How does the thickness of the zona pellucida influence injection strategy ?

• Thick or Hardened Zona: Increase bevel length slightly (5–10 µm) and raise injection pressure by 1–2 hPa.

• Pre-treatment: Brief acid-Tyrode or calcium-free incubation can soften the zona, reducing required force.

• Monitoring: Watch for “give” as the tip traverses the zona—avoid over-penetration beyond that point.