Objective: Assessment of the prognostic value of the FDD test (fluorescein dye disappearance test) for treatment of congenital occlusionof the lacrimal pathways by means of silicone intubation and for assessment of the time of removal of the cannula. Method: The drainage function of the lacrimal pathways was evaluated perspectively in a group of 46 children with inborn occlusin of the lacrimal pathways, aged 1-3 years, treated by means of silicone intubation. The evaluation was made before insertion of the cannula, one week, one month after the operation, during removal of the cannula, one month and one year after its removal. The results of FDDT were compared with the clinical condition and the therapeutic results. Results: In all instances (36 children) where shortly after surgery regression of the signs and symptoms of occlusion occurred and FDDT was 0-1 the long-term result (one year after removal of the cannula) of treatment was favourable. Nine of 11 cases where FDDT 2-3 and signs of occlusion persisted also when the cannula was removed after its removal marked improvement of the symptoms of occlusion occurred or they disappeared and the drainage of the lacrimal pathways was normal. If FDDT suggests during the period with the inserted cannula a satisfactory function of the lacrimal pathways, the prognosis of cure is good and the cannula can be removed already after 6-8 weeks. If during the time with the cannula the impaired drainage function of the lacrimal pathways persists, i.e. FDDT 2-3, it is better to remove the cannula not sooner than after 5-6 months. Conclusion: FDDT can serve as a prognostic factor in the treatment of congenital occlusiom of the lacrimal pathways by means of a silicone cannula and for assessment of the time of its removal.

        Key words: congenitalocclusion - intubation -FDDT- intubationperiod -prognosis