We use viscoelastic (also called OVD = ophthalmic visco-surgical device) during cataract surgery to protect the delicate intra-ocular structures, in particular the corneal endothelium. For a dense cataract where we use more ultrasonic energy and fluidic currents, we can re-inject additional viscoelastic that may have been washed out. We can also use the OVD to create a barrier between the phaco tip and the posterior capsule. In this video our guest surgeon uses a continual injection of OVD to protect the cornea and posterior capsule during phaco of a dense cataract.
Decent idea but I think the challenge for most people would be keeping perfect control of the canula for an extended period of time while pushing on the plunger.