Fluorescence characteristics of sodium fluorescein–rose bengal ophthalmic solution mixtures

Purpose: To assess fluorescence emission properties of sodium fluorescein-rose bengal mixtures in buffered aqueous solution. Methods: Solutions of sodium fluorescein (NaFl) or rose bengal (RB) or mixtures of these two chemicals were prepared over a range of dilutions in 1% NaCl with 10. mM phosphate buffer to give a pH of 7.5 at room temperature. Absorbance and fluorescence spectra were recorded in 10. mm path length cuvettes. Results: The fluorescence emission from NaFl extends between 480 and nearly 600. nm, a spectral range that is also covered by the absorbance of RB (between 500 and 580. nm). With very dilute solutions of NaFl (less than 0.002%), an apparent total quenching of its fluorescence can occur in the presence of 0.01% RB, with a proportionate decrease at lower concentrations of RB. Conclusions: The presence of RB in an aqueous solution of NaFl at physiological pH appears to act in a similar way to a barrier filter, resulting in the quenching of the measurable fluorescence from NaFl. It remains to be established how substantial or significant such an effect might be if a mixture of NaFl and RB as used as part of the examination of the external eye.