We know that a dispersive viscoelastic will protect the corneal endothelium better during phacoemulsification of the lens nucleus. And a cohesive viscoelastic is better for opening up the capsular bag to prepare for IOL insertion and is also easier to evacuate from the eye at the end of the surgery. But which type of viscoelastic is best for the IOL injector?
If we use a dispersive viscoelastic in the IOL injector, it will be more lubricating and it will coat the walls of the injector tip better. This makes it easier to squeeze a thicker lens (such as higher dioptric powers of +27 and above) through the smaller injector tips. This dispersive agent is thinner and more liquid in behavior. The challenge is that it is more difficult to aspirate from the eye. And if you leave dispersive viscoelastic adherent to the posterior surface of the optic, then the IOL can slip, slide, and rotate in the capsular bag. This is a problem that is important to avoid in toric IOLs especially. We can remedy this by placing the I/A probe behind the IOL optic to remove all of the dispersive viscoelastic. This is my typical technique.
If we use a cohesive viscoelastic in the IOL injector, it will not be quite as lubricating since it is more of a solid form (like jelly) instead of liquid (like honey). This may pose an issue when injecting a thicker lens, which could get stuck in the injector or damaged during delivery. This cohesive viscoelastic is much easier to remove from the eye and it does not adhere to the IOL optic. This can help with IOL rotational stability for surgeons who do not routinely go behind the IOL optic to remove viscoelastic.
Click below to watch this video and learn from the options: