US Patent 7828432 Hybrid contact lenses prepared with expansion controlled polymeric materials

A hybrid contact lens includes a substantially rigid center portion and a substantially flexible skirt portion connected to the center portion. The skirt portion is formed using xerogels compatible with diluents comprising at least one selected from polylactic acid, polyglycolic acid, lactide, glycolide, a polyacetal, a cyclic acetal, a polyketal, a cyclic ketal, a polyorthoester, a cyclic orthoester, di-t-butyl-dicarbonate, tris(trimethylsilyl)amine, and 2,2,2-trifluoroacetamide. These diluents are formulated to function as a stand-in for water in the xerogel polymer, allowing the xerogel to form and bond to the rigid center portion in its fully expanded state. Upon hydration of the hybrid lens, substantially little dimensional change, and thus substantially little distortion, is obtained in the skirt portion. The diluents of the present invention further preserve the mechanical integrity of the xerogel, allowing the xerogel to be machined to final shape, improving the dimensional tolerances which can be achieved in the hybrid lens.