The role of "after washing imaging" in evaluation of tear drainage system by dacryoscintigraphy

BACKGROUND: The aim of this study was to evaluate the efficacy of "after washing" imaging in interpretation of dacryoscintigraphy as a functional imaging technique used in evaluation of tearing problems. MATERIALS AND METHODS: 300 nasolacrimal systems were studied. 100 mu Ci of technetium-99m sodium pertechnetate as drops of activity (10 mu L) were placed into the inferior fornix of each eye. Dynamic images were obtained for 15 minutes in the sitting position. "After washing" phase was done by placing a drop (10 mu L) of normal saline in each eye and external ocular massage for an additional 10 minutes. The imaging patterns for each eye in the first dynamic phase and after washing phase were recorded, separately. RESULTS: First dynamic phase demonstrated a sensitivity of 97.4% and specificity of 22.6%. After washing phase showed a sensitivity of 91.2% and specificity 75.5%. After washing test, the obstruction pattern changed to "patent nasolacrimal duct" or "further progression" of the radiotracer to the nasolacrimal duct in the 25.1% and 24.4% of the nasolacrimal systems, respectively. CONCLUSIONS: After washing imaging is a useful method in dacryoscintigraphy which can improve the specificity of scan for diagnosis of lacrimal duct obstruction. It can also improve the localization of obstruction level in the lacrimal systems.