Higher-viscosity dispersive viscoelastic holds promis

San Diego-A new ophthalmic viscoelastic device (OVD) has been developed, which should be available in late 2004, that is the first to provide high viscosity as well as dispersive properties.

"The implications of this product are new to ophthalmic surgeons. It presents exciting new opportunities and may be useful to train new surgeons," Steve Arshinoff, MD, explained at the American Society of Cataract and Refractive Surgery annual meeting.

"When using a new OVD, it is crucial that we understand how it works. Their properties determine how they are classified, and the classification helps us understand how different types of OVDs perform in surgery," Dr. Arshinoff explained.

"Viscoelastics were listed according to zero shear viscosity but both cohesion and dispersion were discussed," he stated.

"DisCoVisc [Alcon Laboratories], however, is a bit different from previous viscoelastics," he said and demonstrated the plot of the agent's viscosity versus the log of the shear rate.

At zero shear viscosity, he noted, the new OVD is very similar to Healon (Advanced Medical Optics), but a bit more viscous when injected through a cannula. Compared with Viscoat (Alcon Laboratories), there is considerably more viscosity at low shear rate.

On a plot of cohesion of various viscoelastics, he showed how much of the new OVD is aspirated out of a beaker over 2 seconds when it is pulsed with high vacuum. Compared with Healon GV and ProVisc (Alcon Laboratories), most of the DisCoVisc comes out in quantities proportional to vacuum applied, more similar to Viscoat, thanks to cohesive OVDs. DisCoVisc is therefore dispersive like Viscoat, but not quite as dispersive. DisCoVisc will therefore be the only viscous-dispersive OVD available, Dr. Arshinoff demonstrated.

When considering the value of this new surgical device, Dr. Arshinoff pointed out that if consideration is given to why a viscous dispersive device is desirable, it is apparent that the material provides excellent anterior chamber maintenance, such as that achieved with Healon, as well as longer retention time during phacoemulsification in long and difficult cases, similar to that with Viscoat. In addition, the new OVD can be removed more easily during I/A, as with Healon and other cohesive agents, when compared with dispersive agents, such as Viscoat.

"It is anticipated that this new OVD will provide unique properties in one syringe. Also it may be particularly advantageous for teaching residents or surgeons learning to perform phacoemulsification," he said.