Joseph A. Mcgee

In-Situ Surface Modification of Contact Lens Polymers

Soft contact lenses provide vision correction (myopia, hyperopia, presbyopia and astigmatism), cosmetic alterations such as color, or can be used as a therapeutic device. It has been proposed that the biocompatibility of the lens is determined in part by the wettability of the surface in the ocular environment.1 A nonwetting lens surface will cause discomfort and the potential for increased deposits. The deposits or biofiim on a contact lens affect vision, lens properties and ocular health.2,3 Thus, morphology and the surface chemistry of a contact lens can determine the resultant behavior witnessed by a practitioner in a clinical setting. Contact lens surfaces must remain clear and wetted, provide an adequate supply of atmospheric oxygen to and adequate expulsion of carbon dioxide from the cornea, maintain normal tear fluid flow and not abrade the ocular surface or eyelids.4 As research advances toward new materials that provide significant improvements in eye physiology, more attention is being focused on contact lens surface properties. Soft contact lens materials have bulk physical properties that dictate the type of polymer to be used. These properties include water content, refractive index, elasticity, light transmittance and tear strength. Often, polymeric materials with desired bulk properties are deficient in surface properties of wettability, lubricity and tear component deposition. Since the biocompatibility of a contact lens polymer is highly dependent upon the interactions of the polymer surface with ocular tissue and tear fluid, it may be necessary to modify the surface chemistry to achieve both the desired bulk and surface properties.