A multifunctional crosslinking agent includes one or more repeating units of a siloxanyl group or a silyl-alkyl-siloxanyl group, and at least two ethylenically unsaturated reactive end groups. One of the at least two ethylenically unsaturated reactive end groups is a (meth)acrylate-containing reactive end group or an acrylamide-containing reactive end group and the other one is an allyl-containing reactive end group or a vinyl-containing reactive end group. Ophthalmic devices are formed from a polymerization product of a monomeric mixture containing one or more of the multifunctional crosslinking agents, one or more first ophthalmic device-forming comonomers having at least one reactive group that preferentially reacts with the (meth)acrylate-containing reactive end group or the acrylamide-containing reactive end group of the multifunctional crosslinking agent, and one or more second ophthalmic device-forming comonomers having at least one reactive group that preferentially reacts with the allyl-containing reactive end group or the vinyl-containing reactive end group of the multifunctional crosslinking agent.