Patent Application
20240108503
The present disclosure relates to phacoemulsification systems, and in particular, but not exclusively to, intraocular pressure control in phacoemulsification systems.
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. Before the procedure, the surgeon numbs the area with anesthesia. Then a small incision is made in the sclera or clear cornea of the eye. Fluids are injected into this incision to support the surrounding structures. The anterior surface of the lens capsule is then removed to gain access to the cataract. The surgeon then uses a phacoemulsification probe, which has an ultrasonic handpiece with a titanium or steel needle. The tip of the needle vibrates at ultrasonic frequency to sculpt and emulsify the cataract while a pump aspirates lens particles and fluid from the eye through the tip. The pump is typically controlled with a microprocessor.
Any suitable pump may be used, for example, a peristaltic and/or a venturi type of pump. 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 introduced into the empty lens capsule. Small struts called haptics hold the IOL in place. Once correctly installed the IOL restores the patient's vision.
The present disclosure will be understood from the following detailed description, taken in conjunction with the drawings in which:
During phacoemulsification, fluid and cataract particles are aspirated from the eye and irrigation fluid is directed into the eye to replace lost fluid and maintain a stable eye pressure. It is typically desired to control the irrigation and aspiration flow in a manner that maintains a steady IOP (intraocular pressure). The balance between aspiration and irrigation is a fine balance which needs to be maintained to prevent intraocular pressure (TOP) exceeding safe limits. Both too much and too little IOP may be dangerous for the eye.
For example, if aspiration is increased to remove cataract particles from the eye, irrigation also needs to be increased. The flow controller managing the aspiration and irrigation pumps may have difficulty in maintaining a very steady IOP (without fluctuations). Using a pressure sensor to monitor the IOP and adjusting the irrigation pump rate according to the monitored IOP may help. However, it takes time for the irrigation pump to achieve the adjusted flow rate and for the new pump rate to be propagated along the irrigation tubing. By the time the desired flow rate is achieved, the IOP may have changed so that the present adjustment is no longer suitable.
In some exemplary modes, a trend in the IOP is monitored during a phacoemulsification procedure and used to predict the IOP forward going (e.g., 100 milliseconds from the current time). The IOP at a future time is predicted (e.g., computed) based on the current IOP as provided by a pressure sensor close to the eye (e.g., in an irrigation channel of the phacoemulsification probe), or in the eye (e.g., on another probe inserted into the eye), and one or more indicators as how the IOP is changing or will change over time. The predicted IOP for the future time is then used to determine a desired flow rate for the irrigation pump to maintain the actual IOP at, or around, a given IOP. In some exemplary modes, a controller for the pumps includes a PID controller having control parameters which are set based on the predicted IOP and the given IOP at which the actual IOP should be maintained. In some exemplary modes, the ability to predict the future IOP may be enhanced by the flexible irrigation tubing smoothing the changes in IOP.
Indicators of how the IOP is changing may include one or more of the following: a flow rate of the aspiration fluid (which may be assumed to be equal to the rate of the aspiration pump); a rate of change of the flow rate of the aspiration fluid; a change of the intraocular pressure over time; and a rate of change of the intraocular pressure over time. In some exemplary modes, for smooth changes in TOP (below a threshold gradient), the prediction may be expected to provide improved results. If the current slope of the IOP is above the threshold gradient, this predictive feature may be turned off.
In some exemplary modes, if the IOP is changing too quickly, the predicted IOP may not be an accurate reflection of the actual future IOP and therefore, the predictive feature may be turned off.
Reference is now made to
In some exemplary modes, system 20 comprises a medical instrument, in the present example a phacoemulsification handpiece, also referred to herein as a tool 55, used by a surgeon 24 to carry out the cataract surgery. In other exemplary modes, system 20 may comprise other surgical tools, such as but not limited to an irrigation and aspiration (I/A) handpiece, a diathermy handpiece, a vitrectomy handpiece, and similar instruments.
Reference is now made to an inset 21 showing a sectional view of the surgical procedure carried out in an eye 22 of a patient 23. In some exemplary modes, surgeon 24 applies tool 55 for treating eye 22, and in the present example, surgeon 24 inserts a needle 88 of tool 55 into eye 22. In the example of inset 21, during a cataract surgical procedure, surgeon 24 inserts needle 88 into a capsular bag 89 so as to emulsify a lens 99 of eye 22.
Reference is now made back to the general view of
In some exemplary modes, generator 44 is electrically connected to tool 55, via a plurality of wires referred to herein as an electrical cable 37. Generator 44 is configured to generate one or more voltage periodic (e.g., sinusoidal) signals, also referred to herein as periodic signals, having one or more frequencies, respectively. Generator 44 is further configured to generate a plurality of driving signals, so as to vibrate needle 88 of tool 55 in accordance with a predefined pattern, so as to emulsify lens 99 of eye 22.
In some exemplary modes, processor 34 typically comprises a general-purpose computer, with suitable front end and interface circuits for controlling generator 44, pumping sub-system 42 and other components of system 20.
In practice, some or all of the functions of the processor 34 may be combined in a single physical component or, alternatively, implemented using multiple physical components. These physical components may comprise hard-wired or programmable devices, or a combination of the two. In some exemplary modes, at least some of the functions of the processor 34 may be carried out by a programmable processor under the control of suitable software. This 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.
In some exemplary modes, system 20 comprises an ophthalmic surgical microscope 11, such as ZEISS OPMI LUMERA series or ZEISS ARTEVO series supplied by Carl Zeiss Meditec AG (Oberkochen, Germany), or any other suitable type of ophthalmic surgical microscope provided by other suppliers. Ophthalmic surgical microscope 11 is configured to produce stereoscopic optical images and two-dimensional (2D) optical images of eye 22. During the cataract surgery, surgeon 24 typically looks though eyepieces 26 of ophthalmic surgical microscope 11 for viewing eye 22.
In some exemplary modes, console 33 comprises a display 36 and input devices 39, which may be used by surgeon 24 for controlling tool 55 and other components of system 20. Moreover, processor 34 is configured to display on display 36, an image 35 received from any suitable medical imaging system for assisting surgeon to carry out the cataract surgery.
This particular configuration of system 20 is shown by way of example, in order to illustrate certain problems that are addressed by exemplary modes of the present disclosure and to demonstrate the application of these exemplary modes in enhancing the performance of such a system. Exemplary modes of the present disclosure, however, are by no means limited to this specific sort of example system, and the principles described herein may similarly be applied to other sorts of ophthalmic and other minimally invasive and surgical systems.
Reference is now made to
The system 20 also includes a sensor 59 (e.g., pressure sensor) configured to provide a signal indicative of current intraocular pressure in the eye 22. In some exemplary modes, the sensor 59 is disposed in the irrigation channel 53. In other exemplary modes the sensor 59 may be placed at the surgical site, for example on an additional probe that is concurrently positioned within eye 22.
The system 20 also includes an aspiration tube 31 configured to be connected to probe 25 and to convey aspiration fluid from the eye 22. The phacoemulsification probe 25 also includes an aspiration channel 61 to carry aspiration fluid from the eye 22 to the aspiration tube 31. The aspiration channel 61 extends from the distal end of the needle 88 to the proximal end of the phacoemulsification probe 25. The system 20 includes an aspiration pump 41 configured to be connected to the aspiration tube 31 and to pump the aspiration fluid from the eye 22.
The system 20 includes a pump controller 43 configured to control respective flow directions and flow rates of the aspiration pump 41 and the irrigation pump 57. In some exemplary modes, the pump controller 43 includes a proportional-integral-derivative (PID) controller 67, which is configured to control the irrigation pump 57 and the aspiration pump 41 responsively to control parameters.
The irrigation pump 57, aspiration pump 41, and pump controller 43 are comprised in the pumping sub-system 42. In some embodiments, the aspiration pump 41 and/or irrigation pump 57 may be a progressive cavity pump (PCP). For a PCP, the flow rate through the PCP is known based on the rotation of the rotor (e.g., revolutions per minute (RPM)).
In some exemplary modes, the pump controller 43 includes an encoder 63, which is configured to provide the flow rate (e.g., RPM) of the aspiration pump 41 and/or the irrigation pump 57 to the pump controller 43 intermittently and/or upon request.
The pressure and/or flow rate provided by aspiration pump 41 may be selectively adjusted by a user with a user interface device 45, e.g., foot pedal. Pump controller 43 receives a command from user interface device 45 and controls the flow direction and flow rate of the aspiration pump 41 based on the command received. User input device 45 may include one or more of the following: a gyroscope, a variable resistor, and/or a strain gauge, by way of example for sensing input from the user. In some exemplary modes, when the user interface device is a foot pedal, the flow rate is adjusted based on the user pressing or releasing the foot pedal. Optionally, user interface device 45 is a virtual device on a display screen.
In practice, some or all of the functions of the pump controller 43 may be combined in a single physical component or, alternatively, implemented using multiple physical components. These physical components may comprise hard-wired or programmable devices, or a combination of the two. In some exemplary modes, at least some of the functions of the pump controller 43 may be carried out by a programmable processor under the control of suitable software. This 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.
Reference is now made to
The pump controller 43 is configured to receive the signal provided by the sensor 59 (block 104). In some exemplary modes, the pump controller 43 is configured to compute the current intraocular pressure responsively to the provided signal (block 106).
In some exemplary modes, when the aspiration pump is a PCP, the flow rate of the aspiration fluid is based on an RPM of PCP rotor. The encoder 63 is configured to provide the flow rate to the pump controller 43. Therefore, the pump controller 43 is configured to receive the flow rate from the encoder 63 over time (block 108). The flow rate of the aspiration fluid may be used in the computation of the IOP at the future time as described in more detail below. Additionally, or alternatively, the rate of change of the flow rate of the aspiration fluid may be used in the computation of the TOP at the future time as described in more detail below.
In some exemplary modes, if the TOP is changing too quickly, the predicted TOP may not be an accurate reflection of the actual future TOP and therefore, the predictive feature may be turned off. Therefore, optionally, at a decision block 110, the pump controller 43 determines if the change and/or rate of change of TOP and/or the aspiration flow rate exceeds a given limit (or limits). If the change and/or rate of change of TOP and/or aspiration flow rate exceeds the given limit(s) then the TOP at the future time computed from the change and/or rate of change of TOP and/or the aspiration flow rate may not provide useful results. Therefore, if the change and/or rate of change of TOP and/or the aspiration flow rate exceed the given limit(s) the pump controller 43 is configured to set the future TOP to be equal to the current computed TOP (block 112). If the change and/or rate of change of IOP and/or the aspiration flow rate does not exceed the given limit(s), the pump controller 43 is configured to compute the future TOP as described in more detail below (block 114). The given limits may be determined by observing over a period of time, the computed value of the TOP at the future time and the actual values of the TOP at the future time and the various factors contributing to the computed value of the TOP at the future time.
The pump controller 43 is configured to compute the value of intraocular pressure at the future time responsively to the provided signal and an indicator of change in the intraocular pressure over time. In some exemplary modes, the pump controller 43 is configured to compute the value of the intraocular pressure at the future time responsively to the computed current intraocular pressure and the indicator of change in the intraocular pressure over time.
In some exemplary modes, the pump controller 43 is configured to compute the value of the intraocular pressure at the future time responsively to the provided signal (or the computed current intraocular pressure) and at least one of the following: a flow rate of the aspiration fluid; a rate of change of the flow rate of the aspiration fluid; a change of the intraocular pressure over time; and a rate of change of the intraocular pressure over time.
For example, the TOP at the future time may be computed as a function of:
A, B and C are parameters which may be set and adjusted based on comparing computed IOPs at future times and actual IOPs at the respective future times so as to minimize the difference over time between the computed future IOPs and the actual IOPs at the respective future times. In some exemplary modes, one or two of the parameters may set to zero.
The pump controller 43 is configured to control the irrigation pump 57 to adjust a flow rate of the irrigation fluid to maintain the intraocular pressure at a given intraocular pressure (e.g., a default IOP or an IOP set by the physician) responsively to the computed value of the intraocular pressure at the future time (block 116). In some exemplary modes, the pump controller 43 is configured to set control parameters of the proportional-integral-derivative (PID) controller 67 responsively to the given intraocular pressure and the computed value of the intraocular pressure at the future time (block 118).
As used herein, the terms “about” or “approximately” for any numerical values or ranges indicate a suitable dimensional tolerance that allows the part or collection of components to function for its intended purpose as described herein. More specifically, “about” or “approximately” may refer to the range of values ±20% of the recited value, e.g., “about 90%” may refer to the range of values from 72% to 108%.
Various features of the disclosure which are, for clarity, described in the contexts of separate examples may also be provided in combination in a single example. Conversely, various features of the disclosure which are, for brevity, described in the context of a single example may also be provided separately or in any suitable sub-combination.
The examples described above are cited by way of example, and the present disclosure is not limited by what has been particularly shown and described hereinabove. Rather the scope of the disclosure includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.
