A punctum plug for blocking lacrimal fluid flow through a punctum and an associated canaliculus composed of a hydrogel material and a hydrophobic coating which covers the exterior surface of the hydrogel material. The hydrophobic coating averts adsorption of proteinaceous materials onto the hydrogel....http://www.google.es/patents/US5283063?utm_source=gb-gplus-sharePatente US5283063 - Punctum plug method and apparatus
