Purpose: To quantify the surface retention of several ophthalmic viscoelastic agents following irrigation and aspiration (I/A) using a new in vitro method.
Setting: Alcon Laboratories, Inc., Fort Worth, Texas, USA.
Methods: A rabbit corneal endothelial cell line was cultured to confluency in 24-well plates, and the cells were labeled quantitatively with internalized neutral red dye. Five ophthalmic viscoelastic agents were applied to cover the monolayer of cells: sodium hyaluronate (Healon, Provisc, and Amvisc Plus), Formulation A (a dispersive, nonproteinaceous, synthetic polymer), and sodium chondroitin sulfate, sodium hyaluronate (Viscoat). Irrigation and aspiration (with fluid turbulence similar to that encountered in phacoemulsification surgery) were performed on each well for 3 minutes, using 120 mL of balanced salt solution with bicarbonate. dextrose, and glutathione (BSS Plus). The cells were treated with an acidified ethanol solution to extract the dye from the cells left without a viscoelastic cover. The extracted dye was measured by spectrophotometry and compared with the total dye recovered from control cells.
Results: The retention value, which represented the percentage of cells with viscoelastic retained on the surface, was calculated as follows: Healon, 7; Provisc, 16; Amvisc Plus, 17; Formulation A, 55; Viscoat, 90. On a nonadsorptive, non-cell surface, the retention values of the five viscoelastics were significantly less than those on cells.
Conclusion: The results of this experimental model suggest that cohesive viscoelastics are readily removed from the cells, while dispersive viscoelastics are highly retained. In addition, mutual surface interaction (electrical charge and other properties) plays a significant role in determining the retention of viscoelastics on the corneal endothelial cell surface following I/A.