Viscodivision Technique: Hydrodynamic Nucleus Cleavage and Posterior Capsule Protection in Femtosecond Laser-Assisted Cataract Surgery (FLACS)
In Femtosecond Laser-Assisted Cataract Surgery (FLACS), the laser platform performs capsulotomy and nuclear fragmentation in seconds. However, dividing the laser-fragmented nucleus inside the eye remains a significant challenge for many novice cataract surgeons.
The Viscodivision Technique, developed by ophthalmologist Dr. Alexander Chen (陳冠博醫師), utilizes the hydraulic force and spatial tamponade of dispersive ophthalmic viscosurgical devices (OVD) to achieve a complete “through-and-through crack” across the laser-cleaved nuclear quadrants. By dynamically delivering dispersive OVD through a 27G cannula into the laser cleavage planes, this technique eliminates instrument overmanipulation, avoids unnecessary ultrasound energy consumption, and provides a viscoelastic cushion over the posterior capsule.
💡1. The Energy Paradox and Clinical Dilemma in FLACS
The primary clinical objective of FLACS is to minimize Cumulative Dissipated Energy (CDE), thereby preserving corneal endothelial cell density. However, surgeons frequently encounter mechanical bottlenecks during nuclear division:
【The FLACS Nucleus Fragmentation Bottleneck】
- Laser Pre-cut leaves a 300–500μm Posterior Safety Margin
- Novice Surgeons Fail to Crack the Base Using Chopper
- Novice Surgeons Revert to Phaco Sculpting (Defeating FLACS Purpose)
- Excessive Manipulation, Thermal Energy Exposure, & Capsule Rupture Risk
- The 300–500 um Posterior Safety Margin:
- To safeguard against inadvertent posterior capsule perforation during laser delivery, all commercial FLACS systems deliberately leave an uncut 300-500 um safety margin at the bottom of the crystalline lens. This uncut nuclear layer—the posterior plate—often resists blunt mechanical cracking with conventional phaco choppers if not done correctly.
- The Ultrasound Sculpting Pitfall:
- Unable to split the quadrants cleanly, some surgeons revert to traditional “Divide and Conquer” maneuvers, using the phaco tip to groove and widen the pre-existing laser incisions. This unnecessary ultrasound sculpting defeats the primary purpose of using a femtosecond laser.
- Zonular Stress and Instrument Overmanipulation:
- Forcing mechanical choppers against an intact posterior plate generates lateral shear stress on fragile zonular fibers and increases the risk of sharp instrument tips puncturing the posterior capsule.
💡2. Biomechanical Principle of Viscodivision
The core philosophy of the Viscodivision Technique is straightforward: replace mechanical force with controlled hydraulic cleavage, and replace ultrasound groove-sculpting with viscoelastic space creation.
Using a dispersive OVD (such as Viscoat) mounted on a standard 27G blunt cannula, the surgeon engages the laser pre-cut cleavage plane. By dynamically injecting OVD while advancing the cannula deeper, the high-viscosity fluid acts as a hydraulic wedge. The fluid tracks along the path of least resistance, propagating the crack through the final 300-500 um posterior plate and separating the nuclear quadrants without mechanical counter-traction.
Viscodivision Technique in FLACS
💡3. Step-by-Step Surgical Protocol (4-Step Workflow)
Step 1: Cleavage Engagement ➔ Step 2: Dynamic Injection & Advancement
➔ Step 3: Posterior Plate Cleavage ➔ Step 4: Tactical Quadrant Removal
- Cleavage Engagement: Following hydrodissection, position the tip of a 27G Viscoat cannula directly at the center of the laser-cut cross or vertical fragmentation line.
- Dynamic Injection & Downward Advancement: Begin depressing the syringe plunger to initiate continuous OVD egress before and during cannula advancement into the cut. The continuous hydrodynamic flow opens the path and guides the cannula safely toward the base of the nucleus.
- Through-and-Through Crack: As the cannula approaches the posterior safety margin, the expanding viscoelastic mass breaks the final bridging fibers of the posterior plate. The nuclear quadrants spontaneously separate with zero mechanical stress.
- Tactical Quadrant Allocation:
- Limited OVD Volume (Focus on 1/4 Quadrant): Prioritize completely liberating a single quadrant. Once the first quadrant is emulsified and evacuated, central working space is established, allowing the remaining quadrants to be mobilized easily.
- Standard OVD Volume (Four-Quadrant Division): Sequentially apply Viscodivision into all fragmentation lines to divide all four quadrants completely before introducing the phaco handpiece.
💡4. Clinical Comparison: Viscodivision vs. Conventional Techniques
| Clinical Parameter | Viscodivision Technique (Dr. Alexander Chen) | Conventional Chopping / Phaco Re-Sculpting |
| Phaco Energy (CDE) | Zero additional sculpting energy; maximizes endothelial protection. | Consumes extra ultrasound energy to deepen laser-cut grooves. |
| Posterior Capsule Safety | OVD tracks downward to form a protective viscoelastic shield. | Sharp chopper or phaco tip operates in close proximity to naked capsule. |
| Zonular Shear Stress | Uniform hydrostatic pressure; near-zero lateral traction. | Bimanual mechanical cracking pushes against zonular apparatus. |
| Workflow & Efficiency | Executed in seconds with a single 27G handpiece. | Requires repetitive instrument exchanges and position adjustments. |
| Acoustic/Thermal Barrier | Base layer of OVD absorbs scattered thermal energy and cavitation waves. | Posterior capsule is directly exposed to phacoemulsification fluidics. |
💡About Viscodivision Technique FAQs
Q1: What is the Viscodivision Technique in cataract surgery?
Dr. Chen：The Viscodivision Technique is a surgical method developed by Dr. Alexander Chen for Femtosecond Laser-Assisted Cataract Surgery (FLACS). It uses continuous injection of dispersive OVD via a 27G cannula to hydraulically crack the uncut 300-500 um posterior nuclear plate left by the laser, achieving complete nuclear quadrant separation without ultrasound groove-sculpting.
Q2: Why does a femtosecond laser pre-cut nucleus still require division?
Dr. Chen： To avoid accidental laser rupture of the posterior capsule, FLACS software maintains an uncut 300-500 um posterior safety margin (posterior plate). Because this base layer remains intact, the quadrants remain attached at the bottom. Viscodivision uses hydraulic fluidics to crack this remaining tissue layer safely.
Q3: What is the recommended strategy if OVD volume is limited during Viscodivision?
Dr. Chen： When OVD volume is limited, the surgeon should focus entirely on achieving a through-and-through crack for a single 1/4 quadrant. Removing the first quadrant creates central working space in the capsular bag, allowing the remaining three quadrants to be removed without dividing them all beforehand.
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