Siloxy-containing monomers, macromonomers, or polymers have at least a siloxy-containing side group that comprises a refractive-index increasing substituent. Polymeric compositions comprising such siloxy-containing monomers, macromonomers, or polymers are advantageously used for making ophthalmic devices, such as intraocular lenses, contact lenses, corneal rings, corneal inlays, and keratoprostheses.