The Phacoemulsification Platform
All phacoemulsification (phaco) platforms share the same basic structure and concepts. The phaco machine aims to balance fluidics within the eye, while delivering ultrasonic energy and vacuum in order to emulsify and aspirate the cataract through a small incision.
The main functions of the phaco machine are to provide irrigation into the eye; to create vacuum/aspiration to remove the cataract; and to deliver ultrasound energy in order to emulsify the nucleus. These functions correspond to the machine’s 3 foot pedal positions (Figure 1).
Foot Position 1: Irrigation
The irrigation function of the phacoemulsification machine provides a source of fluid infusion into the eye during the surgery. Depressing the foot pedal to position 1 turns on the infusion. There is no linear control of the infusion—the infusion is either turned on or turned off. The height of the infusion bottle determines the relative infusion pressure and flow rate during the surgery. To keep the eye inflated during surgery, the surgeon needs to make sure that the fluid inflow rate is at least as great as the fluid outflow rate, because any excess inflow will pressurize the eye and leak from the incisions until equilibrium is achieved. An optional switch for continuous flow is available and is useful in avoiding inadvertent release of position 1 and potential collapse of the anterior chamber.
Foot Position 2: Vacuum and Aspiration of Fluid
Position 2 controls the vacuum and the relative aspiration rate of the fluid from the eye. There may be a linear control of vacuum and flow, so that the top of position 2 provides less vacuum or flow than the middle or bottom range of the pedal. This is similar to the gas pedal in a car, where the car’s throttle opens more as the gas pedal is further depressed. The vacuum and aspiration levels created during surgery draw the fluid out of the eye and into a waste fluid collection via the outflow tubing.
Foot Position 3: Ultrasound Energy
Position 3 controls the delivery of ultrasound energy. There is linear control of the ultrasound energy level so that further pedal depression results in more ultrasound energy. Note that if the pedal is in position 3, the surgeon is already engaging the full function of both positions 1 and 2. The irrigation is on, and the vacuum and aspiration level is at its highest preset level. Ultrasound energy should only be applied once the tip of the phaco probe is in contact with part of the cataract.