Does precipitation reduce tissue staining by indocyanine green dye solutions?

PURPOSE: Indocyanine green (ICG) dye precipitates when mixed with certain ophthalmic irrigation solutions. The purpose of this study is to investigate whether this precipitation reduces ICG staining of the anterior lens capsule. METHODS: ICG was diluted with each of the following solutions: BSS Plus, physiological saline, or Opeguard Neo. The products were then examined for green precipitate by light microscopy. The tissue staining capability of each ICG solution was tested at two different concentrations (0.5% and 0.0625%) in porcine lenses, regardless of whether the solution contained precipitate. RESULTS: Green precipitate was observed in both concentrations of ICG solutions diluted with BSS Plus, but not in the solutions diluted with either physiological saline or Opeguard Neo. As assessed with light microscopy, staining of the anterior lens capsule appeared weaker for all 0.0625% ICG solutions compared to the corresponding 0.5% ICG solutions. The precipitate that formed in the 0.5% ICG solution diluted with BSS Plus had little effect on the staining quality of the anterior lens capsule. In contrast, the 0.0625% ICG solution diluted with BSS Plus (w/precipitate) showed weaker staining in the lens capsule compared to the other two 0.0625% ICG solutions (w/o precipitate). CONCLUSION: These results suggest that precipitation of ICG may weaken its capability to stain the anterior lens capsule or other transparent ocular tissues. Therefore, ICG solutions that do not form a precipitate may be more capable of staining tissues at lower concentrations. As for other possibilities to explain the deterioration in staining, the effect of the composition of BSS Plus should also be considered.