CHOO CHOO CHOP AND FLIP

TECHNIQUE

Choo choo chop and flip phaco is a technique designed to take advantage of the power modulations and control as well as the improved fluidics of modern phaco technology.

After clear corneal incision, cortical cleaving hydrodissection followed by hydrodelineation is performed. After the two hydro steps, the nucleus should rotate easily within the capsular bag. The 30-degree phaco tip is introduced bevel down to aspirate the epinucleus uncovered by the capsulorrhexis. For the superficial epinucleus as well as the chopping, low vacuum settings are utilized. The Fine/Nagahara chopper (Rhein Medical, Tampa, FL) is placed in the golden ring and is used to stabilize the nucleus by lifting and pulling toward the incision slightly (Fig. 12–1), after which the phaco tip lollipops the nucleus in either low pulse mode at 2 to 4 pulses per second or burst mode. The technique is remarkably efficient. This efficiency is achieved because the decrease in cavitational energy around the tip at this low pulse rate or burst mode allows the creation of a tunnel in the nucleus in which the tip is embedded and fits the needle very tightly. This produces an excellent hold on the nucleus. With the energy set in this way, the ultrasonic energy delivered into the eye is minimized while the hold on the nucleus is maximized.

The Fine/Nagahara chop instrument is grooved on the horizontal arm close to the vertical chop element, with the groove parallel to the direction of the sharp edge of the vertical element. In scoring the nucleus, the instrument is always moved in the direc-

90 tion the sharp edge of the wedge-shaped vertical ele-

ment is facing (as indicated by the groove on the instrument), thus facilitating scoring. The nucleus is scored by bringing the chop instrument to the side of the phaco needle. It is chopped in half by pulling the chopper to the left and slightly down while moving the phaco needle, still in foot position 2, to the right and slightly up. Then the nuclear complex is rotated. The chop instrument is again brought into the golden ring (Fig. 12–2), and the nucleus is again lollipopped, scored, and chopped, with the resulting pie-shaped segment now lollipopped on the phaco tip (Fig. 12–3). The segment is then evacuated, using high vacuum and short bursts or pulse mode phaco at 2 pulses per second. The nucleus is continually rotated so that the pie-shaped segments can be scored, chopped, and removed essentially by the high vacuum assisted by short bursts or pulses of phaco. The short bursts or pulses of ultrasound energy continuously reshape the pie-shaped segments that are kept at the tip, allowing for occlusion and extraction by the vacuum. The size of the pie-shaped segments is customized to the density of the nucleus, with smaller segments for denser nuclei. Phaco in burst mode or at this low pulse rate sounds like “choo- choo-choo-choo”; hence, the name of this technique. With burst mode or the low pulse rate, the nuclear material tends to stay at the tip rather than chatter as the vacuum holds between pulses. The chop instrument is used to stuff the segment into the tip or keep it down in the epinuclear shell.

After evacuation of the first heminucleus, the second heminucleus is rotated to the distal portion of the bag, and the chop instrument stabilizes it while it is lollipopped. It is then scored and chopped. The

pie-shaped segments can be chopped a second time to reduce their size if they appear too large to easily evacuate.

After evacuation of all endonuclear material, the epinuclear rim is trimmed in each of three quadrants, mobilizing cortex as well in the following way. As each quadrant of the epinuclear rim is rotated distally and trimmed, the cortex in the adjacent capsular fornix flows over the floor of the epinucleus and into the phaco tip. Then the floor is pushed back to keep the bag on stretch until three of the four quadrants of epinuclear rim and forniceal cortex have been evacuated. It is important not to allow the epinucleus to flip too early, thus avoiding a large

FIGURE 12–1 Stabilization of the nucleus during lollipopping for the initial chop. Note the chopper at the hydrodelineation line and the nucleus drawn toward the incision.

amount of residual cortex remaining after evacuation of the epinucleus.

The epinuclear rim of the fourth quadrant is then used as a handle to flip the epinucleus (Fig. 12–4). As the remaining portion of the epinuclear floor and rim is evacuated from the eye, 80 to 90% of the time all of the cortex is evacuated with it.

Viscoelastic is replaced within the anterior segment, and intraocular lens (IOL) implantation is accomplished. With the IOL in place, simultaneous with viscoelastic removal, residual cortex is aspirated. Thus, the IOL is used as a barrier between the irrigation and aspiration (I&A) tip and the posterior capsule, minimizing the risk of posterior capsular tears during I&A.1

ANTERIOR CAPSULAR TEARS

If the chopper is placed too peripherally and the anterior capsular edge is not well visualized, it is possible to tear the anterior capsule or tear the zonules as the chopper is brought down for the chop. This problem is easily avoided. The chopper should be placed in the center of the nucleus with its tip touching the nucleus. It is then moved peripherally always in contact with the nucleus. It will reflect the anterior capsular edge and drop into the space created by hydrodelineation. As long as the chopper is in contact with the nucleus it will reflect the anterior capsule and slide beneath it,

FIGURE 12–3 Pie-shaped quadrant adherent to phaco tip after completion of the second chop. The phaco chopper can be used to stabilize and provide counter fixation for lollipopping the pie-shaped segment.

even if the edge of the capsulorrhexis cannot be visualized (Fig. 12–5). This process is facilitated by drawing the phaco tip, on top of the nucleus, toward the incision. This effectively moves the entire nucleus and with it the hydrodelineation line toward the incision so that the chopper does not have to go as far peripherally (Fig. 12–1).

INCOMPLETE CHOPS

It is important, during the chopping maneuver, to separate the instruments both vertically and hori-

FIGURE 12–5 The chopper is slid over the nucleus and reflects the edge of the anterior capsule.

zontally. Without the vertical component it is possible to make incomplete chops, essentially removing facets but leaving the posterior plate intact. The posterior plate may be firm, creating difficulty later in the procedure when it must be mobilized. If this should occur, the plate can be mobilized by gentle viscodissection below it. This will elevate it to the plane of the iris, away from the posterior capsule, where it can be easily chopped. Under no circumstances should bevel-down or bevel-up phaco with high vacuum be attempted. With the proximity of the plate to the posterior capsule the likely result will be to phaco through the plate and posterior capsule with instant rupture of the vitreous face!

SEGMENT MOBILIZATION

It is important to rotate segments to the distal portion of the capsular bag for mobilization and removal. Attempting to phaco the subincisional nucleus in the subincisional position carries a high likelihood of capsular rupture. Once a segment has been rotated, it should be grasped with vacuum and flow and drawn to the mid-pupil space before phaco power is applied. This seemingly simple principle will prevent inadvertent phaco through the equatorial bag.

CORTEX MOBILIZATION

It is important to perform adequate cortical cleaving hydrodissection to lyse nuclear-cortical-bag attachments for efficient cortex removal (see Chapter 7). It is also important to trim the epinuclear rim in three quadrants. The cortex can be seen to flow around the floor of the epinucleus in this process. Finally, when the last piece of epinucleus rim is aspirated it should be used as a handle to pull the epinucleus proximally. The second instrument can assist the process by pushing the epinucleus toward the peripheral equator. In this way the epinucleus and residual attached cortex are mobilized and aspirated at the pupillary plane.

If it is difficult to mobilize epinucleus, or if viscodissection of cortex is necessary, a dispersive viscoelastic is required as cohesive viscoelastic does not generate enough adhesive properties to drag the cortex to the periphery of the bag.

PHACO ENERGY APPLICATION

In an effort to focus cavitational energy into the nucleus, the bevel-down phaco tip should be maintained at the level of the anterior capsule for quadrant removal. It is used to mobilize nuclear material from above, rather than from below as is done in bevel-up techniques.

Additionally, the second instrument is used to feed nuclear material into the phaco tip. This will result in decreased amounts of energy being delivered to the anterior segment.

Finally, avoid chasing nuclear pieces or hurrying the procedure. Let the vacuum and flow settings bring material to the phaco tip. Then use power modulations to minimize chatter and maximize efficient emulsification of the fragment.

REFERENCE

1.Fine IH. The choo-choo chop and flip phacoemulsification technique. Oper Tech Cataract Refract Surg 1998;1:61–65.