Lens Nucleus Division and Fragmentation Techniques

Key Points at a Glance

Note

Nucleofractis Techniques

• General term for techniques to divide and remove the lens nucleus during phacoemulsification
• Representative techniques: Divide-and-Conquer, Phaco Chop, Stop-and-Chop
• Select technique based on nuclear hardness (Emery-Little Classification Grade I to V)
• Meta-analysis suggests phaco chop uses less ultrasound energy, shorter surgical time, and causes less corneal endothelial damage than divide-and-conquer¹⁾
• FLACS (femtosecond laser) pre-nuclear division is evolving as an adjunctive technique

Positioning of This Article

This article provides an overview of nucleus management techniques in cataract surgery. For detailed steps of individual techniques, refer to the articles on Stop-and-Chop and Vertical Chop.

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 techniques exist.

Dividing the nucleus into small fragments minimizes the amount of ultrasound energy used. This helps prevent damage to corneal endothelial cells and maintains postoperative visual acuity.

Nuclear hardness is generally classified using the Emery-Little Classification (Grade I to V).

Grade	Hardness	Appearance/Features
Grade I	Soft nucleus	Almost transparent, nucleus barely visible
Grade II	Slightly soft	Yellowish, slight opacity
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 representative technique was 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 (+) groove
3. Split the nucleus into four quadrants using two instruments
4. Emulsify and aspirate each quadrant

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

Phaco-Chop

This technique was devised by Nagahara (1993).

1. Insert and fixate the phaco tip into the nucleus
2. Advance the chopper under the lens capsule at the equator
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 irradiation, energy usage is low. It is particularly effective for hard nuclei (Grade III–V).

:::tip Choosing a 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

A hybrid technique devised by Koch (1994).

1. First, divide the nucleus into two using the divide-and-conquer method (stop)
2. Then, further fragment it 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 good for transitional learning stages.

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 cumulative dissipated energy (CDE) of MD −8.68 units (significant difference)¹⁾. However, there was no significant difference in surgical time, and surgeon proficiency must also be considered.

Vertical Chop

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

Soft Chop

A low-energy technique for soft nuclei (Grade I–II). It uses traction on the nucleus to mechanically divide it, minimizing 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 where the nucleus is prolapsed from the capsular bag into the anterior chamber or onto the iris plane for emulsification. May be used in cases with small pupils or weak zonules where intra-capsular manipulation is difficult.

Prechop / Phaco Prechop

A technique where the nucleus is mechanically split with a dedicated instrument before inserting the tip into the nucleus. Characterized by the ability to split the nucleus into 2–4 pieces without using any ultrasonic energy.

Femtosecond Laser-Assisted Cataract Surgery (FLACS)

Phaco surgery is performed after making the anterior capsulotomy, nuclear fragmentation, and corneal incisions 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, divide-and-conquer 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. Technique Selection by Nuclear Hardness

Soft to Moderately Hard Nuclei (Grade I–III)

Soft chop: Minimizes ultrasound usage

Divide-and-conquer: Easy to learn and safe

Stop and chop: Moderate difficulty, versatile

Hard nucleus / very hard nucleus (Grade IV–V)

Phaco chop: Mechanical division reduces energy use¹⁾

Vertical chop: Suitable 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 involving 837 patients.¹⁾

Parameter	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
Phacoemulsification time (PT)	−55.09 seconds	0.01	Phaco-chop superior
Total surgical time	No difference	0.18	Not significant

Phaco-chop has shown superiority in terms of ultrasonic energy and corneal endothelial protection. ¹⁾ However, no significant difference was found in total surgical 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 nuclear 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.

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

Both techniques share the same goal. That is, to safely remove fragmented nuclear pieces from the capsular bag while protecting the posterior capsule.

The most serious intraoperative complications are posterior capsule rupture and nuclear drop. Management of the movement path during emulsification and maintaining an appropriate distance from the posterior capsule are important.

7. Latest research and future perspectives

A 2024 meta-analysis reconfirmed that phaco-chop is superior to divide and conquer in terms of corneal endothelial protection and reduction of ultrasonic energy. ¹⁾

Future challenges include the following.

• Standardization of energy reduction effects of FLACS (femtosecond laser-assisted cataract surgery)
• Preoperative estimation of nuclear hardness and surgical technique selection support using artificial intelligence
• Expansion of safety margins through improvements in ultrasonic tip design and fluid dynamics systems

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

8. References

1. Guedes J, Pereira SF, Amaral DC, Hespanhol LC, Faneli AC, Oliveira RDC, Mora-Paez DJ, Fontes BM. Phaco-Chop versus Divide-and-Conquer in Patients Who Underwent Cataract Surgery: A Systematic Review and Meta-Analysis. Clin Ophthalmol. 2024;18:1535-1546. doi:10.2147/OPTH.S463525.
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.