The stop-and-chop technique is one of the nuclear processing methods in phacoemulsification (PEA). It was reported by Koch PS and Katzen LE in 1994.
In the history of nuclear emulsification techniques in phacoemulsification, until the 1980s, a single method that gradually shaved the nucleus from the surface was used. In the 1990s, safe and efficient two-handed division methods were developed, and modern phacoemulsification has evolved with D&C and phaco chop as two major schools. Stop-and-chop emerged in 1994 as a bridge between the two, and along with D&C and phaco chop, it has become one of the most popular techniques in phacoemulsification.
The lineage of phacoemulsification techniques is shown below.
| Technique | Developer | Year of development |
|---|---|---|
| D&C | Gimbel | 1991 |
| Phaco chop | Nagahara | 1993 |
| Stop & Chop | Koch | 1994 |
| Semi-Crater & Split | Soda/Yaguchi | 2015 |
Currently, after mastering basic techniques in D&C, many surgeons transition to stop-and-chop or phaco-chop.
This method is recommended as a step for beginners to learn chopping techniques after mastering basic operations such as grooving, dividing, nucleus rotation, and fragment removal in D&C. It is highly versatile and serves as a gradual stepping stone for learning.
This section is an explanatory article on surgical techniques; patient symptoms are the same as those for general cataracts.
The following shows the state of the lens nucleus that the surgeon should assess preoperatively. Nuclear hardness directly affects the choice of surgical technique.
Indications for Stop-and-Chop
Soft nucleus (grade 1–2): Easy to manipulate. Phaco chop is also sufficient.
Moderate nucleus (grade 3): The most typical indication for this technique. Highly versatile.
Hard nucleus (grade 4): This technique can also handle it, but phaco chop is more efficient.
Unsuitable or difficult nuclei
Extremely soft nucleus: Groove creation is difficult and unsuitable.
Black-brown extremely hard nucleus: Consider crater-and-chop or extracapsular cataract extraction.
Zonular weakness: Care is needed during nuclear rotation.
The stop-and-chop technique has the following risk factors related to surgical difficulty:
The preoperative evaluation for appropriate selection of the stop-and-chop technique is shown below.
Observe the color and opacity of the nucleus using a slit lamp microscope. Evaluate using the Emery-Little classification (grades 1–5) or the Buratto classification to determine the surgical technique. The following table shows the relationship between nuclear color and hardness.
| Nuclear Color | Hardness Range | Example Recommended Technique |
|---|---|---|
| Light brown | Center only | D&C, phaco chop |
| Light brown | Center and periphery | Stop and chop |
| Dark brown | Center and periphery | Crater and chop |
| Black | Entire | Consideration for extracapsular cataract extraction |
The step-by-step surgical procedure of the stop-and-chop technique is described.
A report comparing D&C, stop-and-chop, and phaco-chop techniques found that for Emery-Little grade 4 (hard nucleus), phaco-chop resulted in significantly shorter ultrasound time, lower cumulative energy, less BSS (balanced salt solution) use, and a significantly lower corneal endothelial cell loss rate 2). For mild to moderate cataracts, all three techniques were effective 2)3). Phaco-chop uses less US power and emulsifies the nucleus most efficiently, making it, along with stop-and-chop, the most popular technique 3).
In D&C, because the first two splits are performed reliably, the cross-section of the nucleus can be grasped during subsequent chopping, making the operation easier. Phaco-chop requires the skill to reliably split the nucleus in two with the first strike, but this method avoids that difficulty. It is also useful as a step for beginners to learn chopping techniques.
In nuclear management during cataract surgery, thermal damage from ultrasonic energy and the impact of mechanical manipulation on corneal endothelial cells are concerns. The higher the efficiency of nuclear division, the less ultrasonic energy is used, minimizing the impact on the corneal endothelium and intraocular tissues.
In the stop-and-chop method:
Combining D&C and phaco-chop leverages the advantages of both techniques, achieving reliable division through grooving and efficient nuclear processing through subsequent chopping.
Nuclear hardness may differ between the center and periphery. In cases with a strongly brown nucleus, the periphery is often hardened as well, making complete division difficult with a single chop using phaco-chop alone. In stop-and-chop, grooving exposes the cross-section of the nucleus, allowing reliable division by applying the tip to that cross-section.
An approach combining incision size reduction (2.2 mm or less) with the stop-and-chop technique is being investigated. Small incisions improve anterior chamber stability, but the limited operating space restricts chopper movement, posing a challenge.
In the method where a femtosecond laser is used to create a preliminary capsulotomy or segmentation grooves before phacoemulsification, a reduction in ultrasonic energy is expected. By replacing the first half (groove creation) of the conventional stop-and-chop technique with a laser, it has been suggested that the impact on the corneal endothelium can be further reduced.
