'Non-stop' Phaco Chop

a SLACK Incorporated newspaper

Dr. Chang is an Associate Clinical Professor of Ophthalmology at the University of California, San Francisco. He has been in private practice in Los Altos, California since 1984.

by David F. Chang, MD

As with Dr. Nagahara's original technique, non-stop phaco chop begins with a single, deep chop down the middle - splitting the nucleus completely in half without any shaving or grooving. I have always used the blunt Lieberman microfinger as a chopper. After slight rotation, the second chop creates a small pie-shaped piece which is then manually tumbled out of the bag with the microfinger. The microfinger's long, curved tip is ideally shaped for slipping beneath the anterior capsule and around the equator.

The subsequently chopped pieces can then either be manually pulled out with the microfinger or aspirated out with the phaco tip. Just as with a pie or a cake in a box, the second piece is much easier to remove than the first because of the newly vacated adjacent space.

By eliminating shaving, chopping minimizes phaco power and time. Manual energy, generated by the chopper pushing centrally against the phaco tip, replaces the need for ultrasound energy to subdivide the nucleus. Ultrasound is only necessary in the aspiration of the large nuclear pieces. Although non-stop phaco chop is my standard technique, it provides advantages in dealing with the complicated cases.

Non-stop phaco chop is ideal with small pupils because the phaco tip never moves peripheral to the central 3 mm of the pupil. Eliminating the initial groove completely avoids having to perform any phaco blindly behind the iris. With small pupils, the intensity of the red reflux is significantly reduced, making it difficult to judge one's depth within the nucleus. This is a problem for cracking techniques, which require a long and adequately deep central trough. Phaco chop, however, is more tactile, and kinesthetic, and less dependent on visualizing the phaco tip within the nucleus.

Hypermature cataracts present several different problems. The complete lack of a red reflex makes it difficult both to perform a capsulorhexis and to judge one's depth within the nucleus. These nuclei are often very hard and brunescent and as such, most readily transmit the forces of phacoemulsification and manipulations such as shaving, cracking, and rotation directly to the zonules and to the capsule.

Phaco chop reduces stress on the zonules. Ultrasound energy is replaced by manual energy, generated by one instrument pushing against the other, and all of the forces are directed centrally inward rather than outward toward the capsule and the zonules. The combined reduction in phaco power, phaco time, and zonular stress that chopping af chopping, it is the phaco tip and high vacuum which hold and fixate the nucleus against the force of the chopper.

Because of the forces being directed inwardly and centripetally, phaco chop is the procedure of choice anytime there is either a can opener capsulotomy, or an incomplete capsulorhexis with a single radial tear. In these cases, repeated outward cracking motions would risk extending anterior capsule tears into the posterior capsule.

Loose zonules may be present in patients with exfoliation, traumatic cataracts, advanced age, retinopathy of prematurity, and prior eye surgery. These fragile zonules will easily dehisce with any forces placed on the capsule. Nonstop phaco chop minimizes stress on the zonules by replacing shaving and cracking maneuvers with inwardly directed manual chopping forces.

With pure chopping techniques, the pie-shaped pieces of nucleus fit tightly inside the capsular bag, like pieces in a wooden jigsaw puzzle. To solve this problem, Dr. Paul Koch's stop-and-chop technique begins with a wide and deep central trough. This allows the nucleus to be cracked in half and an initial working space created so that subsequently chopped pieces can be maneuvered out with the phaco tip. However, a significant amount of ultrasonic energy and zonular stress is generated during the sculpting of the initial groove.

By contrast, the keys to non-stop phaco chop in a firm nucleus are 1) to make the initial chop deep enough to split the nucleus in half, 2) to make the first piece very small, and 3) to manually pry out the first piece with a microfinger.

In conclusion, non-stop phaco chop decreases phaco time and energy, decreases stress on the zonules and capsule, and confines all of the phacoemulsification to the central 3 mm of the pupil. It is, therefore, of particular advantage in complicated cases that carry an increased risk of posterior capsule rupture.