Glossary of Ultrasonic Technology Terminology
The following terms are commonly used in reference to the ultrasonic technology of phacoemulsification.
The formation of gas bubbles arising from the aqueous in response to pressure changes at the phaco tip. The bubbles expand and contract; implosion of the bubbles causes localized intense heat and pressure liberation at the tip, resulting in emulsification of lens material. Continuous cavitation, produced by continuous ultrasound delivery, is less efficient than transient cavitation, produced by intermittent ultrasound delivery.
This undesirable phenomenon occurs when the repulsive force of the ultrasonic stroke overcomes the vacuum, or “holding power.” This process causes the nuclear fragments to be repelled by the ultrasonic tip until the vacuum reaches a level sufficient to neutralize this repulsive energy and once again hold the material. This back-and-forth movement of lens material from the tip impairs followability (see the Glossary of Fluidics and Phacodynamics Terminology). Chatter can be diminished by reducing the phaco power (ie, by decreasing the stroke length of the tip), thereby reducing the forces that push a fragment away from the tip.
The ratio of power-on time to total power-on plus power-off time. For example, a 10 millisecond pulse of phaco power followed by a 30 millisecond rest interval would have a duty cycle of 25%.
Power multiplied by time. Surgeons can reduce the amount of energy released inside the eye by decreasing either the phaco power or the length of time that the phaco power is on. Thus, energy and power are not the same.
The speed at which the phaco needle moves back and forth. The term ultrasonic is used for frequencies above the range of human audibility, or greater than 20,000 Hz. The frequency of phaco handpieces is between 27,000 and 60,000 Hz.
A type of transducer used in ultrasonic handpieces that transforms electrical energy into mechanical energy. Linear motion is generated when a tuned, highly refined crystal is deformed by the electrical energy supplied by the console.
The ability of the phaco needle to vibrate and cavitate the adjacent lens material. Power is noted as a linear percentage of the maximum stroke length of the phaco needle. Phaco power is produced when the foot pedal is in position 3.
The linear distance that the tip traverses to impact the lens material. Among phaco devices, the stroke length varies from 0.05 to 0.10 mm (or 0.002 to 0.004 inch).