Device for packaging and dispensing drops of a substance for ophthalmic use, generally fluid, semi-fluid or in suspension, emulsion or oily solution including a dispensing accessory with a first valve made of an elastomer material that allows the substance to pass through when the dispensing accessory is stressed, without allowing outside air to pass through in the opposite direction when the dispensing accessory is relaxed, characterized in that the first valve is covered by a layer of Parylene.