Fluorescence characteristics of sodium fluorescein–rose bengal ophthalmic solution mixtures

PurposeTo assess fluorescence emission properties of sodium fluorescein–rose bengal mixtures in buffered aqueous solution.MethodsSolutions 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.ResultsThe 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.ConclusionsThe 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.