Nucleus Division Techniques (Nucleofractis)

Key Points at a Glance

Note

Nucleofractis Techniques

• General term for procedures that divide and remove the lens nucleus using phacoemulsification.
• Representative techniques: Divide-and-Conquer, Phaco Chop, Stop-and-Chop
• Select the procedure according to nuclear hardness (Emery-Little classification Grade I–V)
• A meta-analysis has shown that phaco-chop uses less ultrasound energy, shorter surgical time, and causes less corneal endothelial damage compared to divide-and-conquer¹⁾
• FLACS (femtosecond laser) anterior nuclear division is developing as an auxiliary technique

Positioning of this article

This article is an overview of nucleus processing techniques in cataract surgery. For detailed steps of individual techniques, refer to the articles on stop-and-chop method and vertical chop method.

1. What is nucleofractis?

Phacoemulsification is the standard modern cataract surgery technique. Its core step is nucleofractis (division and fragmentation of the lens nucleus), for which several methods exist.

Dividing the nucleus into small fragments minimizes the amount of ultrasonic energy used. This prevents damage to corneal endothelial cells and helps maintain postoperative visual acuity.

The Emery-Little classification (Grade I to V) is generally used to classify nuclear hardness.

Grade	Hardness	Appearance/Features
Grade I	Soft nucleus	Almost transparent, nucleus barely visible
Grade II	Slightly soft	Yellowish, slightly cloudy
Grade III	Moderate	Yellow to amber
Grade IV	Hard nucleus	Amber to brown
Grade V	Very hard nucleus	Black, including Morgagnian degeneration

The higher the nuclear hardness, the more ultrasonic energy is required, increasing the burden on the corneal endothelium and posterior capsule.

2. Major Nucleus Division Techniques

Divide-and-Conquer

This is a representative technique devised by Gimbel (1991).

1. Create a crater in the center of the nucleus with the phaco tip.
2. Rotate the nucleus 90° at a time and carve a cross (+) shaped groove.
3. Divide the nucleus into 4 quadrants using 2 instruments
4. Emulsify and aspirate each quadrant

Suitable for moderately hard nuclei (Grade II–IV). Relatively easy to learn and considered a beginner-friendly technique.

Phaco-Chop

Technique developed by Nagahara (1993).

1. Insert and fixate the phaco tip into the nucleus
2. Insert the chopper under the equatorial lens capsule.
3. Separate the phaco tip and chopper to crack the nucleus.
4. Emulsify and aspirate while dividing the nucleus into small pieces.

Since the nucleus is mechanically divided before ultrasound application, energy usage is low. It is particularly effective for hard nuclei (Grade III–V).

:::tip Choosing the chopper Horizontal and vertical choppers differ in their angle of access to the nucleus. Select based on nucleus size, hardness, and anterior chamber depth. :::

Stop-and-Chop Technique

A hybrid technique devised by Koch (1994).

1. First, the nucleus is divided into two using the divide-and-conquer method (stop).
2. Then, it is further fragmented using the phaco-chop technique (chop).

This technique combines the advantages of divide-and-conquer and phaco-chop. It is suitable for moderate to hard nuclei and is also appropriate for use during the transitional learning phase.

Q Which is gentler on the cornea: phaco-chop or divide-and-conquer?

A

According to a meta-analysis, phaco-chop shows superior corneal endothelial protection compared to divide-and-conquer, with a mean difference in endothelial cell count of MD −221.67 cells/mm² (favoring phaco-chop) and a mean difference in cumulative dissipated energy (CDE) of MD −8.68 units (significant difference)¹⁾. However, there was no significant difference in surgical time, and the surgeon’s skill level must also be considered.

Vertical Chop

Technique devised by Akahoshi (around 1997). The phaco tip is inserted deep into the nucleus, and the nucleus is divided by vertical splitting. Suitable for cases with small pupils or shallow anterior chambers where there is limited space for horizontal insertion of the chopper.

Soft Chop

Low-energy technique for soft nuclei (Grade I–II). Mechanical division using traction on the nucleus minimizes ultrasound exposure.

3. Special and Advanced Techniques

Crater-and-Chop

A technique that combines chopping after creating a crater. Used for Grade IV–V very hard nuclei when chopping alone is difficult to divide.

Multilevel Chop

A technique that divides the nucleus stepwise at multiple depth levels. Enables safe management of large and very hard nuclei.

Supracapsular Techniques

A technique in which the nucleus is prolapsed from within the capsular bag into the anterior chamber or onto the iris plane for emulsification. May be used in cases of small pupils or zonular weakness where intra-bag manipulation is difficult.

Prechop / Phaco Prechop

A technique in which the nucleus is mechanically split using a dedicated instrument before the tip is inserted into the nucleus. It is characterized by the ability to split the nucleus into 2 to 4 pieces without using any ultrasonic energy.

Femtosecond Laser-Assisted Cataract Surgery (FLACS)

Phaco surgery is performed after anterior capsulotomy, nuclear fragmentation, and corneal incision are made with a femtosecond laser. Laser nuclear fragmentation is expected to reduce ultrasonic energy, but clinical differences from conventional surgery remain under debate.

Q Which technique is most suitable for beginners?

A

Generally, the divide-and-conquer technique is recommended for beginners. Each step is clear and easy to learn, and it can handle up to moderately hard nuclei. Phaco chop is more energy-efficient but requires skill to accurately insert the chopper under the equatorial capsule. The typical training progression is to first master divide-and-conquer, then move to stop-and-chop, and finally to phaco chop.

4. Selection of technique by nuclear hardness

Soft to moderate hardness (Grade I–III)

Soft chop: Minimizes ultrasound energy use

Divide and conquer: Easy to learn and highly safe

Stop and chop: Moderate difficulty, versatile

Hard to very hard (Grade IV–V)

Phaco chop: Mechanical division reduces energy ¹⁾

Vertical chop: For shallow anterior chamber or small pupil

Crater and chop: Stepwise approach for very hard nucleus

5. Phaco Chop vs Divide and Conquer: Evidence

A 2024 meta-analysis (Guedes et al.) compared 9 studies with 837 cases. ¹⁾

Outcome	Mean Difference (MD)	p value	Result
Corneal endothelial cell count	−221.67 cells/mm²	0.02	Phaco-chop superior
Cumulative dissipated energy (CDE)	−8.68 units	<0.01	Phaco-chop superior
Ultrasound time (UST)	−51.16 seconds	0.04	Phaco-chop superior
Phaco time (PT)	−55.09 seconds	0.01	Phaco-chop superior
Surgery time (total)	No difference	0.18	No significant difference

Phaco-chop showed superiority in terms of ultrasound energy and corneal endothelial protection. ¹⁾ However, no significant difference was observed in total surgery time. ¹⁾

:::caution Notes on surgical technique selection Phaco-chop is a technique that requires proficiency. Selection should be based on the surgeon’s experience, facility environment, and patient’s ocular conditions (anterior chamber depth, zonular status). Evidence is for reference only, and clinical judgment is necessary for application to individual cases. :::

6. Pathophysiology and Mechanics of Nucleus Division

The lens nucleus consists of the epinucleus and endonucleus. As nuclear hardness increases, protein cross-linking within the nucleus becomes denser and elasticity decreases.

The divide-and-conquer technique weakens the nucleus through thermal and mechanical effects of ultrasound before dividing it. Phaco-chop applies mechanical shear force first, reducing subsequent ultrasound energy.

The goal of both techniques is the same: to safely remove the fragmented nucleus from the capsular bag while protecting the posterior capsule.

The most serious intraoperative complications are posterior capsule rupture and nucleus drop. It is important to manage the movement path during emulsification and maintain an appropriate distance from the posterior capsule.

7. Latest Research and Future Perspectives

The superiority of phaco-chop over divide-and-conquer in corneal endothelial protection and ultrasound energy reduction has been reconfirmed in a 2024 meta-analysis. ¹⁾

Future challenges include the following.

• Standardization of energy reduction effect of FLACS (femtosecond laser-assisted)
• Preoperative estimation of nuclear hardness and procedure selection support using artificial intelligence
• Expansion of safety margins through improvements in ultrasound chip shape and hydrodynamic system

:::danger Disclaimer This article is a general explanation intended to provide medical information and does not recommend any specific surgical procedure. The actual surgical indications and procedure selection should be determined by the attending physician after evaluating the patient’s condition. :::

8. References

1. Guedes CM, Guedes VM, Chaoubah A. Phaco-Chop versus Divide-and-Conquer in Patients Who Underwent Cataract Surgery: A Systematic Review and Meta-Analysis. Clin Ophthalmol. 2024;18:1475-1487. doi:10.2147/OPTH.S458093
2. Wong T, Hingorani M, Lee V. Phacoemulsification time and power requirements in phaco chop and divide and conquer nucleofractis techniques. J Cataract Refract Surg. 2000;26(9):1374-8. PMID: 11020623.
3. Can I, Takmaz T, Genç I. Half-moon supracapsular nucleofractis phacoemulsification technique. Ophthalmic Surg Lasers Imaging. 2010;41(3):390-3. PMID: 20507027.