Characterization of Contact Lens Plastics

Abstract

In the development of contact lens material, characterization of the materials includes measurement of gas transport, and mechanical properties, including the modulus of elasticity, tensile strength, percent elongation and tear strength. Physical properties determined on contact lens plastics include percent hydration, wetting angles, glass transition temperature, percent visible transmission, indentation hardness, refractive index, and percent linear expansion. In addition to polymer measurements, the protein and lipid deposition must be measured to determine biocompatibility in the eye. Each of the measurements must be performed on a finished contact lens which weighs 10 mg at a thickness 0.01 cm. This paper will describe how each of the listed measurements is performed on a contact lens and representative measurements will be given for contact lens polymers. This data will include both rigid gas permeable and hydrogel contact lenses.