System and method for non-invasive measurement of cassette pressure

Abstract

To provide a surgical system including a cassette, a console and an interferometric pressure sensing system coupled with the console.SOLUTION: A method and a 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.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to ophthalmic surgical systems and methods. More particularly, the present disclosure relates to techniques for measuring cassette pressure in a surgical system.

Background Art

[0002] Ophthalmic surgery often involves removing fluid and / or tissue from the eye and replacing the removed substance with a fluid such as balanced salt solution (BSS). To remove the substance, a cannula connected to a suction line is inserted into an incision in the eye. The suction line is coupled to a console that includes an electronic circuit, a control system, a vacuum source such as a peristaltic pump, and a fluid source. The vacuum source provides a vacuum to the suction line. The vacuum in the suction line causes the substance to flow from the eye through the suction line. To maintain intraocular pressure, another cannula connected to a wash line or an infusion line is inserted into another incision in the eye. The wash line is connected to the fluid source of the console. The fluid source can be a reservoir of BSS that can be pressurized to a pressure higher than ambient pressure. When the fluid source is pressurized, fluid flow is forced out of the fluid source, through the wash line, and into the eye.

[0003] During such surgery, it is desirable to separate the biological substance removed from the eye from the vacuum pump. A cassette is used for this purpose. The cassette is typically fitted into a receptacle within the console. A tube from the suction line is connected to a port of the cassette. The cassette is connected to the vacuum source via another port. The vacuum source applies a vacuum to the cassette, and the cassette provides the vacuum to the suction line. The suction in the suction line causes the biological substance to flow from the eye into the cassette, where the biological substance is stored. Thus, the biological substance is separated from the vacuum pump. To provide fluid to the eye, another cassette coupled to a pressure source or a fluid source and the wash line can be used in a similar manner.

[0004] In use, a pressure sensor can be used to monitor the pressure within the cassette. For example, a rubber membrane can flex in response to the internal pressure of the cassette. This deflection can bring the membrane into contact with a contact sensor. Thus, the pressure can be determined. Alternatively, the sensor can provide light that is reflected from the membrane at an oblique angle. The reflected light is provided to the sensor. The change in the position of the light corresponds to the change in the internal pressure.

[0005] Such mechanisms for measuring the internal pressure of cassette functions can have drawbacks. For example, using reflected light may not provide sufficient sensitivity to the internal pressure. Further, the flexible membrane increases the cost of each disposable cassette. The internal pressure sensor can be affected by biological substances removed from the eye. Thus, such a sensor can malfunction. These sensors also increase the cost of the disposable cassette.

Summary of the Invention

Problems to be Solved by the Invention

[0006] Accordingly, what is needed is an improved mechanism for monitoring the internal pressure of a cassette in a surgical system.

Means for Solving the Problems

[0007] A method and system provide a surgical system that includes a cassette, a console, and an interferometric pressure sensing system coupled to the console. The cassette is for exchanging substances with a patient and includes a wall and a reflector. The wall undergoes deflection in response to non-ambient cassette internal pressure. The console is coupled to the cassette. The interferometric pressure sensing system is coupled to the console. The interferometric pressure sensing system includes a light source and a detector. The light source provides a first portion of light reflected by the reflector and a second portion of light that bypasses the reflector. The first and second portions of light are recombined to form an interference pattern. The deflection corresponds to a shift in the interference pattern detectable by the detector.

[0008] According to embodiments of the methods and systems disclosed herein, the internal pressure of the cassette can be measured more accurately, without the need to use a sensor inside the cassette and without the need for expensive add-ons to the cassette.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figures 3A-3B

Figure 3C

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0010] Exemplary embodiments relate to surgical systems such as consoles used in ophthalmic surgery. The following description is presented to enable one skilled 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 described herein, as well as the general principles and features, will be readily apparent. Exemplary embodiments are mainly described with respect to specific methods and systems provided in a particular implementation form. However, the methods and systems will also operate effectively in other implementation forms. Phrases such as "exemplary embodiments", "one embodiment", and "another embodiment" may refer to the same or different embodiments and multiple embodiments. Embodiments are described with respect to systems and / or devices having a particular embodiment. However, the systems and / or devices may include more or fewer components than those shown, and variations in the configuration and type of components may be made without departing from the scope of the invention. Exemplary embodiments are also described with respect to a particular method having specific steps. However, the methods and systems will also operate effectively in other methods having different and / or additional steps and steps in a different order that do not conform to the exemplary embodiments. Accordingly, the invention is not limited to the embodiments shown, but should follow the broadest scope consistent with the principles and features described herein.

[0011] The methods and systems are also described in the singular rather than the plural. For example, one cassette having one interferometric pressure sensing system is used and / or shown in some embodiments. Those skilled in the art will recognize that these singular terms include the plural. For example, multiple cassettes and / or multiple interferometric sensing systems may be used.

[0012] In certain embodiments, the system includes one or more processors and 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 processes described in the drawings and hereinafter. As used herein, a processor may include one or more microprocessors, a field programmable gate array (FPGA), a controller, or any other suitable computing device or resource, and the memory may take the form of volatile or non-volatile memory including, but not limited to, magnetic media, optical media, random access memory (RAM), read only memory (ROM), removable media, or any other suitable memory component. The memory may store instructions of programs and algorithms described herein for performing the functions described herein with respect to any such processor, memory, or component including processing capabilities when executed by the processor. Further, aspects of the methods and systems may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software aspects and hardware aspects. Further, aspects of the methods and systems may take the form of software components implemented on one or more computer-readable media having computer-readable program code executed by at least one processor and embodied therein.

[0013] The methods and systems provide a surgical system that includes a cassette, a console, and an interferometric pressure sensing system coupled to the console. The cassette is for exchanging substances with a patient and includes a wall and a reflector. The wall is deflected in response to a non-ambient cassette internal pressure. The console is coupled to the cassette. The interferometric pressure sensing system is coupled to the console. The interferometric pressure sensing system includes a light source and a detector. The light source provides a first portion of light reflected by the reflector and a second portion of light that bypasses the reflector. The first and second portions of light are recombined to form an interference pattern. The deflection corresponds to a shift in the interference pattern detectable by the detector.

[0014] FIG. 1 shows a perspective view of an exemplary embodiment of a surgical system 100 that can be used in ophthalmic surgery. FIG. 2 shows a part of the surgical system 100. Referring to FIGS. 1 and 2, the surgical system 100 includes a console 101, a cassette 110, and an interferometric pressure sensing system 120. FIGS. 1 and 2 are not drawn to scale and are for illustrative purposes only. Thus, the system 100 is not limited to a particular console 101, cassette 110, or interferometric sensing system 120. For example, although a particular position and geometry of the cassette 110 within the console 101 are shown in FIG. 1, the surgical system 100 is not limited to the shown position and geometry. For simplicity, not all parts of the console 101 are shown or described. The console 101 is coupled to the cassette 110 and the interferometric sensing system 120. In use, the console 101 is typically also coupled to a surgical handpiece (not shown). The surgical handpiece can include a suction line and / or a wash line connected to the console 101 via a tube (not shown) and an electronic circuit connected to and controlled by the console 101.

[0015] The console 101 includes a display 102, associated electronic circuitry (not explicitly shown or described), a vacuum / pressure source 104, a receptacle 106 for receiving a cassette 110, and a detection unit 140. In some embodiments, the console 101 may include both a vacuum source and a pressure source. In such embodiments, the vacuum source and the pressure source may be coupled to different cassettes that may be present in the same or different receptacles. However, for simplicity, the surgical system 100 is described with respect to one receptacle 106, one cassette 110, and one vacuum / pressure source 104. The vacuum / pressure source 104 is mainly described with respect to the vacuum source 104. Similar considerations apply to fluid / pressure sources. Although shown as part of the console 101 in FIG. 1, the detection unit 140 may be part of an interferometric pressure sensing system 120. The detection unit 140 is communicatively coupled to the interferometric pressure sensing system 120 and other components of the system 100. In certain embodiments, the detection unit 140 receives one or more signals (e.g., a signal indicating an interference pattern or a shift in the interference pattern generated by a detector 124) from the pressure sensing system 120 and may include one or more processors and memories configured to identify the cassette pressure based on the received signals based on stored data correlating a shift or change in the interference pattern to the cassette internal pressure and / or wall deflection as described herein.

[0016] The vacuum / pressure source 104 is coupled to the cassette 110 through the receptacle 110. The vacuum / pressure source 104 can be a vacuum source such as a vacuum pump. In such embodiments, the vacuum source 104 provides a negative pressure (vacuum) to the cassette 110, and the cassette 110 provides the vacuum to a suction line. In other embodiments, the vacuum / pressure source 104 can be a pressure source that provides a positive pressure to the cassette 110. The cassette 110 is coupled to a fluid source, and the fluid source provides fluid to a wash line under positive pressure. Alternatively, the vacuum / pressure source 104 can be a fluid source that can be disposed under positive pressure (a pressure greater than atmospheric pressure).

[0017] Cassette 110 is for exchanging substances with a patient. In the illustrated embodiment, cassette 110 receives tissue, fluid, and / or other biological substances from the patient's eye. In other embodiments, cassette 110 can be used to provide a fluid such as BSS to the patient's eye. The cassette includes a wall and an internal chamber (not explicitly shown in FIG. 1). Cassette 110 also includes a reflector 112 (not shown in FIG. 1) shown in FIG. 2. Reflector 112 can be a mirror or any other suitable reflector. Reflector 112 can be attached to the wall or integrated into the wall. Thus, in some embodiments, the wall itself can be reflective. In a particular example, the wall can be coated with or bonded to a reflective material. Cassette 110 is oriented such that reflector 112 faces interferometric detection system 120. In the illustrated embodiment, the normal to the surface of reflector 112 is orthogonal to interferometric detection system 120. Reflector 112 can be at an oblique angle to some or all of interferometric detection system 120 in other embodiments.

[0018] Ports 114 and 116 are also shown. Port 114 can be connected to a tube (not shown) and thus to a surgical handpiece. Port 116 is connected to vacuum source 104. Thus, vacuum is provided to cassette 110 through port 116 while suction is provided to a suction line through port 114. Biological substances from the patient's eye are received in cassette 110 through port 114. This biological substance remains within cassette 110. Thus, cassette 110 separates vacuum source 104 from the biological substance.

[0019] The interferometric pressure detection system 120 is coupled to the console 101. In certain examples, the interferometric pressure detection system 120 can be considered to be incorporated into the console 101. Thus, the interferometric pressure detection system 120 coupled to the console 101 includes some or all of the components of the interferometric pressure detection system that are part of the console 101, but is not limited thereto. In other embodiments, some or all of the components of the interferometric pressure detection system need not be incorporated into the console 101. In such embodiments, the light used can be transmitted to an appropriate location, for example, via an optical fiber cable. In such embodiments, also, control signals and data signals can be transmitted between the console 101 and the interferometric pressure detection system 120 via wiring.

[0020] The interferometric pressure detection system 120 includes a light source 122 and a detector 124. The detector 124 can be a linear or area detector array. In certain embodiments, the detector 124 can include any suitable photodetector (e.g., CMOS, CCD, etc.). In some embodiments, the light source 122 can include a laser. In particular, multiple light sources can be used if the light generated is in phase and of the same wavelength. However, generally there is one light source 122. The interferometric pressure detection system 120 divides the light into a first portion and a second portion. Generally, a beam splitter or similar component is used to divide the light from the light source 122 into multiple portions. In FIG. 2, these portions of the light are shown as two separate beams 132 and 134 emitted from the light source 122. However, one of ordinary skill in the art will recognize that the portions of the light actually correspond to multiple beams having some physical width and slightly different trajectories.

[0021] The first portion 132 of light travels from the light source 122 to the wall of the cassette 110 and impinges on the reflector 112 at the wall. The first portion 132 of light is reflected by the reflector 112 and travels to the detector 124. The second portion 134 of light follows a different path to reach the detector 124. The path followed by the second portion 134 of light excludes or bypasses the reflector 112. The optical path length includes the physical distance traveled and any phase changes. In the illustrated embodiment, the paths followed by the portions 132 and 134 of light to reach the detector 124 have different physical lengths when no pressure / vacuum is applied to the cassette 110. Additionally, the first portion 132 of light undergoes a 180-degree phase change due to reflection from the reflector 112. The portions 132 and 134 of light recombine / re-integrate at or near the detector 124. Since the path lengths of the two portions 132 and 134 of light are different at various positions across the detector 124, an interference pattern (not shown in FIGS. 1 and 2) is generated when the beams are combined. The spacing between the bright and dark fringes in the interference pattern depends on the wavelength of the light used. The detector 124 can be used to identify the positions of the bright and dark fringes of the interference pattern.

[0022] The bright and dark fringes of the interference pattern can be in specific positions when the cassette 110 is not under vacuum pressure or excessive pressure. In other words, the interference pattern can be known when the interior of the cassette 110 is at ambient pressure. Ambient pressure is the pressure of the surrounding environment of the console 101. When the vacuum source is activated, the interior of the cassette 110 is at non-ambient pressure (i.e., under vacuum in this situation). Since the internal pressure of the cassette 110 is less than ambient pressure, the walls of the cassette can curve inward. Thus, the wall facing the interferometric pressure sensing system 120 can deflect. This deflection changes the position and in some embodiments the shape of the reflector 112. This deflection also changes the physical path length of the first portion 132 of light by an amount proportional to the deflection. As a result, the pattern of the fringes changes. For example, the fringes can shift in position. This shift in position is based on both the wavelength of the light used and the size of the deflection. Generally, the shift is proportional to the deflection and inversely proportional to the wavelength of the light in portions 132 and 134. Thus, the shorter the wavelength of the light, the higher the sensitivity to detect the deflection.

[0023] Since the detector 124 can identify the position of the stripes, the shift of the interference pattern can also be measured using the detector 124. The measured shift can be used to identify the deflection of the wall of the cassette 110. Based on the known characteristics of the wall of the cassette and / or previous calibrations, the internal pressure of the cassette that caused this deflection can be identified. The calibration can be performed prior to surgical use using an internal pressure sensor (not shown) within the cassette 110. Alternatively, another calibration method can be used. In certain embodiments, system-specific calibration data correlating stripe shift values to internal cassette pressure and / or cassette wall deflection values is stored in a memory (e.g., the memory of the detection unit 140) and used by one or more processors (e.g., the processor of the detection unit 140) to identify pressure values based on the interference pattern associated with the received light beam.

[0024] In some embodiments, the internal pressure of the cassette 110 can be calculated by the detection unit 140 based on the shift and calibration of the interference pattern. For example, the detector 124 can receive the recombined light beam and generate a signal indicating the position of the bright and / or dark fringes of the interference pattern. The detection unit 140 can include hardware (e.g., one or more processors and memories) and / or software configured to receive the signal from the detector 124. In the calibration phase, the detector 124 can transmit to the processor of the detection unit 140 signals indicating the position of the fringes when the cassette is in various pressurized states, including a non-pressurized state (e.g., before the surgical procedure begins). The detection unit 140 can store this calibration fringe position information in memory. During the procedure, the detector 124 can transmit to the detection unit 140 a signal indicating the position of the fringes when the cassette is being used during the procedure. As described above, the position of the fringes shifts due to the deflection of the walls of the cassette 110 that changes the light beam reflected by the reflector 112. Thus, the processor of the detection unit 140 can analyze the received signal indicating the position of the fringes to identify the cassette pressure. For example, the processor can compare the signals received at different times (e.g., during the procedure) to calculate or identify the fringe shift. Based on the fringe shift, the processor of the detection unit 140 can use the data stored in memory that correlates the fringe shift value to the internal cassette pressure and / or deflection value to identify the internal cassette pressure and / or the deflection of the cassette walls. In some embodiments, the detection unit 140 includes a digital signal processor (DSP) used for processing the signals from the interferometer-based pressure sensing system 120. In other embodiments, the internal pressure of the cassette 110 can be identified using a block (not shown) within the interferometer-based pressure sensing system 120. Next, the processor of the detection unit 140 can output a signal indicating the identified internal cassette pressure, and thus, other components of the system 100 can respond appropriately, e.g., by increasing or decreasing the intraocular pressure to maintain the target pressure.

[0025] Accordingly, the internal pressure of the cassette 110 can be identified using the interferometric pressure detection system 120. Since the interference method is used, the interferometric pressure detection system 120 can identify the pressure more accurately than, for example, the reflection method described above. The sensitivity of the interferometric pressure detection system can be set using the wavelength of the light from the light source. To obtain a more sensitive measurement, a light source 122 with a lower wavelength can be used. Accordingly, the interferometric pressure detection system 120 can be adjusted relatively easily in the design phase. Since the interferometric pressure detection system 120 is outside the cassette 110, the pressure measurement is non-invasive. Basically, there is no risk that the biological material removed from the patient comes into contact with the interferometric pressure detection system 120. Accordingly, the interferometric pressure detection system 120 can be less expensive and can have a lower probability of failure. Although the reflector 112 is added to the cassette 110, the reflector 112 is relatively inexpensive. It is possible not only to measure the internal pressure of the cassette 110 more accurately but also to reduce the cost. Furthermore, the interferometer used in the interferometric pressure detection system 120 can be small. As a result, the interferometric pressure detection system 120 can be relatively compact.

[0026] Figures 3A - 3C show another exemplary embodiment of the surgical system 100' that measures pressure using an interferometric pressure detection system. Figures 3A - 3C are not drawn to scale and are for illustrative purposes only. Accordingly, no particular surgical system is shown. Figure 3A shows the surgical system 100' when the cassette 110' is at ambient (zero applied) pressure. Figure 3B shows the surgical system 100' when the cassette is under vacuum (less than ambient internal pressure). Figure 3C shows the surgical system 100' when the cassette 110' is under pressure (greater than ambient internal pressure). Generally, the cassette is either placed under pressure, under vacuum, or neither. However, to explain the operation of the surgical system 100', the same cassette in both situations is shown.

[0027] Surgical system 100’ is similar to surgical system 100. Similar components have similar reference numerals. Surgical system 100’ includes a console (not explicitly shown), cassette 110’, and interferometric pressure sensing system 120’ that are similar to components 101, 110, and 120, respectively. The pressure / vacuum source 104’ of the console is shown. Cassette 110’ may be present within a receptacle of the console. Ports 114 of the cassette and similar features are not shown.

[0028] Cassette 110’ is used to isolate the pressure / vacuum source 104’ from biological substances. Cassette 110’ includes a port 116 and a reflector 112 coupled to the pressure / vacuum source 104’. In this embodiment, reflector 112 is integrated into the wall of cassette 110’. Additionally, cassette 110’ includes an optional internal pressure sensor 118. Internal pressure sensor 118 is used for calibration of cassette 110’. Thus, internal pressure sensor 118 may not be used during surgery.

[0029] The interferometric pressure detection system 120’ is coupled to a console and can take the form of a Michelson interferometer. In other embodiments, other interferometers can be used. The interferometric pressure detection system 120’ includes a laser light source 122’, a detector 124’, an optional optical isolator 123, an additional reflector 126, a beam splitter 128, and an optional filter 129. The optical isolator 123 can be used to prevent reflected light from reaching the laser 122’. The beam splitter 128 splits the light from the laser 122’ into two parts. The beam splitter 128 is also used for light recombination in the illustrated embodiment. The beam splitter 128 can be a partially silver-coated mirror. The detector 124’ is a linear detector array. The filter 129 can be used to filter the signal from the detector 124’. The filter 129 can be a low-pass filter. For example, the filter 129 can pass signals having frequencies less than 100 Hz. In some such embodiments, the filter 129 can pass signals having frequencies less than 60 Hz. Other threshold frequencies can be used to define the passband of the filter 129. For example, other mechanisms such as band-pass or noise reduction can be used. In other embodiments, other components such as a DSP can be used instead of the filter 129 to process the signal from the detector 124’.

[0030] The light from the laser 124’ passes through the isolator 123 and impinges on the beam splitter 128. The first part of the light is transmitted and refracted by the beam splitter 128 and reaches the reflector 112. The reflector 112 reflects the first part of the light back to the beam splitter 128. Since the beam splitter 128 is a partially silver-coated mirror, this part of the light is also reflected to the lower linear detector array 124. The second part of the light is reflected by the beam splitter 128 to the additional reflector 126. This second part of the light is reflected from the reflector 126 back to the beam splitter 128. The second part of the light is also transmitted by the beam splitter 128 and reaches the linear detector array 124’. The two parts of the light are recombined to produce an interference pattern 135 on the linear detector array 124’.

[0031] In this example, the two portions of light followed different physical paths. Both portions of light underwent two reflections, each reflection changing the phase by 180 degrees. The first portion was first reflected by reflector 112 and then by beam splitter 128. The second portion was first reflected by beam splitter 128 and then by reflector 126. The phase difference between the two portions recombined at linear detector array 124 was due to the difference in physical path lengths. In other embodiments, any phase difference can be due in part to the difference in physical path lengths and in part to a phase inversion in the reflection. As can be seen in FIG. 3A, an interference pattern 135 is formed when cassette 110’ is at ambient internal pressure.

[0032] FIG. 3B shows system 100’ when vacuum source 104’’ provides a vacuum. Such a vacuum is typically measured in millimeters of mercury column. For example, a vacuum of 600 mmHg or 700 mmHg can be applied. In such a case, the internal pressure of cassette 110’ is 600 mmHg or 700 mmHg lower than the ambient pressure. Since the internal pressure of cassette 110’ is less than the ambient pressure, the walls of cassette 110’ undergo deflection as shown in FIG. 3B. Reflector 112’ also undergoes deflection. This deflection increases the distance between beam splitter 128 and reflector 112’ by deflection d1. As a result, the increase in the distance traveled by the first portion of light reflected by reflector 112’ is approximately twice the deflection. Thus, the physical path length increases by approximately twice the deflection of this portion of the light. However, for the second portion of light reflected by reflector 126, the path length does not change. As a result, interference pattern 135’ shifts by distance s1. During calibration, when vacuum source 104’’ applies a vacuum, internal pressure sensor 118 can be used to measure the internal pressure and calibrate shift s1 to deflection d1 and the internal pressure. Such data can be stored in the memory of detection unit 140 as described above. When vacuum source 104’’ provides a vacuum to apply suction to the patient's eye via a suction line (not shown), sensor 118 is not used. Instead, the previously obtained calibration along with the measured shift s1 and deflection d1 are used to determine the internal pressure of cassette 110’.

[0033] FIG. 3C shows system 100' when vacuum / pressure source 104''' provides positive pressure to cassette 110'. In some embodiments, for example, a pressure of 80 psi or more can be applied. Since the internal pressure of cassette 110' is higher than the ambient pressure, the walls of cassette 110' are deflected as shown in FIG. 3C. Reflector 112'' is also deflected. This deflection reduces the distance between beam splitter 128 and reflector 112'' by deflection d2. As a result, the reduction in the distance traveled by the first portion of the light reflected by reflector 112'' is approximately twice the deflection. However, for the second portion of the light reflected by reflector 126, the path length does not change. As a result, interference pattern 135'' shifts by distance s2. In the illustrated embodiment, shift s2 is in a different direction and has a different magnitude than shift s1. Other shifts are possible. During calibration, when vacuum / pressure source 104''' applies pressure, internal pressure sensor 118 can be used to measure the internal pressure and calibrate shift s2 to deflection d2 and the internal pressure. Such data can be stored in the memory of detection unit 140 as described above. When vacuum source 104''' provides pressure to supply fluid to the patient's eye via a cleaning line (not shown), sensor 118 is not used. Instead, the previously obtained calibration, shift s2, and deflection d2 are used to measure the internal pressure of cassette 110'.

[0034] System 100' shares the advantages of System 100. The internal pressure of cassette 110' can be identified using an interferometric pressure detection system 120' (e.g., by the processor and memory of detection unit 140 communicatively coupled to system 120'). The interferometric pressure detection system 120' can be more accurate because the interference method is used. The interferometric pressure detection system 120' is external to cassette 110'. Thus, the risk that biological substances removed from the patient contact the interferometric pressure detection system 120' is minimal, if any. The reflectors 112 / 112' / 112'', which are add-ons to the disposable cassette 110', are relatively inexpensive. Thus, not only can the internal pressure of cassette 110 be measured more accurately, but the cost can also be reduced. Further, since the interferometer used in the interferometric pressure detection system 120' can be small, the interferometric pressure detection system 120 can be relatively compact.

[0035] Figure 4 is an exemplary embodiment of a method 200 for providing a surgical system such as surgical system 100 and / or 100'. For simplicity, some steps may be omitted, interleaved, and / or combined. Method 200 is also described with respect to surgical system 100. However, method 200 can be used to form surgical system 100' and / or similar surgical systems.

[0036] A cassette 110 including a reflector 112 is provided via step 202. Step 202 can include forming the cassette 110 and attaching the reflector 112. Alternatively, the reflector 112 can be integrated into the wall of the cassette. In other embodiments, some or all of the walls of the cassette can be formed by the reflector 112. In certain examples, some or all of the walls of the cassette can be coated with a reflective material.

[0037] The interferometric pressure sensing system 120 is provided via step 204 and coupled to the console 101. Step 204 may include forming the interferometric pressure sensing system 120 as part of the console 101. In other embodiments, a separate interferometric sensing system 120 may be provided and connected to the console 101 via an optical fiber cable, wiring, or other means. The components of the disclosed system, such as the light source 122, reflector 112, beam splitter 128, reflector 126, and detector 124, are optically aligned. The surgical system 100 and / or 100' may be fabricated using the method 200. Accordingly, one or more advantages of the surgical system 100 and / or 100' may be achieved.

[0038] FIG. 5 is a flowchart showing an exemplary embodiment of a method 210 for measuring the pressure inside a cassette using the deflection of the cassette wall during an ophthalmic surgery. For simplicity, some steps may be omitted, interleaved, executed in a different order, and / or combined. The method 210 may include executing instructions on one or more processors of a system 100 configured to execute software instructions stored in a memory. Further, the method 210 is described with respect to ophthalmic surgery using the surgical system 100. However, the method 210 may be extended to other types of surgeries.

[0039] The method starts before the surgery begins. Accordingly, the surgeon has incised the patient's eye, performed other required tasks, and inserted the suction line and / or the irrigation line into the patient's eye. The interferometric pressure sensing system 120 is also calibrated, for example, using an intraocular pressure sensor. If the cassette 110 is used to provide fluid to the patient's eye, the pressure inside the cassette 110 may be a value greater than the ambient. If the cassette 110 is used to extract substances from the eye, the pressure inside the cassette 110 may be less than the ambient.

[0040] In step 212, light is provided from light source 122. Step 212 may include activating laser 122. Laser 122 may be controlled to be intermittently powered on and off, or may simply be powered on during use. Step 212 may include passing the light through an isolator such as optical isolator 123.

[0041] In step 214, the light from the light source is split into two portions. Step 214 may be performed by passing the light through a beam splitter such as beam splitter 128. Due to the configuration of the interferometric pressure sensing system 120, the first portion of the light is reflected by reflector 112 while the second portion of the light bypasses reflector 112. In some embodiments, the second portion of the light is reflected by a second reflector 126.

[0042] In step 216, the light that has traveled different paths is recombined. Step 216 may simply include passing the light through beam splitter 128 as shown in FIGS. 3A - 3C. Thus, an interference pattern is generated. If the pressure within cassette 110 is different from the ambient pressure, the interference pattern may shift.

[0043] When there is a shift in the interference pattern, at step 218, the shift in the interference pattern is detected. Step 218 may include detecting the interference pattern using the photodetector 124 and the processor of the detection unit 140. In a particular example, a signal indicating the detected interference pattern, the position of the fringes, or the shift in the position of the fringes may be transmitted to and received by the processor. The processor may be configured to analyze the signal to determine whether any shift exists and, if so, to identify the size and magnitude of the shift. The processor may further use the identified shift data to identify the cassette internal pressure and / or wall deflection and output a signal indicating the identified pressure to other components of the system 100. Thus, step 218 may include not only acquiring the signal from the detector 124 but also processing the signal, identifying the shift, pressure, and deflection, and generating an output signal indicating the pressure and / or deflection. One or more aspects of step 218 may be performed using software executed by the processor of the detection unit 140. At step 220, the signal can also be filtered. Step 220 may be performed using a low-pass filter. Alternatively, at step 212, when the light source 122 is turned on and off, a band-pass filter may be used to synchronize the detection of the shift with the intermittent laser pulses. In some embodiments, step 220 is performed before step 218 or as part of step 218. Thus, the detection of the shift can be separated from vibrations caused by the pump or other noise sources.

[0044] Using method 210, the pressure within cassette 110 / 110’ can be non-invasively detected during surgical use. Thus, various advantages of surgical system 100 and / or 100’ can be achieved. A method and system for providing a surgical system capable of identifying cassette pressure by an interferometry method during ophthalmic surgery have been described. The method and system are described according to the illustrated exemplary embodiments, and those skilled in the art can readily recognize that there may be variations to the embodiments, and any variations are within the spirit and scope of the method and system. Thus, many modifications can be made by those skilled in the art without departing from the spirit and scope of the appended claims. According to aspect (1), a cassette for exchanging substances with a patient, comprising a wall and a reflector, the wall being configured to receive deflection in response to a non-ambient cassette internal pressure, a cassette, and a console coupled to the cassette, and an interferometric pressure sensing system coupled to the console, comprising a light source and a detector, the light source providing a first portion of light reflected by the reflector and a second portion of light bypassing the reflector, the first portion and the second portion recombining to form an interference pattern, the deflection corresponding to a shift in the interference pattern detectable by the detector, an interferometric pressure sensing system, and a surgical system comprising the same. According to aspect (2), the interference pattern results from a difference in the physical paths of the first portion of the light and the second portion of the light. According to aspect (3), the interferometric pressure sensing system includes a Michelson interferometer. According to aspect (4), the Michelson interferometer includes a beam splitter and an additional reflector, the light from the light source passing through the beam splitter to form the first portion and the second portion of the light, the additional reflector being coupled to a portion of the receptacle. According to aspect (5), further comprising a processor, the processor being receiving a signal related to the interference pattern from the detector, and calculating a shift in the interference pattern based on the received signal, and identifying a cassette pressure based on the calculated shift configured to perform. According to aspect (6), the light source and the detector are integrated into the console. According to aspect (7), the reflector is integrated into the wall of the cassette. According to aspect (8), the reflector is coupled to the wall of the cassette. According to aspect (9), the light source is a laser. According to aspect (10), the light source has a wavelength, and the shift in the interference pattern corresponds to twice the deflection divided by the wavelength. According to aspect (11), the non-ambient pressure is greater than the ambient pressure, and the deflection is such that the reflector is closer to the detector. According to aspect (12), the non-ambient pressure is less than the ambient pressure, and the deflection is such that the reflector is farther from the detector. According to aspect (13), the interferometric pressure detection system further includes a low-pass filter coupled to the detector, the low-pass filter being for transmitting a signal corresponding to the shift, and the low-pass filter having a passband below a threshold frequency. According to aspect (14), the console includes a receptacle configured to receive the cassette. According to aspect (15), an interferometric pressure detection system for a surgical cassette, a light source configured to provide a light beam, a beam splitter and, the beam splitter is configured to direct a first portion of the light beam towards a reflector in a wall of the surgical cassette, the wall being configured to deflect in response to a non-ambient cassette internal pressure, direct a second portion of the light beam to bypass the reflector on its way to a detection unit and, the detection unit includes a light sensor, a processor, and a memory, receive a recombined light beam including the first portion of the light beam reflected by the reflector and the second portion of the light beam bypassing the reflector, detect an interference pattern associated with the recombined light beam, analyze the detected interference pattern to identify a shift in the interference pattern, the shift corresponding to the deflection of the wall of the surgical cassette, and determine a cassette internal pressure based on the identified shift An interferometric pressure detection system configured to perform the above.

Claims

1. A cassette for exchanging substances with a patient, comprising a wall, a reflector, and an internal pressure sensor, wherein the wall is configured to receive deflection in response to non-ambient cassette internal pressure, the cassette, and a console coupled to the cassette, and an interferometric pressure sensing system coupled to the console, comprising a light source and a detector, wherein the light source provides a first portion of light reflected by the reflector and a second portion of light bypassing the reflector, and the first portion and the second portion recombine to form an interference pattern, and the deflection corresponds to a shift of the interference pattern detectable by the detector, the interferometric pressure sensing system, and comprising, wherein the internal pressure sensor measures the internal pressure of the cassette and is configured to convert the shift of the interference pattern into the deflection and the internal pressure, a surgical system.

2. The surgical system according to claim 1, wherein the non-ambient cassette internal pressure includes positive pressure or negative pressure.

3. The surgical system according to claim 1, wherein the interference pattern results from a difference in the physical paths of the first portion and the second portion of the light.

4. The surgical system according to claim 1, wherein the interferometric pressure sensing system includes a Michelson interferometer.

5. The Michelson interferometer includes a beam splitter and an additional reflector, the light from the light source passes through the beam splitter to form the first portion and the second portion of the light, and the additional reflector is coupled to a portion of the receptacle, the surgical system according to claim 4.

6. Further comprising a processor, the processor is configured to receive a signal related to the interference pattern from the detector, calculate a shift of the interference pattern based on the received signal, and identify the cassette pressure based on the calculated shift, the surgical system according to claim 1.

7. The surgical system according to claim 1, wherein the light source and the detector are integrated into the console.

8. The surgical system according to claim 1, wherein the reflector is integrated into the wall of the cassette.

9. The surgical system according to claim 1, wherein the reflector is coupled to the wall of the cassette.

10. The surgical system according to claim 1, wherein the light source is a laser.

11. The surgical system according to claim 1, wherein the light source has a wavelength, and the shift of the interference pattern corresponds to twice the deflection divided by the wavelength.

12. The surgical system according to claim 1, wherein the non-ambient cassette internal pressure is greater than the ambient pressure, and the deflection is such that the reflector is closer to the detector.

13. The surgical system according to claim 1, wherein the non-ambient cassette internal pressure is less than the ambient pressure, and the deflection is such that the reflector is farther from the detector.

14. The surgical system according to claim 1, wherein the interferometric pressure sensing system further includes a low-pass filter coupled to the detector, the low-pass filter is for transmitting a signal corresponding to the shift, and the low-pass filter has a passband below a threshold frequency.

15. The surgical system according to claim 1, wherein the console includes a receptacle configured to receive the cassette.

16. The light source of the interferometric pressure sensing system is configured to provide a light beam. The interferometric pressure sensing system includes a beam splitter. The beam splitter is configured to direct a first portion of the light beam toward the reflector at the wall of the cassette, and to direct a second portion of the light beam to bypass the reflector on the way to the detector and is configured to perform the above operations. The detector includes a light sensor, a processor, and a memory. receive a recombined light beam including the first portion of the light beam reflected by the reflector and the second portion of the light beam that bypassed the reflector, detect an interference pattern associated with the recombined light beam, analyze the detected interference pattern to identify a shift of the interference pattern, the shift corresponding to the deflection of the wall of the cassette, and identify the shift, and identify the internal pressure of the cassette based on the identified shift and is configured to perform the above operations, and is the surgical system according to claim 1.

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