Ear drops and grommets.

The relative ease with which different ear drops pass through grommets of different designs has been investigated using a laboratory model. The viscosities of the various ear drop preparations tested have also been determined. There is a considerable variation in the volume of ear drops required to penetrate ventilation tubes. Their ease of passage is determined by the size of the tube and is probably also related to the ease with which a preparation wets the surface of the grommet. There is no relationship between ease of penetration and viscosity. The penetration of ear drops through grommets during episodes of aural discharge was studied in vivo. Penetration into the middle ear was observed only when the drops were introduced using the displacement technique. It was more readily achieved when the grommet lumen was free of discharge.