The vertical chop technique is one of the nuclear division methods in phacoemulsification. It is also called the “karate chop” technique.
Chop techniques are broadly divided into two types: “horizontal chop” and “vertical chop.” The horizontal chop technique was first reported by Dr. Kunihiro Nagahara in 1993 (ASCRS Seattle Annual Meeting), where the ultrasonic tip and chopper are brought toward each other on a horizontal plane to divide the nucleus. The vertical chop technique differs in that the chopping motion is performed on a vertical plane.
The phaco chop technique was devised by Nagahara et al. in 1993. Compared to the divide and conquer (D&C) technique, it reduces ultrasonic time and improves surgical efficiency, and has become widely adopted worldwide.
The main advantage of the chop technique is that nuclear division is achieved primarily by manual instrument force rather than ultrasonic energy, thereby reducing total energy load.
In the horizontal chop technique (so-called phaco chop), the chopper is inserted under the anterior capsule from the continuous curvilinear capsulorhexis edge, placed at the equator, and moved horizontally toward the US tip. In the vertical chop technique (karate chop), the chopper is not inserted under the continuous curvilinear capsulorhexis; instead, it is inserted vertically from inside the continuous curvilinear capsulorhexis near the center of the anterior lens surface to split the nucleus. Therefore, the vertical chop technique has a lower risk of capsular damage, and the procedure is completed entirely within the continuous curvilinear capsulorhexis.
Since this section describes cataract surgery techniques, the “main symptoms” include general cataract findings and characteristic intraoperative findings.
Good Indications
Hard nucleus (Grade 4–5): A sharp chopper can easily penetrate the hard nucleus, allowing efficient division.
Weak zonules: Minimal stress on zonules during continuous curvilinear capsulorhexis.
Small pupil: The chopper tip can be operated while always visible in the surgical field.
Capsulorhexis extension cases: Reduces risk of further extension compared to horizontal chop.
Contraindications
Very soft nucleus: Posterior subcapsular cataract (PSC), refractive lens exchange (RLE).
Issues with soft nucleus: Sharp chopper cannot efficiently split soft nucleus, increasing risk of capsular damage.
Alternative technique: The flip method or horizontal chop method is recommended.
Vertical chop is a surgical technique, not a disease itself. The following describes situations requiring this technique and associated risk factors.
The development of dense cataract involves the following:
Causes of weak zonules include pseudoexfoliation syndrome, Marfan syndrome, trauma, high myopia, and advanced age.
This section describes preoperative evaluation of cataracts.
Observation of nuclear color and opacity pattern using a slit-lamp microscope is fundamental. It is evaluated on a scale of Grade 1 to 5 according to the Emery-Little classification.
| Grade | Slit-lamp Findings | Nuclear Hardness |
|---|---|---|
| 1–2 | Clear to white/yellow-white | Soft to moderately soft |
| 3 | Yellow | Moderate |
| 4–5 | Yellowish-brown to brown | Hard to extremely hard |
Multiple studies have shown that phaco chop is the most efficient technique for hard nuclei (Grade 4–5) cataracts and causes less damage to the corneal endothelium.
The initial stage is the same as standard phacoemulsification.
Steps specific to the vertical chop technique:
A representative instrument is the Koch-Nagahara Karate Chopper by Katena. This chopper features a sharp chopper on one end and a flat spatula on the other.
In the horizontal chop technique, a blunt paddle-shaped chopper must be slid under the capsule to “hook” the lens equator. This maneuver may cause the following issues.
The vertical chop technique solves this problem as follows.
Lens fibers have a lamellar orientation. The chopping method mechanically fractures along this natural structure, allowing more efficient nuclear division than indiscriminate use of ultrasonic energy.
In femtosecond laser-assisted cataract surgery (FLACS), mechanical nuclear division can be performed with a laser. This is expected to further reduce ultrasonic energy, but research is ongoing to determine whether it shows a significant advantage over conventional manual chopping techniques.
With the spread of micro-incision cataract surgery (MICS), the application of the vertical chop technique using smaller instruments is being investigated. Small incisions help reduce postoperative astigmatism and improve wound stability, but they also limit the operating space.
In developing regions where many patients present with advanced cataracts, the vertical chop technique is considered particularly useful as a versatile procedure capable of handling hard nuclei. Educational and dissemination activities from this perspective are also attracting attention.
