Phacoemulsification Needle Motion to Prevent Lens Capsule Vortices
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Solution Overview
Problem
Phacoemulsification procedures face challenges with vortex formation in the emulsified media due to rotating needle motion, which can cause strong currents within the lens capsule, and existing methods to mitigate this, such as using low power or low duty cycle, are ineffective.
Innovation Solution
A processor-controlled bidirectional rotational motion of the phacoemulsification needle is implemented, alternating the rotation direction quickly to avoid vortex formation, combined with concurrent longitudinal vibration, using driving pulses with varied phase relationships among the driving signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the needle rotates unidirectionally to emulsify the lens, then emulsification efficiency is improved, but fluid vortices form causing strong currents within the lens capsule
Solution Approach 1:
The needle rotation direction is periodically reversed using alternating drive signals to the piezoelectric crystals. The controller switches between clockwise and counter-clockwise rotation in a periodic manner, which prevents the formation of persistent vortices while maintaining continuous emulsification action. This periodic reversal of rotation direction allows the system to achieve both efficient emulsification and vortex avoidance.
2Object-affected harmful factors
If low power or low duty cycle is used to reduce vortex formation, then fluid currents are reduced, but emulsification time increases
Solution Approach 1:
The system uses high power and high duty cycle operation with periodic reversal of needle rotation direction. By alternating between clockwise and counter-clockwise rotation at high power levels, the system maintains strong emulsification capability while the periodic direction changes prevent vortex persistence, thus avoiding the need to reduce power or duty cycle.
Solution Approach 2:
Instead of reducing power to avoid vortices, the system inverts the approach by using high power with periodic reversal of rotation direction. The controller applies drive signals that reverse the rotation direction, causing vortices to dissipate before they can cause harmful effects, thereby allowing high power operation without increasing vortex-related problems.
3Object-generated harmful factors
If the needle vibrates purely torsionally to reduce cavitation, then cavitation effects are reduced, but tissue disintegration is insufficient leading to frequent needle occlusions
Solution Approach 1:
The system combines both longitudinal and torsional vibrations in the needle operation. The piezoelectric crystals generate composite vibration modes that include both longitudinal expansion/contraction and torsional rotation. This merging of vibration types provides sufficient tissue disintegration to prevent needle occlusions while the torsional component helps reduce cavitation effects compared to pure longitudinal vibration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively minimizes fluid vortices, allowing for efficient emulsification with strong power and high duty cycle, reducing the time required to emulsify the lens.
Implementation Method 1
A surgical instrument includes a handpiece that has a piezoelectric transducer, and a needle having a free distal tip and a supported end that is attached to the handpiece. A circuit drives the piezoelectric transducer to periodically longitudinally expand and longitudinally contract at a driving frequency.
Implementation Method 2
The tip vibrates at ultrasonic frequency to sculpt and emulsify the cataract while a pump aspirates particles and fluid from the eye through the tip.
Implementation Method 3
a pump aspirates particles and fluid from the eye through the tip
Data Source
AI summary
A system and method for operating a medical probe, the method including driving a tip of the medical probe to cause rotation of the tip (i) in a clockwise trajectory in a plane perpendicular to a longitudinal axis during first time intervals, and (ii) in a counterclockwise trajectory in the plane during second time intervals that are interleaved with the first time intervals.