Patent Description:
Ophthalmic surgery frequently involves the removal of fluid and/or tissue from the eye and replacement of the material removed with a fluid such as a balanced salt solution (BSS). In order to remove material, a cannula connected to an aspiration line is inserted into an incision in the eye. The aspiration line is coupled to a console that includes electronics, a control system, a vacuum source such as a peristaltic pump and a fluid source. The vacuum source provides a vacuum to the aspiration line. The vacuum in the aspiration line causes material to flow from the eye and through the aspiration line. To maintain intraocular pressure, another cannula connected to an irrigation or infusion line is inserted into another incision in the eye. The irrigation line is connected to a fluid source in the console. The fluid source may be a reservoir of BSS that can be pressurized to greater than the ambient pressure. When the fluid source is pressurized, the fluid flows is forced out of the fluid source, through the irrigation line and into the eye.

During such surgery, it is desirable to isolate biological material removed from the eye from the vacuum pump. To do so, cassettes are used. A cassette typically fits within a receptacle within the console. Tubing from the aspiration line is connected to a port in the cassette. The cassette is connected to the vacuum source via another port. The vacuum source applies a vacuum to the cassette, which provides the vacuum to the aspiration line. The suction in the aspiration line causes biological material to flow from the eye into the cassette, where the biological material is stored. Thus, the biological material is isolated from the vacuum pump. To provide fluid to the eye, another cassette coupled to a pressure or fluid source and to the irrigation line may be used in an analogous manner.

A pressure sensor may be used to monitor pressure within the cassette during use. For example, a rubber membrane may flex in response to the internal pressure of the cassette. This deflection may cause the membrane to touch a contact sensor. Thus, the pressure may be determined. Alternatively, a sensor may provide light that is reflected off of the membrane at an oblique angle. The reflected light is provided to a sensor. Changes in the position of the light correspond to changes in the internal pressure.

There may be drawbacks to such mechanisms for measuring internal pressure of the cassette function. For example, use of reflected light may not provide sufficient sensitivity to the internal pressure. Further, the flexible membrane adds to the cost of each of the cassettes, which are disposable. Internal pressure sensors may be subject to the biological material removed from the eye. Thus, such sensors may fail. These sensors also add to the cost of the disposable cassettes.

Accordingly, what is needed is an improved mechanism for monitoring the internal pressure of a cassette in a surgical system.

Reference is made to documents <CIT>, <CIT> , <CIT>, <CIT> and <NPL>, which have been cited as representative of the state of the art.

It will be appreciated that the scope is in accordance with the claims. There is provided a system in accordance with claim <NUM>. Further features are provided in accordance with the dependent claims. The specification also provides description of methods, not claimed in the appended claim set, description of the methods being included for further information.

A method of the specification, the method not claimed in the appended claims, and system, the system in accordance with the appended claims, provide a surgical system including a cassette, a console and an interferometric pressure sensing system coupled with the console. The cassette is for exchanging material with a patient and includes a wall and a reflector. The wall undergoes a deflection in response to a nonambient internal cassette pressure. The console is coupled with the cassette. The interferometric pressure sensing system is coupled with the console. The interferometric pressure sensing system includes a light source and a detector. The light source provides a first portion of light that is reflected off of the reflector and a second portion of light that bypasses the reflector. The first portion and the second portion of light are recombined to form an interference pattern. The deflection corresponds to a shift in the interference pattern detectable by the detector. According to the appended claims, the cassette includes an internal pressure sensor, wherein the internal pressure sensor is configured to be used to measure an internal pressure of the cassette and calibrate the shift in the interference pattern to the deflection and to the internal pressure.

According to embodiments of the method and system disclosed herein the internal pressure of the cassette may be more accurately measured, may not require the use of sensors internal to the cassette and may not require expensive additions to the cassette.

The exemplary embodiments relate to surgical systems, such as consoles used in ophthalmic surgery. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the exemplary embodiments and the generic principles and features described herein will be readily apparent. The exemplary embodiments are mainly described in terms of particular methods and systems provided in particular implementations. However, the methods and systems will operate effectively in other implementations. Phrases such as "exemplary embodiment", "one embodiment" and "another embodiment" may refer to the same or different embodiments as well as to multiple embodiments. The embodiments will be described with respect to systems and/or devices having certain components. However, the systems and/or devices may include more or less components than those shown, and variations in the arrangement and type of the components may be made without departing from the scope of the invention. The exemplary embodiments will also be described in the context of particular methods having certain steps. However, the method and system operate effectively for other methods having different and/or additional steps and steps in different orders that are not inconsistent with the exemplary embodiments.

The method and system are also described in terms of singular items rather than plural items. For example, a single cassette having a single interferometric pressure sensing system is used and/or shown in some embodiments. One of ordinary skill in the art will recognize that these singular terms encompass plural. For example, multiple cassettes and/or multiple interferometric sensing systems might be used.

In certain embodiments, the system includes one or more processors and a memory. The one or more processors may be configured to execute instructions stored in the memory to cause and control some or all of the process(es) set forth in the drawings and described below. As used herein, a processor may include one or more microprocessors, field-programmable gate arrays (FPGAs), controllers, or any other suitable computing devices or resources, and memory may take the form of volatile or non-volatile memory including, without limitation, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), removable media, or any other suitable memory component. Memory may store instructions for programs and algorithms that, when executed by a processor, implement the functionality described herein with respect to any such processor, memory, or component that includes processing functionality. Further, aspects of the method and system may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects. Furthermore, aspects of the method and system may take the form of a software component(s) executed on at least one processor and which may be embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

A method and system provide a surgical system including a cassette, a console and an interferometric pressure sensing system coupled with the console. The cassette is for exchanging material with a patient and includes a wall and a reflector. The wall undergoes a deflection in response to a nonambient internal cassette pressure. The console is coupled with the cassette. The interferometric pressure sensing system is coupled with the console. The interferometric pressure sensing system includes a light source and a detector. The light source provides a first portion of light that is reflected off of the reflector and a second portion of light that bypasses the reflector. The first portion and the second portion of light are recombined to form an interference pattern. The deflection corresponds to a shift in the interference pattern detectable by the detector.

<FIG> depicts a perspective view of an exemplary embodiment of a surgical system <NUM> usable in ophthalmic surgery. <FIG> depicts a portion of the surgical system <NUM>. Referring to <FIG>, the surgical system <NUM> includes a console <NUM>, a cassette <NUM> and an interferometric pressure sensing system <NUM>. <FIG> are not to scale and for explanatory purposes only. Thus, the system <NUM> is not limited to a particular console <NUM>, cassette <NUM> or interferometric sensing system <NUM>. For example, although a particular location of the cassette <NUM> in the console <NUM> and geometry are shown in <FIG>, the surgical system <NUM> is not limited to the location and geometry depicted. For simplicity, not all portions of the console <NUM> are shown or labeled. The console <NUM> is coupled with the cassette <NUM> and the interferometric sensing system <NUM>. During use, the console <NUM> is also typically connected with a surgical handpiece (not shown). The surgical handpiece may include an aspiration line and/or irrigation line connected to the console <NUM> via tubing (not shown) and electronics that are connected to and controlled by the console <NUM>.

The console <NUM> includes a display <NUM>, associated electronics (not explicitly depicted or labeled), a vacuum/pressure source <NUM>, a receptacle <NUM> for receiving the cassette <NUM>, and detection unit <NUM>. In some embodiments, the console <NUM> may include both a vacuum source and a pressure source. In such embodiments, the sources are coupled to different cassettes that may reside in the same or different receptacles. However, for simplicity, the surgical system <NUM> is described in the context of a single receptacle <NUM>, a single cassette <NUM> and a single vacuum/pressure source <NUM>. The source <NUM> is primarily described in the context of a vacuum source <NUM>. An analogous the discussion applies for a fluid/pressure source. Although depicted as part of the console <NUM> in <FIG>, the detection unit <NUM> may be part of the interferometric pressure sensing system <NUM>. Detection unit <NUM> is communicatively coupled to interferometric pressure sensing system <NUM> and other components of system <NUM>. In certain embodiments, detection unit <NUM> may comprise one or more processors and memory configured to receive one or more signals from pressure sensing system <NUM> (e.g., signals indicating an interference pattern or shift in an interference pattern generated by detector <NUM>) and determine cassette pressure based on the received signal(s) based on stored data correlating shifts or changes in interference patterns with internal cassette pressure and/or wall deflection, as described herein.

The vacuum/pressure source <NUM> is coupled to the cassette <NUM> through the receptacle <NUM>. The vacuum/pressure source <NUM> may be a vacuum source such as a vacuum pump. In such an embodiment the vacuum source <NUM> provides a negative pressure (vacuum) to the cassette <NUM>, which provides a vacuum to the aspiration line. In other embodiments, the vacuum/pressure source <NUM> may be a pressure source that provides a positive pressure to the cassette <NUM>. The cassette <NUM> is coupled to a fluid source, which provides fluid to the irrigation line under the positive pressure. Alternatively, the vacuum/pressure source <NUM> may be a fluid source that can be placed under positive (greater than atmospheric) pressure.

The cassette <NUM> is for exchanging material with a patient. In the embodiment shown, the cassette <NUM> receives tissue, fluid and/or other biological material from the patient's eye. In other embodiments, the cassette <NUM> might be used to provide fluid such as a BSS to the patient's eye. The cassette includes walls and an internal chamber (not explicitly labeled in <FIG>). The cassette <NUM> also includes a reflector <NUM> that is shown in <FIG> (but not in <FIG>). The reflector <NUM> may be a mirror or any other suitable reflector. The reflector <NUM> may be attached to or integrated into the wall. In some embodiments, therefore, the wall itself may be reflective. In certain examples, the wall may be coated with or coupled to a reflective material. The cassette <NUM> is oriented such that the reflector <NUM> is facing the interferometric sensing system <NUM>. In the embodiment shown, the normal to the surface of the reflector <NUM> is perpendicular to the interferometric sensing system <NUM>. The reflector <NUM> may be at an oblique angle from some or all of the interferometric sensing system <NUM> in other embodiments.

Also shown are ports <NUM> and <NUM>. The port <NUM> may be connected to tubing (not shown) and, therefore, to a surgical handpiece. The port <NUM> is connected to the vacuum source <NUM>. Thus, a vacuum is provided to the cassette <NUM> through the port <NUM>, while suction is provided to the aspiration line via port <NUM>. Biological material from the patient's eye is received in the cassette <NUM> via port <NUM>. This biological material remains in the cassette <NUM>. Thus, the cassette <NUM> isolates the vacuum source <NUM> from the biological material.

The interferometric pressure sensing system <NUM> is coupled with the console <NUM>. In certain examples, the interferometric pressure sensing system <NUM> may be considered to be incorporated into the console <NUM>. Thus, the interferometric pressure sensing system <NUM> being coupled with the console <NUM> includes but is not limited to some or all of the components of the interferometric pressure sensing system being part of the console <NUM>. In other embodiments, the some or all components of the interferometric pressure sensing system need not be incorporated into the console <NUM>. In such embodiments, the light used may be transmitted to the appropriate location, for example via fiber optic cables. Also in such embodiments, control and data signals may be transmitted between the console <NUM> and the interferometric pressure sensing system <NUM> via wiring.

The interferometric pressure sensing system <NUM> includes a light source <NUM> and a detector <NUM>. The detector <NUM> may be a linear or areal detector array. In certain embodiments, detector <NUM> may include any suitable light detector (e.g., CMOS, CCD, etc.). In some embodiments, the light source <NUM> may include a laser. Multiple light sources might be used, particularly if the light produced is in phase and of the same wavelength. However, in general, a single light source <NUM> is present. The interferometric pressure sensing system <NUM> splits the light into a first portion and a second portion. In general a beam splitter or analogous component is used to split light from the source <NUM> into multiple portions. In <FIG>, these portions of light are shown as two separate beams <NUM> and <NUM> emanating from the light source <NUM>. However, one of ordinary skill in the art will recognize that the portions of light actually correspond to multiple beams having some physical width and slightly different trajectories.

A first portion of light <NUM> travels from the light source <NUM> to the wall of the cassette <NUM>, where it impinges on reflector <NUM>. The first portion of light <NUM> reflects off of the reflector <NUM> and travels to the detector <NUM>. The second portion of light <NUM> takes a different path to the detector <NUM>. The path taken by the second portion of light <NUM> excludes or bypasses the reflector <NUM>. The path length of light includes the physical distance traveled and any phase changes. In the embodiment shown, the paths taken by the portions of light <NUM> and <NUM> to the detector <NUM> in the absence of a pressure/vacuum being applied to the cassette <NUM> have different physical lengths. In addition, the first portion of light <NUM> undergoes a one hundred and eighty degree phase change because of the reflection off of the reflector <NUM>. The portions of light <NUM> and <NUM> are recombined/reunited at and/or near the detector <NUM>. Because the path lengths for the two portions of light <NUM> and <NUM> differ for various locations across the detector <NUM>, an interference pattern (not shown in <FIG>) is generated when the beams are combined. The spacing of the bright and dark fringes in the interference pattern depends upon the wavelength of light used. Using the detector <NUM> the locations of the bright and dark fringes of the interference pattern can be determined.

The bright and dark fringes of the interference pattern may be at particular locations when the cassette <NUM> is not under a vacuum or excess pressure. Stated differently, the interference pattern may be known for the case where the interior of the cassette <NUM> is at ambient pressure. Ambient pressure is the pressure of the environment surrounding the console <NUM>. When the vacuum source is activated, the interior of the cassette <NUM> is at a nonambient pressure (i.e. under vacuum in this scenario). Because the interior pressure of the cassette <NUM> is less than the ambient pressure, the wall(s) of the cassette may bend inward. Thus, the wall facing the interferometric pressure sensing system <NUM> may deflect. This deflection changes the position and, in some embodiments, shape of the reflector <NUM>. This deflection also changes the physical path length for the first portion of light <NUM> by an amount proportional to the deflection. As a result, the pattern of fringes changes. For example, the fringes may shift location. This shift in location is based both on the wavelength of light used and the size of the deflection. In general, the shift is proportional to the deflection and inversely proportional to the wavelength of the light in the portions <NUM> and <NUM>. Thus, shorter wavelength light yields a higher sensitivity in detection of the deflection.

Because the detector <NUM> can determine the locations of the fringes, the shift in the interference pattern may also be measured using the detector <NUM>. Using the measured shift, the deflection in the wall of the cassette <NUM> may be determined. Based on known properties of the walls of the cassette and/or a previous calibration, the internal cassette pressure causing this deflection may be ascertained. The calibrations may be made prior to use in surgery using an internal pressure sensor (not shown) in the cassette <NUM>. Alternatively, another method of calibration may be used. In certain embodiments, system-specific calibration data correlating fringe shift values with internal cassette pressure and/or cassette wall deflection values may be stored in memory (e.g., a memory of detection unit <NUM>) and used by one or more processors (e.g., a processor of detection unit <NUM>) to determine pressure values based on the interference pattern associated with the received light beam.

In some embodiments, the internal pressure of cassette <NUM> may be calculated by the detection unit <NUM> based on the shift in the interference pattern and calibration. For example, detector <NUM> may receive the recombined light beam and generate a signal indicating the location of bright and/or dark fringes of the interference pattern. Detection unit <NUM> may include hardware (e.g., one or more processor(s) and memory) and/or software configured to receive the signal from detector <NUM>. In a calibration phase, the detector <NUM> may send a signal to a processor of detection unit <NUM> indicating the location of fringes when the cassette is in various pressurized states, including a non-pressurized state (e.g., before a surgical procedure begins). Detection unit <NUM> may store this calibration fringe location information in memory. During a procedure, the detector <NUM> may send signals to detection unit <NUM> indicating the location of fringes as the cassette is in use during the procedure. As explained above, the location of the fringes will shift due to deflection in the wall of the cassette <NUM>, which alters the light beam reflected by reflector <NUM>. Accordingly, the processor of detection unit <NUM> may analyze the received signals indicating fringe location to determine cassette pressure. For example, the processor may compare signals received at different times (e.g., during a procedure) to calculate or determine a fringe shift. Based on the fringe shift, the processor of detection unit <NUM> may determine internal cassette pressure and/or the deflection in the cassette wall using data stored in memory that correlates fringe shift values with internal cassette pressure and/or deflection values. In some embodiments, the detection unit <NUM> includes a digital signal processor (DSP) used in processing the signal from the interferometric pressure sensing system <NUM>. In other embodiments, the internal pressure of the cassette <NUM> may be determined using a block (not shown) within the interferometric pressure sensing system <NUM>. A processor of detection unit <NUM> may then output a signal indicating the determined internal cassette pressure so that other components of system <NUM> may respond as appropriate by, for example, increasing or decreasing pressure in the eye to maintain a target pressure.

Thus, using the interferometric pressure sensing system <NUM>, the internal pressure of the cassette <NUM> may be determined. Because interferometry is used, the interferometric pressure sensing system <NUM> may more accurately determine pressure than, for example, the reflection method described above. The sensitivity of the interferometric pressure sensing system may be set using the wavelength of light from the light source. A lower wavelength light source <NUM> may be used to obtain a higher sensitivity measurement. Thus, the interferometric pressure sensing system <NUM> may be relatively easily tuned at the design phase. Because the interferometric pressure sensing system <NUM> is external to the cassette <NUM>, the pressure measurement is non-invasive. There is essentially no risk of the biological material removed from the patient contacting the interferometric pressure sensing system <NUM>. Thus, the interferometric pressure sensing system <NUM> may be less expensive and less likely to fail. Although the reflector <NUM> is added to the cassette <NUM>, the reflector <NUM> is relatively inexpensive. Not only may the internal pressure of the cassette <NUM> be more accurately measured, but the cost may also be reduced. Further, the interferometer used in the interferometric pressure sensing system <NUM> may be small. As a result, the interferometric pressure sensing system <NUM> may be relatively compact.

<FIG> depict another exemplary embodiment of a surgical system <NUM>' that measures pressure using an interferometric pressure sensing system. <FIG> are not to scale and for explanatory purposes only. Thus, a particular surgical system is not intended to be shown. <FIG> depicts the surgical system <NUM>' when the cassette <NUM>' is at ambient (zero applied) pressure. <FIG> depicts the surgical system <NUM>' when the cassette is under vacuum (less than ambient internal pressure). <FIG> depicts the surgical system <NUM>' when the cassette <NUM>' is under pressure (greater than ambient internal pressure). In general, a cassette is either placed under pressure or under vacuum, not both. However, both conditions are shown for the same cassette in order to explain operation of the surgical system <NUM>'.

The surgical system <NUM>' is analogous to the surgical system <NUM>. Analogous components have similar labels. The surgical system <NUM>' includes a console (not explicitly labeled), a cassette <NUM>' and an interferometric pressure sensing system <NUM>' analogous to components <NUM>, <NUM> and <NUM>, respectively. The pressure/vacuum source <NUM>' of the console is shown. The cassette <NUM>' may reside in the receptacle of the console. The port <NUM> of the cassette and analogous features are not shown.

The cassette <NUM>' is used to isolate the pressure/vacuum source <NUM>' from the biological material. The cassette <NUM>' includes the port <NUM> coupled with the pressure/vacuum source <NUM>' and the reflector <NUM>. In this embodiment, the reflector <NUM> is integrated into the wall of the cassette <NUM>'. In addition, the cassette <NUM>' includes an internal pressure sensor <NUM>. The internal pressure sensor <NUM> is used in calibrating the cassette <NUM>'. Consequently, the internal pressure sensor <NUM> may not be used during surgery.

The interferometric pressure sensing system <NUM>' is coupled with the console and takes the form of a Michelson interferometer. In other embodiments another interferometer might be used. The interferometric pressure sensing system <NUM>' includes a laser light source <NUM>', a detector <NUM>', an optional optical isolator <NUM>, additional reflector <NUM>, beam splitter <NUM> and optional filter <NUM>. The optical isolator <NUM> may be used to prevent reflected light from reaching the laser <NUM>'. The beam splitter <NUM> divides the light from the laser <NUM>' into two portions. The beam splitter <NUM> is also used in recombining the light in the embodiment shown. The beam splitter <NUM> may be a partially silvered mirror. The detector <NUM>' is a linear detector array. The filter <NUM> may be used to filter the signal from the detector <NUM>'. The filter <NUM> may be a low pass filter. For example, the filter <NUM> may pass signals having a frequency less than one hundred Hertz. In some such embodiments, the filter <NUM> may pass signals having a frequency of less than sixty Hz. Other threshold frequencies may be used to define the pass band for the filter <NUM>. For example, a band pass or other mechanism for reducing noise may be used. In other embodiments, another component such as a DSP might be used to process the signal from the detector <NUM>' in place of the filter <NUM>.

Light from the laser <NUM>' passes through the isolator <NUM> and strikes the beam splitter <NUM>. A first portion of the light is transmitted and refracted by the beam splitter <NUM> and reaches the reflector <NUM>. The reflector <NUM> reflects the first portion of the light back to the beam splitter <NUM>. Because the beam splitter <NUM> is a partially silvered mirror, this portion of light is also reflected down to the linear detector array <NUM>. A second portion of the light is reflected by the beam splitter <NUM> to the additional reflector <NUM>. This second portion of light is reflected back from the reflector <NUM> to the beam splitter <NUM>. The second portion of light is also transmitted by the beam splitter <NUM> to the linear detector array <NUM>'. The two portions of light are recombined, resulting in an interference pattern <NUM> at the linear detector array <NUM>'.

In this example, he two portions of light have traveled different physical paths. Both portions of light have undergone two reflections, each of which would alter the phase by one hundred and eighty degrees. The first portion is first reflected off of the reflector <NUM> and then off of the beam splitter <NUM>. The second portion is first reflected off of the beam splitter <NUM> and then off of the reflector <NUM>. The phase difference between the two portions that are recombined at the linear detector array <NUM> is due to the difference in physical path lengths. In other embodiments, any phase difference may be due partly to a difference in physical path lengths and partly to phase inversion(s) at reflection(s). As can be seen in <FIG>, the interference pattern <NUM> is formed for the cassette <NUM>' at the ambient internal pressure.

<FIG> depicts the system <NUM>' when the vacuum source <NUM>" provides a vacuum. Such a vacuum is typically measured in millimeters of mercury. For example, a vacuum of six hundred or seven hundred millimeters of mercury might be applied. In such cases, the internal pressure of the cassette <NUM>' is six hundred or seven hundred millimeters of mercury less than the ambient pressure. Because the internal pressure of the cassette <NUM>' is less than the ambient pressure, the wall of the cassette <NUM>' undergoes a deflection analogous to that shown in <FIG>. The reflector <NUM>' also undergoes a deflection. This deflection increases the distance between the beam splitter <NUM> and the reflector <NUM>' by the deflection, d1. The resulting increase in the distance traveled by the first portion of light being reflected by the reflector <NUM>' is approximately twice the deflection. Thus, the physical path length is increased by approximately twice the deflection for this portion of light. However, the path length has not been changed for the second portion of light reflecting off of the reflector <NUM>. As a result, the interference pattern <NUM>' shifts by a distance s1. If the vacuum source <NUM>" applies the vacuum during calibration, then the internal pressure sensor <NUM> is used to measure the internal pressure and calibrate the shift s1 to the deflection d1 and to the internal pressure. Such data may be stored in memory of detection unit <NUM>, as noted above. If the vacuum source <NUM>" provides the vacuum in order to apply suction to a patient's eye via an aspiration line (not shown), the sensor <NUM> is not used. Instead, the calibration previously obtained and the measured shift s1 and deflection d1 are used to ascertain the internal pressure of the cassette <NUM>'.

<FIG> depicts the system <NUM>' when the vacuum/pressure source <NUM>‴ provides a positive pressure to the cassette <NUM>'. For example, a pressure of eighty psi or more might be applied in some embodiments. Because the internal pressure of the cassette <NUM>' is greater than the ambient pressure, the wall of the cassette <NUM>' undergoes a deflection analogous to that shown in <FIG>. The reflector <NUM>" also undergoes a deflection. This deflection decreases the distance between the beam splitter <NUM> and the reflector <NUM>" by the deflection, d2. The resulting decrease in the distance traveled by the first portion of light being reflected by the reflector <NUM>" is approximately twice the deflection. However, the path length has not been changed for the second portion of light reflecting off of the reflector <NUM>. As a result, the interference pattern <NUM>" shifts by a distance s2. In the embodiment shown, the shift s2 is in a different direction and has a different magnitude than the shift s1. Other shifts are possible. If the vacuum/pressure source <NUM>‴ applies the pressure during calibration, then the internal pressure sensor <NUM> is used to measure the internal pressure and calibrate the shift s2 to the deflection d2 and to the internal pressure. Such data may be stored in memory of detection unit <NUM>, as noted above. If the vacuum source <NUM>‴ provides the pressure in order to supply fluid to a patient's eye via an irrigation line (not shown), the sensor <NUM> is not used. Instead, the calibration previously obtained, shift s2 and deflection d2 are used to measure the internal pressure of the cassette <NUM>'.

The system <NUM>' shares the benefits of the system <NUM>. Using the interferometric pressure sensing system <NUM>', the internal pressure of the cassette <NUM>' may be determined (e.g., by a processor and memory of detection unit <NUM> communicatively coupled to system <NUM>'). The interferometric pressure sensing system <NUM>' may be more accurate because interferometry is used. The interferometric pressure sensing system <NUM>' is external to the cassette <NUM>'. Thus, there is little to no risk of the biological material removed from the patient contacting the interferometric pressure sensing system <NUM>'. The addition to the disposable cassette <NUM>', the reflector <NUM>/<NUM>'/<NUM>", is relatively inexpensive. Thus, not only may the internal pressure of the cassette <NUM> be more accurately measured, but the cost may also be reduced. Further, because the interferometer used in the interferometric pressure sensing system <NUM>' may be small, the interferometric pressure sensing system <NUM> may be relatively compact.

<FIG> is an exemplary embodiment of a method <NUM> for providing a surgical system such as the surgical system(s) <NUM> and/or <NUM>'. For simplicity, some steps may be omitted, interleaved, and/or combined. The method <NUM> is also described in the context of the surgical system <NUM>. However, the method <NUM> may be used to form the surgical system <NUM>' and/or an analogous surgical system.

The cassette <NUM> including a reflector <NUM> is provided, via step <NUM>. Step <NUM> may include forming the cassette <NUM> and attaching the reflector <NUM>. Alternatively, the reflector <NUM> might be integrated into the wall of the cassette. In other embodiments, some or all of the wall of the cassette may be formed by the reflector <NUM>. In certain examples, some or all of the wall of the cassette may be coated with a reflective material.

The interferometric pressure sensing system <NUM> is provided and coupled with the console <NUM>, via step <NUM>. Step <NUM> may include forming the interferometric pressure sensing system <NUM> as part of the console <NUM>. In other embodiments, a separate interferometric sensing system <NUM> may be provided and connected to the console <NUM> via fiber optic cables, wiring, or other means. Components of the disclosed systems such as light source <NUM>, reflector <NUM>, beam splitter <NUM>, reflector <NUM>, and detector <NUM> are optically aligned. Using the method <NUM>, the surgical system <NUM> and/or <NUM>' may be fabricated. Thus, the benefits of one or more of the surgical systems <NUM> and/or <NUM>' may be achieved.

<FIG> is a flow chart depicting an exemplary embodiment of a method <NUM> for measuring an internal cassette pressure using a deflection in the wall of the cassette during ophthalmic surgery. For simplicity, some steps may be omitted, interleaved, performed in another order and/or combined. The method <NUM> may include executing instructions on one or more processors of system <NUM> configured to execute software instructions stored in memory. Further, the method <NUM> is described in the context of ophthalmic surgery using the surgical system <NUM>. However, the method <NUM> may be extended to other types of surgery.

The method commences after surgery has started. Thus, the surgeon has made incision(s) in the eye of the patient, performed other required tasks, and inserted the aspiration and/or irrigation line(s) in the eye of the patient. The interferometric pressure sensing system <NUM> has also been calibrated, for example using an internal sensor. The pressure in the cassette <NUM> may be greater than ambient if the cassette <NUM> is used to provide fluid to the patient's eye. The pressure in the cassette <NUM> may be less than ambient if the cassette <NUM> is used to extract material from the eye.

Light is provided from the light source <NUM>, at step <NUM>. Step <NUM> may include activating the laser <NUM>. The laser <NUM> may be controlled to be powered on and off intermittently power or may be simply powered on during use. Step <NUM> may also include allowing the light to pass through an isolator, such as the optical isolator <NUM>.

The light from the light source is split into two portions, at step <NUM>. Step <NUM> may be carried out by passing the light through a beam splitter such as the splitter <NUM>. Because of the configuration of the interferometric pressure sensing system <NUM>, the first portion of light is reflected off of the reflector <NUM>, while the second portion of light bypasses the reflector <NUM>. In some embodiments, the second portion of light is reflected off of the second reflector <NUM>.

The light that has traversed different paths is recombined, at step <NUM>. Step <NUM> may simply include allowing the light to pass back through the beam splitter <NUM> in a manner analogous to that shown in <FIG>. Thus, an interference pattern is developed. There may be a shift in the interference pattern if the pressure within the cassette <NUM> differs from the ambient.

If present, a shift in the interference pattern is detected, at step <NUM>. Step <NUM> may include detecting the interference pattern using light detector <NUM> and a processor of detector unit <NUM>. In certain examples, signals indicating a detected interference pattern, fringe position, or shift in fringe position may be transmitted to and received by a processor. The processor may be configured to analyze the signals to determine whether any shift is present and, if so, the size and magnitude of the shift. The processor may further use determined shift data to determine an internal cassette pressure and/or wall deflection, and to output a signal to other components of system <NUM> indicating the determined pressure. Thus, step <NUM> may include not only obtaining a signal from the detector <NUM>, but also processing the signal, determining shift, pressure, and deflection, and generating an output signal indicating pressure and/or deflection. One or more aspects of step <NUM> may be performed using software executed by a processor of detection unit <NUM>. The signal may also be filtered, at step <NUM>. Step <NUM> may be performed using a low pass filter. Alternatively, a band pass filter may be used to synchronize detection of the shift with the intermittent laser pulses if the light source <NUM> is powered on and off in step <NUM>. In some embodiments, step <NUM> occurs before or is part of step <NUM>. Thus, detection of the shift may be isolated from vibrations due to the pump or other sources of noise.

Claim 1:
A surgical system (<NUM>) comprising:
a cassette (<NUM>) for exchanging material with a patient, the cassette including a wall, a reflector (<NUM>) and an internal pressure sensor (<NUM>), the wall configured to undergo a deflection in response to a nonambient internal cassette pressure;
a console (<NUM>) coupled with the cassette; and
an interferometric pressure sensing system (<NUM>) coupled with the console, the interferometric pressure sensing system including a light source (<NUM>) and a detector (<NUM>), the light source providing a first portion of light (<NUM>) that is reflected off of the reflector (<NUM>) and a second portion of light (<NUM>) bypassing the reflector, the first portion and the second portion recombining to form an interference pattern (<NUM>), the deflection corresponding to a shift (S1) in the interference pattern (<NUM>) detectable by the detector (<NUM>);
wherein the internal pressure sensor (<NUM>) is configured to be used to measure an internal pressure of the cassette (<NUM>) and calibrate the shift (S1) in the interference pattern (<NUM>) to the deflection and to the internal pressure.