An actuator unit, a method and a computer program product
Patent Information
- Application Number
- NL2039238
- Authority / Receiving Office
- NL · NL
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-12-03
- Publication Date
- 2026-06-23
- Estimated Expiration
- 2044-12-02
Smart Images
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Abstract
Description
P138173NL00 Title: An actuator unit, a method and a computer program product The invention relates to an actuator unit for operating an ophthalmic surgical phacoemulsication device. Phacoemulsification is known as a process for disintegration ofthe lens ofan eye utilizing an ophthalmic surgical phacoemulsication device vibrating at ultrasonic frequencies. Such phacoemulsication device includes a driver unit containing a piezoelectric module for actuating, via a sonotrode, a needle having a cutting tip which is vibrated at ultrasonic frequencies to disintegrate cataractic tissue in the eye. Known phacoemulsification devices comprise a handpiece with a vibrating needle tip wherein the vibration ofthe needle tip is manually operated by a surgeon. Such known phacoemulsification devices are frequently operated by foot pedals. Manual operation and activation ofthe vibrating needle tip poses multiple risks in the eld ofphacoemulsication. A rst issue is the repulsion of a lens fragment in case a surgeon inadvertently activates the ultrasonic energy prior to making sufcient contact with a lens fragment. Then, the lens fragment is rapidly repelled away from the surgeons needle tip and away from the inuence ofthe uidics systems aspiration ow, negatively impacting the surgeons workow and therefore increasing the duration ofthe intervention. Secondly, there is a risk ofa particular iatrogenic injury whereby the surgeon can cause a posterior capsular break (a rupture ofthe posterior aspect ofthe anterior chamber), known to be one ofthe most severe surgical complications in cataract interventions. The possibility for this complication to occur is facilitatedby the fact that phacoemulsification in known devices can be unintentionally activated against the posterior capsule layers, most frequently during the initial surgical steps ofphaco lens chopping. Another major mechanism for said complication is a post-occlusion surge of aspiration pressure causedby a lens fragment. It is an object ofthe present invention to provide an actuator unit for operating an ophthalmic surgical phacoemulsication device having a reduced risk ofcomplications related to the repulsion oflens fragments and / or iatrogenic injury, more specifically a posterior capsular break. Thereto, according to the invention, an actuator unit for operating an ophthalmic surgical phacoemulsification device is provided, comprising a stack of driving piezo elements for driving a tip ofthe ophthalmic surgical phacoemulsification device, a driver circuit arranged for generating a driver signal for actuating the stack ofpiezo elements, a probing circuit arranged for generating a probing signal for ultrasonically probing an environment of the tip and a sensing circuit arranged for receiving a sensing signal resulting from probing the tip environment. The invention is at least partly based on the insight that complications occurring due to activation ofphacoemulsification while the needle tip ofthe ophthalmic surgical phacoemulsification device is not in contact with a surface it is intended to be in contact with can be mitigated by activating phacoemulsification only when the needle tip is in contact with a surface it is supposed to be in contact with andby deactivating phacoemulsification when the needle tip is in contact with a surface it is not supposed to be in contact with. By providing a design capable of detecting whether the needle tip ofthe ophthalmic surgical phacoemulsification device is in contact with a surface it is supposed to be in contact with, more specifically, ocular tissue, it is possible to activate or deactivate phacoemulsication based on the type ofsurface the needle tip is in contact with. Advantageously, the design is further adapted to distinguish and / or classify properties ofthe surface the needle tip is in contact with. A device comprising said detection capability allows for activation ofphacoemulsification only in cases when the risk for complications is minimized, i.e. when the needle tip is in contact with a surface it is supposed to be in contact with. In addition, such device allows for deactivation ofphacoemulsification ifthe operator encounters a situation posing a high risk for complications. The detection capabilitymay be implemented as a safety system complementary to the manual operation system to be controlled by a surgeon. The actuator unit may comprise a probing piezo element connected to the probing circuit for converting the probing signal into an ultrasonic interrogation signal, wherein the probing piezo element is further connected to the sensing circuit for generating a sensing signal from an ultrasonic response signal resulting from an interaction ofthe ultrasonic interrogation signal with the tip environment. The probing piezo element may further be placed in series with the stack of driving piezo elements. Then, a bespoke piezo for probing purposes is selected, having different intrinsic ceramic characteristics compared to the driving piezo elements, wherein said probing piezo characteristics are specically geared towards a higher signal to noise ratio for sensing purposes. Alternatively, the driving piezo elements are arranged for generating both the driving signal and the probing signal, and for receiving a sensing signal. In an advantageous embodiment, the actuator unit comprises a superposition module for superimposing the driver signal ofthe driver circuit to the probing signal ofthe probing circuit for feeding the driving piezo elements. The driving piezo elements may further be arranged for converting the probing signal portion from the superimposed signal into an ultrasonic interrogation signal, and the driving piezo elements are connected to the sensing circuit for generating a sensing signal from the ultrasonic response signal resulting from an interaction ofthe ultrasonic interrogation signal with the tip environment from an interaction ofan ultrasonic interrogation signal generatedby the driving piezo elements with the tip environment. In this way, a stack of driving piezo elements, preferably all having identical intrinsic ceramic characteristics, is arranged to generate a mechanical displacement with an actuation function and a sensing function simultaneously, without the need for the stack to comprise dedicated probing piezo elements. In a specific embodiment, the driver signal has a driver frequency, and the probing signal has a probing frequency that is larger than the driver frequency. The probing frequencymay be higher than 40 kHz, preferably circa 60 kHz, circa 80 kHz, circa 100 kHz or circa 120 kHz, or higher than 120 kHz. Furthermore, the probing frequencymay be centered around an oddharmonic or around multiple harmonics ofthe driver frequency. Additionally, the probing signal has a frequency spectrum, preferably a chirp spectrum. Then, analysis ofthe frequency domain ofthe sensing circuit output signal yields information which is inuenced by the surface that is in contact with the needle tip, saidinuence may be analyzed to characterize the surface which is in contact with the needle tip. Advantageously, the sensing circuit may be arranged for classifying the received sensing signal, based on a spectral behaviour ofthe sensing signal inducedby any load in the tip environment. Additionally, the sensing circuit may be arranged for classifying a sensing signals as a rst class of signals associated with tissue free tip environment, as a second class ofsignals associated with a lens fragment adjacent to the tip, and / or as a third class ofsignals associated with connective tissue adjacent to the tip. In this way, a specific profile observed in the frequency domain analysis ofthe sensing circuit output signal is mapped to characteristics ofthe surface that is in contact with the needle tip. Optionally, the sensing circuitmay be arranged for generating an auto-fire signal ifan actual sensing signal is classied as a second class of signals. The sensing circuit may further be arranged for generating a safe- stop signal ifan actual sensing signal is classified as a third class of signals. Then, the risk ofcomplications is reduced significantly in case a surgeon encounters a situation wherein the needle tip is in contact with a surface it is not supposed to be in contact with, without the surgeons manual intervention to appropriately deactivate phacoemulsification depending on the situation. The risk ofcomplications is further reducedby only allowing activation ofphacoemulsication in case the needle tip is in contact with a surface it is supposed to be in contact with. In addition, the invention relates to a method. Further, the invention relates to a computer program product for operating an ophthalmic surgical phacoemulsication device with an actuator unit according to the invention.Acomputer program productmay comprise a set ofcomputer executable instructions stored on a data carrier, such as but not limited to a ash memory, a CD or a DVD. The set of computer executable instructions, which allow aprogrammable computer to carry out the method as dened above, may also be available for downloading from a remote server, for example via the Internet. The computer program product comprises computer readable code for causing a circuit to perform at least one step ofthe method according to the invention. It should be noted that the technical features described above or below may each on its own be embodied in a system or method, i.e. isolated from the context in which it is described, separate from other features, or in combination with only a number ofthe other features described in the context in which it is disclosed. Each ofthese features may further be combined with any other feature disclosed, in any combination. The invention will be further elucidated on the basis ofexemplary embodiments which are represented in the drawings. The exemplary embodiments are given by way ofnon-limitative illustration ofthe invention. In the drawings: Fig. 1 shows a schematic cross-sectional view of a first embodiment ofan ophthalmic surgical phacoemulsication device arranged to be operated by an actuator unit according to the invention; Fig. 2 shows a schematic cross-sectional view of a second embodiment ofan ophthalmic surgical phacoemulsification device arranged to be operatedby an actuator unit according to the invention; Fig. 3 shows a block diagram ofa first embodiment ofthe actuator unit 19 for operating an ophthalmic surgical phacoemulsification device shown in Fig. 1; Fig. 4 shows a block diagram ofa second embodiment ofthe actuator unit for operating an ophthalmic surgical phacoemulsification device shown in Fig. 2; Fig. 5a and Fig. 5b show a spectral output ofthe driver circuit and the sensing circuit, respectively, ofthe ophthalmic surgical phacoemulsification device shown in Fig. 1 and Fig. 2; Fig. 6a, Fig. 6b and Fig. 6c show a spectral output ofthe sensing circuit ofthe ophthalmic surgical phacoemulsification device shown in Fig. 1 or Fig. 2 subjected to interference by varying system loads; Fig. 7 shows aow chart of a method for operating the ophthalmic surgical phacoemulsication device shown in Fig. 1 or Fig. 2; Fig. 8 shows a partialow chart of a first specific embodiment of the method shown in Fig. 7; Fig. 9 shows a partialow chart of a second specic embodiment of the method shown in Fig. 7, and Fig. 10 shows a partialow chart of a third specific embodiment of the method shown in Fig. 7. In the figures identical or corresponding parts are represented with the same reference numerals. The drawings are only schematic representations ofembodiments ofthe invention, which are given by manner ofnon-limited examples. Fig. 1 shows a schematic cross-sectional view of a first embodiment ofan ophthalmic surgical phacoemulsication device 1 arranged to be operated by an actuator unit according to the invention. The ophthalmic surgical phacoemulsication device 1 is used in modern-day cataract surgery that employs ultrasound energy for emulsifying the internal lens of the eye. The ophthalmic surgical phacoemulsification device 1 is formed as a unit including an elongate housing 2 extending along a longitudinal axis A, forming a handpiece. The elongate housing 2 has a distal end 3 and a proximal end 4. Further, the ophthalmic surgical phacoemulsication device 1 includes a tip 5 mounted to the distal end 3 ofthe elongate house 2 and aligned with the longitudinal axis A. As shown in Fig. 1, the ophthalmic surgical phacoemulsication device 1 has a sonotrode 6 having a distal end 6a and a proximal end 6b, arranged for actuating the tip 5 and accommodated in the elongate housing 2. In operation, a stack of driving piezo elements 12, also accommodated in the elongate housing 2, is used for driving the tip 5 ofthe ophthalmic surgical phacoemulsication device 1. In addition, the ophthalmic surgical phacoemulsication device 1 is provided with a probing piezo element 15 for converting a probing signal into an ultrasonic interrogation signal. In the shown embodiment, the probing piezo element 15 is placed in series with the stack of driving piezo elements 12, in particular, at a distal end ofthe stack of driving piezo element 12. In other embodiments, the probing piezo element 15 is located elsewhere, e.g. at a proximal end ofthe stack of driving piezo elements 12. The elongate housing 2 has an interior 8 accommodating the sonotrode 6. The interior 8 has a distal end 8a where the sonotrode 6 is placed such that the distal end 6a ofthe sonotrode 6 is positioned so as to actuate the tip 5. Further, the elongate housing interior 8 is provided with an elongate cavity 9, proximal to the sonotrode 6. Generally, the sonotrode 6 and the cavity 9 may be provided in series, and aligned with the longitudinal axis A. The probing piezo element 15 may be placed in series with the stack of driving piezo elements 12. In other embodiment, different configurations may be considered. Further, generally, the tip 5 and the sonotrode 6 are located such that ultrasound vibrations are transferredfrom the sonotrode 6 to the tip 5, e.g. by contacting each other. In addition, the driver signal has a driver frequency and the probing signal has a probing frequency that is larger than the driver frequency. The probing frequency is preferably higher than 40 kHz, more preferably circa 60 kHz, circa 80 kHz, circa 100 kHz or circa 120 kHz, or higher than 120 kHz. The probing frequency is centered around an odd harmonic or around multiple harmonics ofthe driver frequency. In addition, the probing signal has a frequency spectrum, preferably a chirp spectrum. In other embodiments, different frequency configurations may be considered. Fig. 2 shows a schematic cross-sectional view of a second embodiment ofan ophthalmic surgical phacoemulsification device 1 arranged to be operatedby an actuator unit according to the invention. The second embodiment shown in Fig. 2 is similar to the first embodiment ofthe ophthalmic surgical phacoemulsication device 1 shown in Fig. 1, however having another setup ofpiezo elements. In contrast to the stack of dedicated driving piezo elements 12 combined with the dedicated probing piezo element 15 ofthe ophthalmic surgical phacoemulsification device 1 shown in Fig. 1, the second embodiment ofthe device shown in Fig. 2 has a stack of driving piezo elements 12, all ofwhich are arranged for performing an actuation function and a sensing function. In this way, the stack of driving piezo elements 12 is arranged to additionally provide the effect ofthe probing piezo element 15 ofFig. 1. Further, the ophthalmic surgical phacoemulsification device 1 as shown in Fig. 2 comprises a superposition module for superimposing a driver signal to a probing signal for feeding the driving piezo elements 12. Furthermore, in the second embodiment shown in Fig. 2, the driving piezo elements 12 are arranged for converting the probing signal portion from the superimposed signal into an ultrasonic interrogation signal. The driving piezo elements 12 are further connected to a sensing circuit, described below, for generating a sensing signal from the ultrasonic response signal resulting from an interaction ofthe ultrasonic interrogation signal with the tip 5 environment from an interaction ofan ultrasonic interrogation signal generated by the driving piezo elements 12 with the tip 5 environment. Generally, the actuator unit comprises a stack of driving piezo elements for driving a tip ofthe ophthalmic surgical phacoemulsication device. Further, the actuator unit comprises a driver circuit 11, a probing circuit 14 and a sensing circuit 17. The driver circuit 1 1 is arranged for generating a driver signal for actuating the stack of driving piezo elements 12. The probing circuit 14 is arranged for generating a probing signal for ultrasonically probing an environment ofthe tip 5. Further, the sensing circuit 17 is arranged for receiving a sensing signal resulting from probing the tip environment. Fig. 3 shows a block diagram ofa first embodiment ofthe actuator unit 19 for operating an ophthalmic surgical phacoemulsification device 1 shown in Fig. 1.A controller 10 is provided which is connected to the driver circuit 1 1. The driver circuit 1 1 is arranged for generating a driver signal for actuating the stack of driving piezo elements 12. The tip 5 ofthe ophthalmic surgical phacoemulsication device 1, which is connected to the stack of driving piezo elements 12, is arranged to be driven by said stack of driving piezo elements 12. The stack of driving piezo elements 12 is further connected to a measurement circuit 13. The controller 10 is further connected to the probing circuit 14 which is arranged for generating a probing signal for ultrasonically probing an environment ofthe tip 5. The probing circuit 14 is connected to the probing piezo element 15 for converting a probing signal into an ultrasonic interrogation signal. The probing piezo element 15 is further connected to the sensing circuit 17 for generating a sensing signal from an ultrasonic response signal resulting from an interaction ofthe ultrasonic interrogation signal with the environment ofthe tip 5. In the shown embodiment, the sensing circuit 17 comprises a low noise measurement circuit arranged to detect a resulting measured electrical signal, which may be subject to interferences such as noise signals. Fig. 4 shows a block diagram ofa second embodiment ofthe actuator unit 19 for operating an ophthalmic surgical phacoemulsication device shown in Fig. 2. A controller 10 is provided which is connected to the driver circuit 1 1. In addition, the probing circuit 14 is connected to the controller 10. The driver circuit 1 1 as well as the probing circuit 14 are connected to a superposition module 18 for superimposing a driver signal to a probing signal for feeding the stack ofpiezo elements 12 arranged to generate a mechanical displacement with an actuation function as well as a sensing function, simultaneously. Therefore, the stack ofpiezo elements 12 shown in Fig. 2 is also referred to as the stack of driving and probing piezo elements 12. In the shown embodiment, the driver circuit 1 1 is arranged for generating a driver signal for actuating the stack ofpiezo elements 12, whereas the probing circuit 14 is arranged for generating a probing signal for ultrasonically probing an environment ofthe tip 5. The stack ofpiezo elements 12 is arranged to convert a probing signal into an ultrasonic interrogation signal. The tip 5 ofthe ophthalmic surgical phacoemulsification device 1 which is connected to the stack ofpiezo elements 12 is arranged to be driven by said stack ofpiezo elements 12. The superposition module 18 and the stack ofpiezo elements 12 are further connected to a measurement circuit 13. In addition, the stack of piezo elements 12 is connected to the sensing circuit 17 . Then, the measurement circuit 13 as well as the sensing circuit 17 are arranged to measure an identical output ofthe stack ofpiezo elements 12, e.g. at an identical potential. The sensing circuit 17 is arranged to generate a sensing signal from an ultrasonic response signal resulting from an interaction of the ultrasonic interrogation signal with the environment ofthe tip 5. The sensing circuit 17 comprises a low noise measurement circuit 16 arranged to detect a resulting measured electrical signal, which may be subject to interferences. Figures 5a-b show a spectral output, also referred to as a graphical representation ofthe frequency domain ofthe output ofthe driver circuit 1 1 and the sensing circuit 17, respectively, ofthe ophthalmic surgical phacoemulsification device 1 shown in Fig. 1 and Fig. 2. In the shown embodiment, the sensing circuit 17 is provided with a low-noise amplifier to lter the noise sidebands createdby a frequency-shift keying modulated pseudo-chirp. By ltering the noise sidebands created by a frequency-shift keying modulated pseudo-chirp, information indicative of a specic material present at the tip 5 is obtained, as the interference causedby different system loads inuences said noise sidebands. In Fig. 5a, a magnitude 35 ofthe spectral output ofthe driver circuit 1 1 is shown as a function offrequency 36. The first seven harmonics ofthe output signal ofthe driver circuit 1 1 are shown. More specifically, a rst harmonic 40, a harmonic 41, a thirdharmonic 42, a fourth harmonic 43, a fth harmonic 44, a sixth harmonic 45 and a seventh harmonic 46 of the output signal ofthe driver circuit 1 1 are shown. In addition, a spectral bandpass lter 39 ltering out everything except the first harmonic 40 is shown. In Fig. 5b, a magnitude 37 ofthe spectral output ofthe sensing circuit 17 is shown as a function offrequency 38 . Here, spectral output of the sensing circuit 17 includes spectral sideband signals 48, 49, 50, 51, 53, 54, 55 and 56 induced by a probing signal 52 having a frequency spectrum or spectral behaviour, also shown, generated as a frequency-shift keying modulated pseudo-chirp signal. Further, the spectral output ofthe sensing circuit 17 includes a response ofthe rst harmonic 57 ofthe output signal of the driving circuit 12 . It is noted that the probing signal 52 is centered at the third harmonic 42 ofthe driver signal ofthe driving circuit 1 1. In addition, a spectral high pass lter 47 filtering out the rst harmonic 57 is shown. A frequency-shift keying modulated pseudo-chirp signal is a wide- band electrical signal exploiting a spectral leakage that occurs ifwe deploy the probing signal as a chirp. The theoretical bandwidth ofa chirp can be defined in frequency domain as f(t) = fo + Kt. In practice this means that for an up-chirp we will sweep from an initial frequency ( fo) up to an end frequency (fo + KT), whereKcorresponds to the rate ofchange offrequency (speed) ofthe chirp andT corresponds to the time duration ofthe chirp. The theoretical bandwidth ofsuch a chirp would be just Af=KT. However, depending on the speedK and duration T, a chirp will actually create a very large tail ofsideband noise, this noise is normally undesirable in electrical design, however in the present application serving a purpose a purpose of retrieving rich information ofthe characteristics ofthe load. It appears that a step change in frequency, effectively anFSK modulation with a chirp-like bandwidth, enables maximum power delivery ofthe noise sidebands 48-51, 53-56. Generally, the frequency ofthe probing signal is higher than circa 40 kHz, preferably circa 60 kHz, circa 80 kHz, circa 100 kHz or circa 120 kHz, or higher than 120 kHz. As an example, the frequency ofthe probing signal is centered around an odd harmonic or around multiple harmonics of the driver frequency, such as around the third harmonic, shown in Fig. 5b, or around the fifth harmonic. The sensing circuit 17 is arranged for classifying the received sensing signal, based on a spectral behaviour ofthe sensing signal induced by any load in the tip 5 environment. In the shown example, the sensing circuit 17 is arranged for classifying a sensing signals as a rst class of signals associated with tissue free tip environment, as a second class of signals associated with a lens fragment adjacent to the tip, such as a hard lens, and / or as a third class ofsignals associated with connective tissue adjacent to the tip. It is noted that the sensing circuit 17may be arranged to classify the sensing signals into the three classes mentioned above, or into a subset ofthe three classes, e.g. two classes or one class only. As an example, the sensing circuit 17 may be arranged to identify a sensing signal to belong to either the first class, or the second class or the third class. As another example, the sensing circuit 17 may be arranged to identify a sensing signal to belong to either the rst class or the second class, or to belong to either the second class ofthe third class. As yet another example, the sensing circuit 17 may be arranged to identify a sensing signal to belong to the rst class. Further, the sensing circuit 17may be arranged to classify the sensing signals in even more than three classes, e.g. four or ve classes. Furthermore, the sensing circuit 17 is arranged for generating an auto-fire signal ifan actual sensing signal is classied as a second class of signals and / or for generating a safe-stop signal ifan actual sensing signal is classified as a third class of signals. Figures 6a-c show a spectral output ofthe sensing circuit 17 ofthe ophthalmic surgical phacoemulsication device 1 shown in Fig. 1 and Fig. 2 subjected to interference by different system loads. Each ofthe frequency domain representations corresponds to a situation wherein a specic material is in touching or near or contact with the tip 5 ofthe device 1. Knowledge ofhow a specific material present near the tip 5 may inuence the spectral behaviour ofthe received sensing signal received by the sensing circuit 17 ofthe ophthalmic surgical phacoemulsification device 1 allows to construct a database with classier proles 58a-c. Each classifier profile 58a-cmay correspond with a specic frequency domain prole, from which the material present at the tip 5 can be deduced. Mapping 61 a measured spectral behaviour to a specific material present at the tip 5 by using said database ofclassier proles 58a-cmay be performed by means of artificial intelligence, preferably by means ofmachine learning, more preferably by means of analysis using a support vector machine 59 specifically trained on said classifier profiles 58a-c or other hardware component arranged for classifying such as a processing unit or rule based machine. In Fig. 6a-c, it is shown that the spectral responses 58 are fed 62 into the support vector machine 59 for comparison and classification, resulting in an output 61 reecting a classification. Fig. 6a represents the spectral output ofthe sensing circuit 17 of the ophthalmic surgical phacoemulsication device 1 in case the tip 5 does not make contact with any kind ofmaterial. In this case, a rst classifier profile 58a resembles an upside-downV shape. Furthermore, Fig. 6b shows the spectral output ofsensing circuit 17 ofthe ophthalmic surgical phacoemulsification device 1 in case the tip 5 is in contact with lens tissue 63. In this case, a second classifier profile 58b resembles an upside-downV shape, wherein the right leg ofthe upside-downV shape is attened or higher compared to the right leg ofthe first classifier profile 58a shown in Fig. 6a. Fig. 6c shows the spectral output ofsensing circuit 17 ofthe device 1 in case the tip 5 is in contact with capsular tissue 64. In this case, the third classifier profile 58c resembles an upside-downV shape, wherein the right leg ofthe upside-downV shape is lower compared to the right leg of the first classifier profile shown in Fig. 6a. Figure 7 shows aow chart of a method for operating the ophthalmic surgical phacoemulsication device 1 shown in Fig. 1 or Fig. 2. The method 130 comprises a step 31 ofproviding an actuator unit 19 as described above for operating an ophthalmic surgical phacoemulsification device, a step 32 of generating a driver signal for actuating the stack of piezo elements, a step 33 ofgenerating a probing signal for ultrasonically probing an environment ofthe tip 5, and a step 34 ofreceiving a sensing signal resulting from probing the tip 5 environment. Fig. 8 shows a partialow chart of a first specific embodiment of the method shown in Fig. 7. Here, the rst specic embodiment ofthe method 28 is also referred to as auto-fire, and comprises additional steps, including a step 2 1 of, based on the sensing signal, detect ifthe sensing signal is indicative oflens tissue being present at the tip 5, i.e. classify the sensing signal as a rst class ofsignals associated with tissue free tip environment. The first specific embodiment ofthe method 28 further comprises a step 22 checking whether an activation switch is enabled. Said switchmay be implemented as a foot pedal to be operated by a surgeon. The rst specific embodiment ofthe method 28 further comprises a step 23 of activating phacoemulsication only ifthe detection step 2 1 indicates that lens tissue is present at the tip 5 and ifthe activation switch is enabled. Fig. 9 shows a partialow chart of a second specic embodiment of the method shown in Fig. 7. Here, the second specic embodiment ofthe method 29 is also referred to as safe-stop, and further comprises a step 24 of detecting ifthe tip 5 during use transitions from lens tissue to posterior capsule layers tissue by means ofthe sensing circuit 17 , i.e. classify the sensing signal as a third class ofsignals associated with connective tissue adjacent to the tip. The second specific embodiment ofthe method 29 further includes a step 25 ofstopping phacoemulsification ifthe tip 5 during use transitions from lens tissue to posterior capsule layers tissue. Fig. 10 shows a partialow chart of a third specific embodiment of the method shown in Fig. 7. Here, the third specific embodiment ofthe method 30 is also referred to as occlusion- pre-emption, and comprises a step 26 of detecting if a large fragment oflens is present at the tip 5 by means of sensing circuit 17 , i.e. classify the sensing signal as a second class of signals associated with a lens fragment adjacent to the tip. The third specic embodiment ofthe method 30 further includes a step 27 ofstopping phacoemulsification if a large fragment oflens is present at the tip 5. The method for operating an ophthalmic surgical phacoemulsification device can also at least partially be performed using a computer program comprising instructions for causing a an actuator unit or a circuit thereof to perform at least one step ofthe method according to the invention. All (sub)steps can in principle be performed on a single processor. However, it is noted that at least one (sub)step can be performed on a separate processor.A processor can be loaded with a specific software module. The circuit may comprise a driver circuit, a probing circuit and / or a sensing circuit. In further embodiments, there may be a multiple number of circuits, wherein each ofthe circuits may comprise a driver circuit, a probing circuit and / or a sensing circuit. It is noted that embodiments comprising a multiple number of circuits may be arranged as a distributed system ofcircuits. The invention is not restricted to the embodiments described herein. It will be understood that many variants are possible. It is noted that the actuator unitmay be provided with a single probing piezo element or a multiple number ofprobing piezo elements, e.g. arranged in series. These and other embodiments will be apparent for the person skilled in the art and are considered to fall within the scope ofthe invention as defined in the following claims. For the purpose ofclarity and a concise description features are described herein as part ofthe same or separate embodiments. However, it will be appreciated that the scope ofthe inventionmay include embodiments having combinations of all or some of the features described.
Claims
1. Actuator unit for operating an ophthalmic phaco- emulsification device, comprising: - a stack of drive piezo elements for driving a tip of the ophthalmic surgical phacoemulsification device; - a drive circuit designed to generate a drive signal for activating the stack of piezo elements; - a scanning circuit designed to generate a scanning signal for ultrasonic scanning of the tip's area, and - a sensing circuit designed to detect a sensing signal to receive that results from scanning the tip environment.
2. Actuator unit according to claim 1, comprising a scanning piezo- element that is connected to the scanning circuit for converting the scan signal to an ultrasonic interrogation signal, where the scan- piezo element is further connected to the sensing circuit for the generating a sensing signal from an ultrasonic response signal that results from an interaction of the ultrasonic interrogation signal with the tipping environment.
3. Actuator unit according to claim 2, where the sensing piezo element is placed in series with the stack of drive piezo elements.
4. Actuator unit within the meaning of claim 1, comprising a superposition module for superimposing the drive signal of the drive circuit on the scanning signal of the scanning circuit for the Powering the drive piezo elements.
5. Actuator unit according to claim 4, where the drive piezo- elements are configured to the scanning signal part of the to convert superimposed signal into an ultrasound interrogation signal, and where the drive piezo elements are connected to the sensing circuit for generating a observation signal from the ultrasonic response signal resulting from a interaction of the ultrasound generated by the drive piezo elements interrogation signal with the tip environment.
6. Actuator unit according to one of the preceding claims, whereby the the drive signal has a drive frequency, and where the scan signal has a scanning frequency that is higher than the drive frequency.
7. Actuator unit according to claim 6, where the scanning frequency is higher is then 40 kHz, preferably approximately 60 kHz, approximately 80 kHz, approximately 100 kHz or approximately 120 kHz, or higher than 120 kHz.
8. Actuator unit according to claim 6 or 7, where the scanning frequency is centered around an odd harmonic frequency or around multiple harmonic frequencies of the drive frequency.
9. Actuator unit according to one of the preceding claims 6-8, where the scanning signal has a frequency spectrum, preferably a chirp spectrum 10. Actuator unit in accordance with one of the preceding claims, where the The sensing circuit is configured to the received sensing signal to classify based on the spectral behavior of the observation signal caused by any load in the tipping environment.
11. Actuator unit according to claim 10, where the The sensing circuit is designed to a sensing signal classify as a first class of signals associated with a tissue-free tipping environment, as a second-class signals associated with a lens fragment near the tip, and / or associated with third-class signals with connective tissue near the tip.
12. Actuator unit according to claim 11, where the The sensing circuit is configured to generate an auto-fire signal. if a current observation signal is classified as a second Class signals.
13. Actuator unit within the meaning of claim 11 or 12, where the The sensing circuit is configured to generate a safe-stop signal. if a current detection signal is classified as a third class signals 14. Procedure for operating an ophthalmic phaco- emulsification device, comprising the steps of: - the provision of an actuator unit in accordance with one of the preceding conclusions for operating an ophthalmic phacoemulsification device; - generating a drive signal to activate the stack piezo elements; - generating a scanning signal for the ultrasonic scanning of a surroundings of the tip; and - receiving a sensory signal resulting from scanning of the tipping environment.
15. Computer program-product for operating a ophthalmic surgical phacoemulsification device with an actuator unit according to one of the preceding conclusions, comprising computer-readable code for the switching on the actuator unit to execute the steps of: - generating a drive signal to activate the stack piezo elements; - generating a scanning signal for the ultrasonic scanning of a surroundings of the tip; and - receiving a sensory signal resulting from scanning of the tipping environment.