INTRAOCULAR PRESSURE FLUCTUATION CANCELLATION

A phacoemulsification system, including a probe having an irrigation channel and an aspiration channel, and a distal end including a needle and a sleeve insertable into an eye. There is an irrigation pump pumping irrigation fluid via the irrigation channel into the eye, and an aspiration pump pumping aspiration fluid via the aspiration channel from the eye. A first pressure sensor is coupled with the irrigation fluid and provides a first signal of intraocular pressure (IOP) in the eye; a second pressure sensor is coupled with the aspiration fluid and provides a second signal of the IOP. A system processor receives the first and second signals, and responsively to at least one of the signals, identifies at least one frequency and an associated at least one phase of the IOP, and pumps at least one of the pumps at the identified frequency and in antiphase to the identified phase.

FIELD OF THE DISCLOSURE

This disclosure relates generally to ocular surgery, and specifically to changes in the intraocular pressure (IOP) that may occur during the surgery.

BACKGROUND

A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Phacoemulsification is a modern cataract surgery method in which the eye's internal lens is emulsified with an ultrasonic handpiece and aspirated from the eye. The aspirated fluids may be replaced by irrigation of the eye with a balanced salt solution to maintain the intraocular pressure (IOP) of the eye. Even so, during the surgery the IOP typically varies.

DESCRIPTION OF EXAMPLES

Overview

In a phacoemulsification procedure, assumed herein to be performed to remove the lens of a patient's eye, a surgeon uses a phacoemulsification handpiece to insert a hollow needle into the eye. The needle is vibrated ultrasonically, causing the lens to break into particles, and an aspiration pump aspirates the particles from the eye via an aspiration line from the needle. In order to maintain the intraocular pressure (IOP) of the eye within acceptable bounds while the aspiration occurs, an irrigation pump separately irrigates the eye via an irrigation line to the needle. The irrigation flow and the aspiration flow need to be set so as to prevent the acceptable bounds being exceeded, since breaching either an upper or a lower IOP bound may cause irreparable damage to the eye.

The IOP may be monitored by a first pressure sensor, herein termed an irrigation pressure sensor, in the irrigation line. The IOP may also be monitored by a second pressure sensor, herein termed an aspiration pressure sensor, in the aspiration line. Either sensor may be located anywhere along the irrigation line or the aspiration line, in or near a handpiece, or in the console. In an example, the aspiration pressure sensor is part of an anti-vacuum system (AVS), described below, in the handpiece.

During aspiration, an occlusion to the handpiece needle, caused by lens particles being sucked to the needle, may occur. The occlusion limits the aspiration flow, so that the IOP may increase. The AVS limits vacuum transfer into the eye when the occlusion to the handpiece needle breaks. However, when the occlusion breaks and the AVS operates, the IOP may reduce.

Typically, during the procedure, the site being operated on is irrigated continuously, and the aspiration is toggled to activate the aspiration flow, as required by the surgeon, typically by the surgeon activating a foot pedal. Absent an occlusion, the toggling typically reduces the IOP, and this may be detected by the irrigation pressure sensor and/or the aspiration pressure sensor. When IOP reduction is detected, the irrigation flow rate is increased to counteract the reduction.

While the IOP changes described above may be compensated for, typically with a negative feedback loop, by changes in the irrigation and/or the aspiration flow rates provided by their respective pumps, the inventors have found that there may still be unwanted oscillations in the IOP, and these oscillations may be enhanced because of the small volume of the surgical site. Such oscillations, which may in some cases even exceed the IOP bounds described above, may be in response to inherent flow rate changes imparted into the liquids being pumped. (The pumps may impart oscillatory translational and/or rotational motion components into the liquids.) The oscillations may not be adequately compensated for, because, for example, of timing delays caused by the lengths of tubing between the pumps and the handpiece.

To reduce the oscillations, examples of the disclosure measure frequency components of the IOP oscillations, as well as phases of the components. The components and their phases may be measured both before the phacoemulsification procedure, as well as during the procedure. During the procedure a processor applies control signals to the irrigation and/or the aspiration pumps, and the control signals are configured to drive the pumps at the measured frequencies, but in antiphase.

By driving the pumps in antiphase to reduce unwanted oscillations, rather than using a negative feedback loop, examples of the disclosure overcome the problems, referred to above, causing the oscillations.

SYSTEM DESCRIPTION

FIG.1is a pictorial view of a phacoemulsification apparatus10, constructed to operate in accordance with an example of the present disclosure, being used for a phacoemulsification procedure.

FIG.1includes an inset25, and as shown in the figure and the inset apparatus10includes a phacoemulsification probe/handpiece12comprising, at a distal end13of the probe, a needle16and a coaxial irrigation sleeve17that at least partially surrounds the needle16and that creates a fluid pathway between the external wall of the needle16and the internal wall of the irrigation sleeve17. Needle16is configured to be inserted into a lens capsule18of an eye20of a patient19. Needle16is mounted on a horn14of probe12and is shown in inset25as a straight needle. However, any suitable needle may be used with the phacoemulsification probe12, for example, a curved or bent tip needle commercially available from Johnson & Johnson Surgical Vision, Inc., Irvine, CA, USA. A physician15holds handpiece12so as to perform a phacoemulsification procedure on the eye20of patient19. The physician may activate the handpiece using a foot pedal, described below with reference toFIG.2.

Handpiece12comprises a piezoelectric actuator22, which is configured to vibrate horn14and needle16in one or more vibration modes of the combined horn and needle. During the phacoemulsification procedure the vibration of needle16is used to break a cataract into small pieces.

Elements of apparatus10are under overall control of a processor38in a console28. Functions of processor38are describe in more detail below.

During the phacoemulsification procedure, an irrigation sub-system24in console28pumps irrigation fluid to irrigation sleeve17so as to irrigate the eye20. The fluid is pumped via an irrigation tubing line34running from the console28to the probe12. An aspiration sub-system26, also located in console28, aspirates eye fluid and waste matter (e.g., emulsified parts of the cataract) from the patient's eye via needle16. Aspiration sub-system26comprises a pump which produces a vacuum that is connected from the aspiration sub-system26to probe12by a vacuum aspiration tubing line46.

Irrigation sub-system24and aspiration sub-system26are both under overall control of processor38. Some or all of the functions of processor38may be combined in a single physical component or, alternatively, implemented using multiple physical components. The physical components may comprise hard-wired or programmable devices, or a combination of the two. The functions and structure of irrigation sub-system24and aspiration sub-system26are described with respect toFIG.2below.

FIG.2is a schematic block diagram illustrating irrigation sub-system24and aspiration sub-system26, according to an example of the present disclosure. Irrigation sub-system24comprises an irrigation pump68, herein by way of example assumed to comprise a progressive cavity pump (PCP) having an internal rotor64and an external stator66. Pump68is driven by a motor62, which is controlled by an irrigation pump controller60. Pump68has an encoder65, which is connected to controller60, enabling the controller to be able to register the position of rotor64with respect to stator66. Using signals from encoder65, controller60can control both the frequency and phase of operation of pump68.

Irrigation tubing line34is connected to an irrigation channel100incorporated in handpiece12. Irrigation fluid, typically a balanced salt solution, is pumped, from an irrigation fluid reservoir70, by pump68through tubing line34and irrigation channel100to irrigation sleeve17. A pressure sensor72, illustrated as being located in irrigation channel100, is coupled with the irrigation fluid so as to determine a pressure of the irrigation fluid. The sensor provides a measure of the IOP, and a connecting line92indicates that the signal generated by the pressure sensor is provided to system processor38. It will be understood that pressure sensor72may be coupled with the irrigation fluid in locations other than irrigation channel100, such as tubing line34or an AVS96(described below).

As described below, processor38uses the input from sensor72, as well as other inputs, to provide a driving signal to pump controller60, as shown by a connecting line94.

Aspiration sub-system26comprises an aspiration pump88, herein by way of example assumed to comprise a PCP having an internal rotor84and an external stator86. Pump88is driven by a motor82, which is controlled by an irrigation pump controller80. Pump88has an encoder85, which is connected to controller80, enabling the controller to be aware of and use the position of rotor84with respect to stator86. Using signals from encoder85, controller80can control both the frequency and phase of operation of pump88.

Aspiration tubing line46is connected to an aspiration channel102in handpiece12. When operative, pump88aspirates matter acquired by needle16, via channel102and tubing46, to a waste matter container108. There is an anti-vacuum system (AVS) or chamber stability system (CSS)96in line46that may be coupled with irrigation tubing line34and that is configured to limit the fluid and lens particles sucked out of the eye of the patient via the needle16when an occlusion breaks (also known as post occlusion surge).

AVS96has a pressure sensor98incorporated in the AVS and coupled with the aspiration fluid, and, as for pressure sensor72, the signal generated by sensor98is indicative of the IOP. Pressure sensor98may be coupled with the aspiration fluid by being incorporated into entities, such as aspiration tubing line46, other than AVS96. A connecting line110provides the signal from sensor98to system processor38. Processor38is configured to use the signal from sensor98, as well as other inputs as described below, to provide a driving signal to aspiration pump controller80, as shown by connecting line114.

During the procedure, physician15operates the irrigation and aspiration sub-systems (24,26), using a sub-system user interface. In an example of the disclosure a foot-pedal104acts as the sub-system user interface, and in a disclosed example the foot-pedal has four positions: a first position where the foot-pedal is not activated such that neither sub-system is activated, a second position where the irrigation sub-system alone is activated, a third position where both the irrigation and the aspiration sub-system are activated, and a fourth position where ultrasound is activated in addition to the activated irrigation and aspiration sub-systems.

Returning toFIG.1, in some examples, at least some of the functions of processor38may be carried out by suitable software stored in a memory35. The software may be downloaded to a device in electronic form, over a network, for example. Alternatively, or additionally, the software may be stored in tangible, non-transitory computer-readable storage media, such as optical, magnetic, or electronic memory.

Console28comprises a piezoelectric drive module30, which is coupled with piezoelectric actuator22, via processor38, using electrical wiring running in a cable43.

Processor38may receive user-based commands via a system user interface40, which may include setting and/or adjusting a vibration mode and/or a frequency of piezoelectric actuator22, setting and/or adjusting a stroke amplitude of needle16, and setting and/or adjusting a default irrigation rate and a default aspiration rate of irrigation sub-system24and aspiration sub-system26. Additionally, or alternatively, processor38may receive user-based commands from controls located in handpiece12, to, for example, select a trajectory for needle16.

Processor38may present results of the phacoemulsification procedure on a display36. In an example, user interface40and display36may be one and the same, such as a touch screen graphical user interface.

The procedure illustrated inFIG.1may include further elements, which are omitted for clarity of presentation. For example, physician15typically performs the procedure using a stereo-microscope or magnifying glasses, neither of which are shown. Physician15may use other surgical tools, in addition to probe12, which are also not shown to maintain clarity and simplicity.

Because, during the phacoemulsification procedure referred to herein, there is continuous irrigation as well as intermittent aspiration of eye20, the IOP in the eye varies. Examples of the present disclosure mitigate these variations, as described below.

FIG.3Ais a flowchart150of steps performed during a handpiece priming phase of the phacoemulsification procedure, andFIG.3Bis a schematic block diagram of elements of apparatus10used during the priming phase, according to an example of the present disclosure.

Before an operational phase of the procedure, when the needle of the handpiece is inserted into the patient's eye, handpiece12is primed, by enclosing needle16and sleeve17in a test chamber120. Test chamber120ensures that the output of the irrigation pump forms the input of the aspiration pump, i.e., that the irrigation fluid pumped from the irrigation pump corresponds to the aspiration fluid pumped by the aspiration pump.

In a first step152of the priming phase processor38activates both irrigation pump68and aspiration pump88, via controllers60and80, to pump liquid through needle16and sleeve17. The priming removes any air bubbles that may be present in the irrigation and aspiration lines. In an example, during the priming processor38sequentially operates, at different times, both the pumps at a common rate r1, r2, . . . rn, r1≠r2≠rn, where n is an index of the pump rate. I.e., at any given time, the irrigation pump is operated at a rate rm, and the aspiration pump is also operated at rate rm.

In a recordation step156, while the priming of step152is being performed, processor38records and stores the signals from pressure sensor72in the irrigation channel, and from pressure sensor98in the aspiration tubing line.

In an analysis step160which concludes the flowchart, and which may be performed during or after the priming of the handpiece, processor38converts the signals from sensors72and98to IOP values. The processor then performs a fast Fourier transform (FFT) on the pressure values, to identify frequency components of the pressures, as well as amplitudes and phases of the identified components. The FFT is performed for each of the different pump rates performed in step152. Typically, each frequency component has a value between approximately 0.1 Hz and approximately 10 Hz, but the components may be outside this range.

For a given pump rate, the components determined by the FFT typically include noisy components. To differentiate from the noise, in an example, for each given pump rate processor38finds the average amplitude of the frequency components and identifies components above a preset threshold amplitude. In an example, the preset threshold amplitude is ten times the average amplitude, but other examples may have the preset threshold larger or small than ten times the average.

In a disclosed example, described hereinbelow, the number of components identified in analysis step160is assumed to be two, and processor38is configured to identify, by inspecting amplitudes of the components, the two largest components greater than the threshold.

Those having ordinary skill in the art will be able to adapt the description, mutatis mutandis, for numbers of components different from two, i.e., when only one component is identified, or when three or more components are identified.

For each given pump rate processor38stores in memory35the pair of frequency values of each of the identified components, herein termed pump frequencies, as well as the phase of the components, as pairs of ordered frequency-phase values:

where n is the index indicative of the pump rate at which the frequency and phase pairs were acquired.

Processor38uses the stored frequency and phase values in an operational phase of the procedure, described below with reference toFIGS.4A,4B, and4C.

FIG.4Ais a flowchart170of steps performed during an operational phase of the phacoemulsification procedure,FIG.4Bis a schematic block diagram of elements of apparatus10used during the operational phase, andFIG.4Cillustrates simulated results acquired during the operational phase, according to an example of the present disclosure.

In an initial step172, physician15inserts needle16and sleeve17into eye20of the patient and activates the irrigation and aspiration pumps (68,88). Typically, the irrigation pump68is activated substantially continuously, and the aspiration pump88is activated as required. Physician15may use foot-pedal104for the activations. It will be understood that, in contrast to the priming phase, in the operational phase the output of the irrigation pump68does not form the input of the aspiration pump88. Rather, the output of the irrigation pump68is a liquid directed into eye20, and the input of the aspiration pump88comprises particles and/or fluid of eye20.

While the pumps are activated in the procedure, processor38acquires the signals from pressure sensor72in the irrigation channel100, and from pressure sensor98in the aspiration tubing line46. The processor38converts the acquired signals to IOP values, which are herein termed procedure IOP values, and stores the procedure IOP values.

In a processing step176implemented during the procedure, processor38performs an FFT on the stored procedure IOP values. From the FFT, the processor38identifies a frequency component with the highest amplitude, herein termed the procedure frequency. The processor38stores the procedure frequency, and the phase associated with the procedure frequency, as an ordered pair (fm, ϕm).

In a registration step180, processor38registers the pump rates being used, i.e., the rate at which controller60is driving irrigation pump68, and, if aspiration is being implemented, the rate at which controller80is driving the aspiration pump88. The rates may be identified by indexes 1, 2, . . . , n described above. The processor then retrieves from memory35the pump frequencies and phases, associated with the registered pump rates, that have been stored in step160of flowchart150. Thus, for a pump rate rn, the processor retrieves (f1n, ϕ1n) and (f2n, ϕ2n).

In a pump input step184, processor38provides control signals to controller60or controller80to drive their respective pumps, irrigation pump68and aspiration pump88, at the frequencies retrieved in step180, and at the procedure frequency stored in step176. However, the signals are configured to drive the pumps in antiphase to the retrieved and stored phases. I.e., the control signals provide the frequencies and phases: (fm,−ϕm), (f1n,−ϕ1n), and (f2n,−ϕ2n) If only irrigation is being used, then the frequencies and antiphase values are provided to irrigation controller60; if irrigation and aspiration are being used then the frequencies and antiphase values may be provided to either controller, and in one example the controller is selected to be aspiration controller80.

FIG.4Cillustrates simulated IOP vs. time results. A graph250has a mean pressure value of approximately 70 mmHg, and peak-peak oscillations of approximately 20 mmHg. The oscillations have a frequency of approximately 1.3 Hz. Graph illustrates the expected IOP variation if the steps of flowchart170are not implemented during a phacoemulsification procedure.

Examples

Example 1. A phacoemulsification system, comprising: a phacoemulsification probe (12) having an irrigation channel (100) and an aspiration channel (102), and a distal end (13) comprising a needle (16) and a sleeve (17) configured to be inserted into an eye; an irrigation pump (68) configured to pump irrigation fluid via the irrigation channel and the distal end into the eye; an aspiration pump (88) configured to pump aspiration fluid via the distal end and the aspiration channel from the eye; a first pressure sensor (72) coupled with the irrigation fluid and configured to provide a first signal indicative of intraocular pressure (IOP) in the eye; a second pressure sensor (98) coupled with the aspiration fluid and configured to provide a second signal indicative of the IOP in the eye; and a system processor (38) configured to: receive the first signal and the second signal, and responsively to at least one of the first signal and the second signal, identify at least one frequency and an associated at least one phase of the IOP, and pump at least one of the aspiration pump and the irrigation pump at the identified at least one frequency and in antiphase to the identified at least one phase.

Example 2. The system according to example 1, wherein the system processor is further configured to convert the received first and second signals to IOP values and perform a fast Fourier transform (FFT) on the IOP values, and wherein identifying the at least one frequency and the at least one phase of the IOP comprises selecting from the FFT an IOP value having a maximum amplitude.

Example 3. The system according to any of examples 1 to 2, further comprising a test chamber (120) configured to receive the needle and the sleeve, the system processor being configured to identify the at least one frequency and the at least one phase in a priming phase of a phacoemulsification procedure, wherein in the priming phase the needle and the sleeve are placed in the test chamber so that the irrigation fluid pumped by the irrigation pump comprises the aspiration fluid pumped by the aspiration pump.

Example 4. The system according to example 3, wherein in the priming phase the irrigation pump and the aspiration pump pump at a common first rate in a first time period, and in a common second rate, different from the common first rate, in a second time period different from the first time period, and wherein the system processor is configured to identify a first frequency and an associated first phase in the first time period, and a second frequency and an associated second phase in the second time period.

Example 5. The system according to any of examples 1 to 4, wherein the system processor is further configured to identify the at least one frequency and the at least one phase in an operational phase of a phacoemulsification procedure, wherein in the operational phase the needle and the sleeve are inserted into the eye so that the irrigation fluid is pumped into the eye, and the aspiration fluid comprises entities of the eye pumped therefrom.

Example 6. The system according to example 5, wherein identifying the at least one frequency and the associated at least one phase comprises storing the at least one frequency and the associated at least one phase in a priming phase of the phacoemulsification procedure performed prior to the operational phase, and retrieving the stored at least one frequency and the associated at least one phase during the operational phase.

Example 7. The system according to example 6, wherein in the priming phase the irrigation pump and the aspiration pump pump at a common rate, and wherein in the operational phase the system processor is configured to detect that at least one of the irrigation pump and the aspiration pump is pumping at the common rate, and in response to the detection retrieve the stored at least one frequency and the associated at least one phase.

Example 8. The system according to any of examples 1 to 7, wherein the irrigation pump comprises an encoder (65) configured to provide an encoding signal to the system processor, and wherein in response to receiving the encoding signal, the system processor is configured to pump the irrigation pump at the identified at least one frequency and in antiphase to the identified at least one phase.

Example 9. The system according to any of examples 1 to 8, wherein the aspiration pump comprises an encoder (85) configured to provide an encoding signal to the system processor, and wherein in response to receiving the encoding signal, the system processor is configured to pump the aspiration pump at the identified at least one frequency and in antiphase to the identified at least one phase.

Example 10. The system according to an of examples 1 to 9, wherein the irrigation pump and the aspiration pump comprise progressive cavity pumps.

Example 11. A method, comprising: providing a phacoemulsification probe (12) having an irrigation channel (100) and an aspiration channel (102), and a distal end (13) comprising a needle (16) and a sleeve (17) configured to be inserted into an eye; configuring an irrigation pump (68) to pump irrigation fluid via the irrigation channel and the distal end into the eye; configuring an aspiration pump (88) to pump aspiration fluid via the distal end and the aspiration channel from the eye; coupling a first pressure sensor (72) with the irrigation fluid so as to provide a first signal indicative of intraocular pressure (IOP) in the eye; coupling a second pressure sensor (98) with the aspiration fluid so as to provide a second signal indicative of the IOP in the eye; receiving the first signal and the second signal, and responsively to at least one of the first signal and the second signal, identifying at least one frequency and an associated at least one phase of the IOP; and pumping at least one of the aspiration pump and the irrigation pump at the identified at least one frequency and in antiphase to the identified at least one phase.