New classification of ophthalmic viscosurgical devices—2005

Purpose

To revise the generally accepted classification of ophthalmic viscosurgical devices (OVDs) to include cohesion data and the new class of viscous dispersive OVDs.

Setting

York Finch Eye Associates, Toronto, Ontario, Canada, and Alcon Research Limited, Fort Worth, Texas, USA.

Methods

Pseudoplasticity and cohesion-dispersion (CDI) data of DisCoVisc (hyaluronic acid 1.6%–chondroitin sulfate 4%), a new viscous dispersive OVD, were determined and compared with existing OVDs. The existing classification of OVDs was unable to accommodate its properties, so the classification was modified to include a new class and other potential new classes which currently remain unoccupied.

Results

Current OVD classification, although based on the clinically significant rheologic parameters of zero-shear viscosity and cohesion, only uses zero-shear viscosity because of the high correlation of these 2 parameters in existing OVDs. The appearance of DisCoVisc forces modification of the existing scheme because it does not fit into a preexisting category. The new proposed broadened classification is changed from a 1-dimensional list into a 2-dimensional table and considers CDI independently from viscosity for all OVDs. Expansion of the classification of OVDs in this manner predicts further possible new innovative OVDs for surgical use.

Conclusion

The surgical behavior of OVDs can be predicted by their position in a classification of OVDs based upon zero-shear viscosity and cohesion.