The Soft-Shell Technique for viscoelastic use in cataract surgery was developed by Dr. Steve Arshinoff as a method of getting the best of both types of viscoelastics. Since dispersive OVDs protect the corneal endothelium the best and cohesive OVDs provide the most working space and best flattening of the anterior lens capsule for capsulorhexis creation, the idea is to use both in the anterior chamber together.
First a dispersive OVD is injected into the anterior chamber and aimed towards the undersurface of the cornea. Next the cohesive OVD is injected underneath this and that pushes the dispersive OVD up against the corneal endothelial surface while the cohesive OVD flattens the anterior lens capsule to facilitate capsulorhexis creation. Thus, we get the benefits of both the dispersive and the cohesive viscoelastic in the same case.
There are other variations on this technique such as using three layers: dispersive OVD for the cornea, then cohesive OVD to make space, then balanced salt solution under the cohesive OVD to create a small space to allow trypan blue staining of the anterior lens capsule. We can also use visco-adaptive agents as well as dispersive and cohesive ones. The variations are seemingly endless.
In routine cases, I do not find a benefit of using the soft-shell technique, but other surgeons rely on it for every case. Try the technique yourself and then decide if it is suited to your technique of surgery and your patient population.
Click below for a video of the Soft-Shell Viscoelastic Technique in Cataract Surgery: