Comparative purity of trypan blue solutions: Impurity profiles and their clinical implications

Following recent publications on microfiltered trypan blue 0.4% ophthalmic solution, some theoretical concerns have been raised about the potential toxicity of this higher than standard concentration. Research into this matter has revealed that concentration is not the concern, instead the fundamental issue is the level of impurities present and their clinical implications—specifically monoazo compounds. This article reviews the evidence and highlights the concentration of dye, dose of dye used, concentration of impurities in a number of available trypan blue products. High-performance liquid chromatography demonstrates that CAPSULBlue, VisionBlue and MembraneBlue have much higher purity levels having been made from trypan blue for use in humans. Monoazo levels are also much lower and practically non-existent in CAPSULBlue. No incidence of toxic anterior segment syndrome has been reported in these high purity products.