DIVIDE AND CONQUER

The divide and conquer technique of nucleofractis is the basic technique that every phaco surgeon starts their training with. It is essentially ideal for denser nuclei and is not suitable for soft nuclei where the probe may punch a hole in the capsule before the surgeon can react.

SCULPTING

Once the nucleus rotates freely, a pair of cross-grooves are created in the nucleus. Sculpting is started with moderate flow, low vacuum and continuous ultrasound power. Power used is based on nuclear density. Hard nuclei need higher power as insufficient power causes the phaco probe to push the nucleus forwards with resultant zonular stress.

Higher vacuum levels, on the other hand, can cause the nucleus to stick to the phaco tip and may inhibit smooth movement of the tip through the nucleus. During superficial grooving, sculpting should be stopped short of the rhexis to avoid accidental damage to the rhexis rim and the anterior capsule. Subsequent grooves are taken beyond the rhexis rim. During each sculpting motion, the morphology of the lens should be kept in mind and downslope sculpting initially should be followed by upslope sculpting beyond the centre of the nucleus.

Following the curve of the posterior capsule (PC) in this manner gets an even trench through its length while also avoiding accidental perforation of the PC. Ultrasound power should be used only during forward movement of the tip and the foot pedal should return to position 1 during the reverse movement. Once a sufficiently deep trench is created, the nucleus is rotated 180 degrees and the trench is lengthened as well as deepened in the other hemi-nucleus. A clear red reflex in comparison to the rest of the nucleus indicates a satisfactory depth to the trench.

However, as newer microscopes have excellent coaxial illumination, the red reflex is generally bright from the beginning of the surgery even in dense nuclei and this sign may not be absolutely depended on. The thickness of the adult lens is about 4-5mm and the phaco tip is slightly less than 1mm.

Another important indicator for adequacy of depth is therefore an approximate three phaco tips deep groove which leaves a thin enough posterior plate which is easy to crack. The width of the groove is kept at about one and a half phaco tips width, to allow two instruments to go down into the depth of the trench for cracking the posterior plate. Once the first groove is created, the second groove is made at 90 degrees to the first. The nucleus may also be rotated by 90 degrees at a time to create and deepen the cross grooves.

NUCLEAR ROTATION

A longer lever arm eases rotation. Less force is required when the instrument is placed in the peripheral groove rather than in the centre. Rotating closer to the centre results in application of more force and consequent increased stress on zonules.

CRACKING

Once both grooves are created, the nucleus is cracked into four quadrants. This is done either by conventional cracking or cross cracking. Conventional cracking is preferable when main and side port incisions are placed at acute angles or at less than 90 degrees to each other, whereas cross cracking is preferable with incisions that are at 90 degrees to each other. The crack is initiated at the distal end and widened towards the proximal end. Once the crack has gone full thickness, the nucleus is rotated to complete the crack through the opposite end. This is repeated for the second groove in order to divide the nucleus into four quadrants. While cracking, the two instruments should be kept in the depth of the groove and the quadrants separated with a slight upward motion. The natural tendency to push downwards can lead to zonular stress and should be avoided.

QUADRANT REMOVAL

Settings are now changed to a higher vacuum and pulse or hyperpulse phaco. The first quadrant is generally more difficult to extract as the pieces are aligned together as in a jigsaw puzzle. Once the first quadrant is removed, the remaining quadrants are no longer packed as tightly together and subsequent ones are easier to remove. Quadrants are embedded at the tip at mid-depth in foot position 3, and once the tip is adequately buried the piece is gently manoeuvred into the anterior chamber with foot pedal position 2.

COMPLICATIONS

Not performing upslope sculpting beyond the midpoint of the lens can cause the nucleus to rupture the PC. Not performing downslope sculpting ahead of the midpoint can leave a thick posterior plate which prevents the crack from propagating. Using insufficient power while sculpting can push the nucelus and cause zonular stress. Inability to crack the nucleus can result from the groove not being deep enough, leaving behind a thick posterior plate or because the forces are not applied in the right manner. Cracking may also be difficult if the instruments haven’t been placed deep enough in the groove. Zonular dialysis and nucleus drop may occur if excessive posteriorly directed force is applied while grooving or cracking. Not maintaining the cruciate shape of the grooves can result in a large central crater with dense walls that becomes difficult to disassemble. The width of the groove should therefore be limited to one and a half phaco tips.

ADVANTAGES AND DISADVANTAGES

The divide and conquer technique is the basic technique learned by the beginner surgeon. It is easy, effective and breaks the nucleus into smaller quadrants that are more easy to manage. It can be used effectively in denser nuclei as well and can help decrease the amount of phaco energy at the endothelial level. It is difficult to perform in soft nuclei as the tip eats through the nucleus very fast and the two instruments cheesewire through the quadrants on attempting a crack.