Many resident surgeons find it challenging to learn the technique of phaco chop because of the force vectors which are required to split the nucleus. These specific maneuvers must be accomplished within a limited time frame of just a couple of seconds. The direction of force of the two hands changes during the chop.
(1) Once the phaco probe is embedded into the nucleus, the chopper is placed directly across from it and the two instruments are pushed towards each other. Note that the phaco probe may move a little bit, but most of the movement is the chopper being brought towards the phaco tip. Avoiding moving the nucleus — the phaco probe and chopper are doing the work while the lens nucleus stays relatively still.
(2) Continue to bring the chopper to the tip of the phaco probe. Even if the nucleus rotates, keep moving the two instruments directly towards each other. And remember that the nucleus still stays centered in the capsular bag with very little movement.
(3) Once the chopper is in close proximity to the phaco tip, the direction of the two instruments changes. The phaco probe and the chopper are then pushed apart. In this case, the chopper is brought towards the surgeon and the phaco probe is pushed away. This splits the nucleus by propagating the crack through the entire nucleus. Now two halves are created.
Click below to learn the direction of forces that are used in phaco chop: