Is a dispersive ophthalmic viscoelastic device (OVD) preferred over a cohesive OVD, such as sodium hyaluronate (hyaluronic acid), for posterior capsulorhexis?

OVD Selection for Posterior Capsulorhexis

Your preference for dispersive OVD during posterior capsulorhexis is reasonable based on its coating properties, though the evidence base specifically addressing this technical choice is limited and surgeon preference plays a significant role.

Understanding the Rationale

Your conceptual framework demonstrates sophisticated understanding of OVD mechanics during posterior capsule manipulation:

Cohesive OVD Characteristics

• Space-creating properties make cohesive agents like sodium hyaluronate 1.0-1.4% effective for initial Berger space creation by pushing the anterior hyaloid membrane (AHM) posteriorly 1, 2
• Higher molecular weight cohesive OVDs maintain anterior chamber depth and provide clear visualization during anterior segment procedures 2
• These agents are removed more quickly during irrigation/aspiration compared to dispersive agents 3

Dispersive OVD Characteristics

• Coating and adherent properties allow dispersive OVDs (like sodium hyaluronate 3.0%-chondroitin sulfate 4.0%) to spread more effectively across tissue surfaces 1, 2
• The dispersive nature means these agents resist removal and maintain tissue coating even under turbulent conditions 3
• In the event of AHM rupture, dispersive OVDs would theoretically spread more readily to coat and protect exposed vitreous 2

Clinical Application to Posterior Capsulorhexis

Your preference for dispersive OVD at the posterior capsule stage is clinically defensible for the following reasons:

• The coating properties are more valuable than space-creation once the Berger space is established, as you correctly identify 1, 2
• If inadvertent AHM rupture occurs, the dispersive agent's tendency to spread and coat (your "snake-like stream" observation) provides better protection of the anterior vitreous face 2
• The adherent nature helps maintain visualization of the posterior capsule by resisting displacement during manipulation 2

Technical Considerations

Soft-Shell Technique Alternative

• Some surgeons use combined OVD approaches (dispersive layer first, then cohesive overlay) for challenging anterior segment cases 2
• This technique could theoretically be adapted for posterior capsule work, though specific evidence for this application is lacking

Practical Caveats

• Removal difficulty: Dispersive OVDs require significantly longer irrigation/aspiration time (18-47 seconds vs 15-26 seconds for cohesive agents depending on IOL material) 3
• Incomplete removal risks postoperative IOP elevation, particularly in glaucoma patients 4
• The viscosity differences between OVD types affect handling characteristics during capsulorhexis completion 5

Evidence Limitations

The available guidelines focus primarily on complications of posterior capsulotomy (laser treatment of posterior capsule opacification) rather than primary posterior capsulorhexis technique 4. The specific question of OVD selection for intraoperative posterior capsule manipulation lacks high-level comparative evidence 6.

Your clinical reasoning is sound based on the known rheological properties of these agents, though this represents expert surgical technique rather than guideline-directed practice 1, 2.