A cylindrical plug for insertion through the punctum and into the canaliculus to block the flow of tears therethrough comprises an insert of a material which when hydrated expands and changes shape, conforming at least to a portion of the canaliculus crossection and contacting the walls of the canaliculus, thus blocking flow. The plug can be inserted in a dry state and hydrating in situ or hydrated, either partially or fully, prior to insertion.
