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EP-4380520-B1 - ELECTRONICALLY DETECTING PHACOEMULSIFICATION TIP ENGAGEMENT WITH A LENS

EP4380520B1EP 4380520 B1EP4380520 B1EP 4380520B1EP-4380520-B1

Inventors

  • GOVARI, ASSAF
  • Beeckler, Christopher Thomas
  • Gliner, Vadim
  • SITNITSKY, ILYA
  • FUCHS, AMIT
  • KEYES, JOSEPH THOMAS
  • AHARON, ERAN

Dates

Publication Date
20260506
Application Date
20220713

Claims (10)

  1. A system (10), comprising: a phacoemulsification handpiece (12) comprising a needle (16) and one or more piezoelectric crystals (22), the needle being configured to be inserted into an eye (20) of a patient and be vibrated by driving the one or more piezoelectric crystals (22) in the handpiece with one or more electrical signals having different respective frequencies using one or more respective drive modules; and a processor (38), which is configured to: tune the frequencies of the electrical signals to respective one or more target frequencies, and register respective electrical impedances seen by the drive modules, wherein the processor is configured to tune the frequencies of the electrical signals to respective one or more target frequencies by detuning one or more of the frequencies off-resonance, in order to have a decrease in electrical impedance magnitude with an increased mechanical load on the needle; and in response to an electrical impedance seen by at least one of the drive modules undergoing a change exceeding a preset impedance change, provide an indication that material in the eye surrounding the needle has changed.
  2. The system according to claim 1, wherein the processor is further configured to, in response to an electrical impedance seen by at least one of the drive modules undergoing a change, change a level of vibration of the needle.
  3. The system according to claim 1, wherein the processor is configured to tune the one or more frequencies by setting the target frequencies to be respective resonance frequencies of the one or more piezoelectric crystals as measured by the drive modules.
  4. The system according to claim 3, wherein tuning the frequencies comprises setting the target frequencies to be respective resonance frequencies of the one or more piezoelectric crystals as measured by the drive modules, so as to differentiate between the needle engaging with the material, and the needle disengaging from the material.
  5. The system according to claim 4, wherein the material is lens material.
  6. The system according to claim 1, wherein the change in the impedance is in response to one of the needle engaging with the material of the eye, and the needle disengaging from the material of the eye.
  7. The system according to claim 1, wherein the processor is configured to provide an indication by providing one of an audio and visual indication.
  8. The system according to claim 1, wherein the processor is configured to provide an indication by providing vibratory indication.
  9. The system according to claim 1, wherein the material is lens material.
  10. A system, comprising: a phacoemulsification handpiece comprising a needle (16) and one or more piezoelectric crystals (22), the needle being configured to be inserted into an eye of a patient and be vibrated by driving the one or more piezoelectric crystals in the handpiece with one or more electrical signals having different respective frequencies using one or more respective drive modules; and a processor, which is configured to: tune the frequencies of the electrical signals to respective one or more target frequencies, and register respective electrical impedances seen by the drive modules, wherein the processor is configured to tune the frequencies of the electrical signals to respective one or more target frequencies by detuning one or more of the frequencies off-resonance, in order to have a decrease in electrical impedance magnitude with an increased mechanical load on the needle; and in response to an electrical impedance seen by at least one of the drive modules undergoing a change exceeding a preset impedance change, change a level of vibration of the needle.

Description

FIELD OF THE DISCLOSURE The present disclosure relates generally to systems and probes that utilize piezoelectric vibration, and particularly to phacoemulsification systems and probes. BACKGROUND OF THE DISCLOSURE A cataract is a clouding and hardening of the eye's natural lens, a structure which is positioned behind the cornea, iris, and pupil. The lens is mostly made up of water and protein and as people age these proteins change and may begin to clump together obscuring portions of the lens. To correct this, a physician may recommend phacoemulsification cataract surgery. In the procedure, the surgeon makes a small incision in the sclera or cornea of the eye. Then a portion of the anterior surface of the lens capsule is removed to gain access to the cataract. The surgeon then uses a phacoemulsification probe, which has an ultrasonic handpiece with a needle. The tip of the needle vibrates at ultrasonic frequency to sculpt and emulsify the cataract while a pump aspirates particles and fluid from the eye through the tip. Aspirated fluids are replaced with irrigation of a balanced salt solution to maintain the anterior chamber of the eye. After removing the cataract with phacoemulsification, the softer outer lens cortex is removed with suction. An intraocular lens (IOL) is then introduced into the empty lens capsule restoring the patient's vision. Various techniques to control an ultrasonic transducer of a surgical tool were proposed in the patent literature. For example, International Patent Application Publication WO 2021/119616 describes systems and methods for controlling vibrations of an ultrasonic handpiece that generates an AC drive signal applied to a transducer of the ultrasonic handpiece to vibrate a tip of the ultrasonic handpiece. A property relating to a stiffness of tissue being contacted by the vibrating tip is determined based on a measured voltage and a measured current of the AC drive signal. A target displacement for the tip is determined based on the tissue property, and the AC drive signal is adjusted to achieve the determined target displacement. WO9211814A1 describes an apparatus for operating on the human eye which detects changes in load, more specifically, mechanical impedance, of a transducer and controls aspiration based on the load changes. The present disclosure will be more fully understood from the following detailed description of the examples thereof, taken together with the drawings in which: BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a pictorial view of a phacoemulsification system constructed to operate in accordance with an example of the present disclosure;Fig. 2 is a block diagram schematically illustrating a multi-channel piezoelectric drive system, in accordance with an example of the present disclosure;Fig. 3 is a schematic graph showing the electrical impedance magnitude of an ultrasonic transducer as a function of driving frequency for a given mechanical load, in accordance with an example of the present disclosure; andFig. 4 is a flow chart describing steps providing a physician with an indication that a needle of a phacoemulsification probe has contacted an eye lens of a patient, in accordance with examples of the present disclosure. SUMMARY The invention provides a system as defined by the appended independent claims, with certain embodiments defined in the dependent claims. Where methods of treatment by surgery are described below, these are provided for context and understanding of the invention, but the methods themselves do not form part of the claimed invention. DETAILED DESCRIPTION OF EXAMPLES OVERVIEW A phacoemulsification system typically drives a piezoelectric actuator included in a phacoemulsification probe/handpiece to vibrate a needle of a phacoemulsification probe during a cataract procedure. The piezoelectric actuator of the phacoemulsification probe may be designed to vibrate, in resonance, in a single mode or in multiple modes simultaneously, where each mode has a given "natural" resonant frequency. At resonance, the actuator electrical impedance experienced by a driving circuitry is minimal. However, the resonance frequency may drift during phacoemulsification, for example due to change in mechanical loads on the vibrating needle, which thereby changes the experienced electrical impedance. An important function of an ultrasonic driver circuitry is to locate and track the desired resonance frequency. Examples of the present disclosure that are described herein provide a technique for detecting vibrating needle engagement with the lens, and disengagement of the needle from the lens, by measuring electrical impedances seen by one or more electronic modules driving one or more respective piezoelectric crystals vibrating the needle. The needle is typically configured to be in mechanical resonance, but as noted above, the resonant frequency changes according to the mass of matter in the eye that couples with the needle. A change in mechanical resonan