Rose bengal dye concentration and volume delivered via dye-impregnated paper strips

Purpose. The technique of administration and the resulting volume and concentration of the dye delivered to the eye via dye-impregnated paper strips are not standardized or known. The purpose of this study was to use a standard technique for preparation of rose bengal dye from commercially available paper strips to determine the variability in concentration based upon soak time, and to determine the volume delivered by such a technique to a model eye. Methods. Rose bengal filter paper strips were wetted for either 15, 30, or 45 s, and the resulting concentration of dye eluted was determined by spectrophotometry. With the same preparation technique and a 15-s soak time, the strip was applied to wetted filter paper, as a model for the moist surface of the eye. The volume of solution delivered was calculated by weight. Results. Concentrations of rose bengal for the various soak times were: 15 s: 7.64 (+/-1.11) by 10(-6) g/ml; 30 s: 9.70 (+/-1.79) by 10(-6) g/ml; and 45 s: 10.27 (+/-0.66) by 10(-6) g/ml, The volume delivered to the eye model with this technique was 17.43 mu l (+/-3.09). Conclusions. The concentration of rose bengal dye delivered to the ocular surface by means of a wetted strip is relatively low and soak time/technique-dependent. This suggests a possibility that results in clinical studies with rose bengal strip application may be different than if controlled volume applications of commercially available 1% liquid rose bengal dye are used.