charge reflux pressure.
The present invention is illustrated herein by example, and various modifications may be made by a person of ordinary skill in the art. For example, while the present invention is described above relative to reflux control in an ophthalmic microsurgical system, it is also applicable to other microsurgical systems.
It is believed that the operation and construction of the present invention will be apparent from the foregoing description. While the apparatus and methods shown or described above have been characterized as being preferred, various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the following claims.
