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Foot pedal control plays crucial role during phacoemulsification
To prevent the eye from collapsing, the pedal should be in the irrigation position before entering the eye with the phaco probe.
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During surgery we clearly need precise control of both hands to hold instruments and operate within the confines of the anterior segment. We also need to coordinate fine control of both feet, as they play a crucial role in controlling the foot pedals. The traditional placement is to have the microscope foot pedal controls for the left foot while the right foot controls the phaco foot pedal.
The primary microscope controls are focus, zoom and centration. Additional functions include the ability to turn the microscope light on and off as well as adjust the brightness. The microscope should be reset and centered at the beginning of the case in order to provide a full range of adjustability. Avoid high magnification for routine cases as this will unnecessarily limit your field of view.
 Uday Devgan |
The more important pedal during phacoemulsification is the phaco foot pedal as it controls the irrigation, aspiration and ultrasonic power delivery. Fine control of fluidics and power can be achieved with practice. The three positions of the phaco foot-pedal are: 1) irrigation, 2) aspiration and 3) ultrasound. Each step is additive, so when we are in position 2, we have irrigation plus aspiration, and in position 3, we have irrigation, aspiration and ultrasound power delivery.
The irrigation in position 1 is either on or off – there is no ability to titrate the amount of irrigation via the foot pedal. You will recall that the irrigation inflow is determined by the bottle height and the size of the inflow tubing. Taking the foot off the pedal completely is called position zero because the phaco probe is doing nothing.
The aspiration in position 2 can be controlled in a linear manner: The beginning of position 2 gives lower aspiration, and as you depress the pedal further into position 2, you get more and more aspiration. This is similar to the gas pedal on cars, where the acceleration is proportional to the amount of pedal depression.
Position 3 also has the ability for linear control, where progressively greater depression of the pedal gives more phaco energy. Depending on the type of phaco power modulation used, the foot pedal depression in position 3 will give more ultrasound energy. In phaco pulse mode, further depression increases stroke length of the phaco needle. In phaco burst mode, further depression increases the number of bursts per second by limiting the rest interval between bursts.
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| Images: Devgan U |
Foot pedal position during steps of surgery
Before entering the eye with the phaco probe, the foot pedal should be in position 1 so that the irrigation fluid will prevent the eye from collapsing. A soft nucleus could be removed with simple aspiration in position 2; however, any cataract with significant nuclear density will require ultrasound energy.
To emulsify the cataract, the phaco probe should deliver energy during the forward stroke. Then when retracting the phaco probe, there is no need to deliver energy, so we can go back to position 2 for aspiration or even position 1 for simple irrigation only.
Once we have a nuclear fragment or piece, we can use aspiration in foot position 2 to bring the piece to the tip in preparation for emulsification. Once the cataract piece is right at the phaco tip, application of ultrasound energy in position 3 will emulsify it.
The goal of modern cataract surgery is ultrasound-assisted aspiration of the lens, where the primary means of lens removal is the aspiration while the ultrasound phaco energy is only given to assist. This will allow us to minimize the amount of energy that is placed into the eye and will result in better outcomes.
Accurate foot pedal control requires patience to master, but once learned, it allows an increased margin of safety and efficiency during phacoemulsification.
For more information:
- Uday Devgan, MD, FACS, is in private practice at Devgan Eye Surgery in Los Angeles, Beverly Hills, and Newport Beach, California. Dr. Devgan is Chief of Ophthalmology at Olive View UCLA Medical Center and an Associate Clinical Professor at the Jules Stein Eye Institute at the UCLA School of Medicine. Dr. Devgan can be reached at 11600 Wilshire Blvd., Suite 200, Los Angeles, CA 90025; 800-337-1969; fax: 310-388-3028; e-mail: devgan@gmail.com; Web site: www.DevganEye.com. Dr.Devgan is a consultant to Abbott Medical Optics and Bausch & Lomb, and is a stockholder in Alcon Laboratories and formerly in Advanced Medical Optics.