The dynamic film thickness of cushioning agents on contact lens materials.

Using an in vitro technique, a number of commercial as well as pure polymer solutions were evaluated for their ability to form thick aqueous layers on contact lens materials. It was demonstrated that the thickness of adhered pure polymer films was strictly viscosity dependent and did not depend upon the solution's wetting properties (ie, contact angle and surface tension) nor the surface upon which the solution was deposited (eg, glass, a hydrophilic surface versus Plexiglass, a relatively hydrophobic surface). The clinical implications of this study are that the desired solution properties of tear substitutes may be quite different from those of wetting and "cushioning" solutions.