Deposition of aerosol particles in a model vitreous chamber

The purpose of this study was to assess quantitatively the aerosol deposition in a model eye chamber to identify the mechanism(s) of deposition and delivery efficiency for application in retinal disease treated with vitrectomy. Dry aerosol particles were produced with mixtures of fluorescein and a variable concentration of cesium chloride, which ranged in aerodynamic size from 0.6 to 1.3 µm. The aerosol was injected through a small inlet tube into Teflon chambers that had a vented, spherical cavity (diameter ¾"). Two filling times of 60 s and 90 s were used. Although significant loss occurred in the syringe, the mass deposited within the chambers increased with aerosol concentration and ranged from 0.5 to nearly 15 µg. Between 60 and 90% of the mass was deposited on the lower surface of the chamber. The mechanism of deposition was consistent with diffusion through a boundary layer during filling followed by sedimentation of the remaining suspended aerosol particles. Based on these results, an aerosol with a median particle size of 1.3 µm was shown to provide a therapeutically effective dose of 5-fluorouracil. The approach is general and can be applied to the aerosol delivery of other drugs to the vitreous chamber.