When Dr. Nagahara introduced the phaco chop technique 25 years ago, it improved cataract surgery dramatically. Total ultrasound energy was reduced, surgery was more efficient, and safety improved. There did remain one challenge, however, and that is the steep learning curve for this technique. With direct mentoring, most of my resident ophthalmologists over the past two decades have been able to learn phaco chop and become adept with the technique. For an experienced surgeon, access to hands-on teaching is difficult, and most revert back to the divide-and-conquer technique that works sufficiently well in their hands. By combining the advantages of the horizontal and vertical chop techniques, we can simplify the learning process and allow more surgeons to upgrade to this method of nucleus disassembly.
Horizontal vs. vertical chop
The idea behind the chop technique is to use a mechanical device, the phaco chopper instrument, to divide the nucleus into halves and then smaller fragments that are more easily phacoemulsified from the eye. The standard divide-and-conquer technique requires using ultrasound energy to first sculpt grooves into the nucleus, which can then be cracked into smaller pieces. The two primary advantages of phaco chop are reduced ultrasound energy and increased efficiency. Chop techniques require the phaco probe to securely hold the nucleus and prevent it from moving as the chopper splits the cataract.
In the horizontal technique, the chopper is placed under the capsulorrhexis edge and around the equator of the nucleus. The resultant cleavage plane is propagated horizontally, hence the name. In vertical chopping, the tip of the chopper is embedded into the central nucleus along with the phaco probe and the cleavage plane is propagated vertically from anterior to posterior. The hesitation for many surgeons learning horizontal chop is placing the chopper under the capsulorrhexis edge and then moving it toward the lens equator without direct visualization. The limitation of the vertical chop technique is that it works better in a dense nucleus and typically requires a sharp-tipped instrument.
The combo-chop
Combining the best of the horizontal and vertical chop techniques allows us to avoid going under the capsulorrhexis edge and permits the use of a standard chopper with a blunt tip. The first step in the cataract surgery is to make a sufficiently large capsulorrhexis in order to allow us to bring one half of the nucleus out of the capsular bag after the first chop has been accomplished. We are aiming for a 5-mm diameter, and this is facilitated by using forceps that have 2.5-mm and 5-mm marks from the tip of the instrument, allowing instant measurement of both the radius (2.5 mm) and diameter (5 mm) of the capsulorrhexis (Figure 1a).
After gentle but complete hydrodissection, the phaco probe must be buried into the nucleus in order to fixate it (Figure 1b). The vacuum setting should be high, at least 400 mm Hg, and the probe should be placed just inside the subincisional capsulorrhexis. This is a critical step because if the phaco probe is placed in the center of the nucleus, then there will not be sufficient propagation of the chop. The chopper tip is now embedded into the nucleus within the confines of the nasal edge of the capsulorrhexis (Figure 1c). Now both instruments are brought together to start a horizontal chop, and then the force vector changes 90° and they are pushed apart to finish the vertical chop (Figure 1d).
This chop has created a cleavage plane that divides the nucleus into two halves while keeping both instruments within the central 5 mm of the nucleus, within the capsulorrhexis. In this case, the dense, fibrous cataract is separated into the two nuclear halves by pushing the instruments apart (Figure 2e). The first half of the nucleus is then impaled with the phaco probe using high vacuum, and it is brought out of the capsular bag into the iris plane where it is sub-chopped into smaller fragments that are then phaco-aspirated (Figure 2f). The same is done for the second nuclear half (Figure 2g), and the complete nucleus removal, even in this dense cataract, is accomplished in 2 minutes with a minimal amount of ultrasonic energy. More routine cataracts can be removed in about 1 minute with even less phaco energy. After IOL insertion, it is confirmed that the capsulorrhexis is 5 mm in diameter and fully overlaps the 6-mm optic (Figure 2h).
This combo-chop technique combines the best of the horizontal and vertical chop methods to allow safe and efficient nucleus removal during cataract surgery. A full video of this cataract surgery can be seen at www.CataractCoach.com.