Purpose: to compare the results of probing alone versus primary silicone intubation in cases of complex congenital NLDO.

Patients and methods : The study was done in ophthalmology department, Zagazig university hospitals from May 2022 to December 2023. Patients with complex CNLDO in children aged 1 - 4 years were included. We excluded cases of simple CNLDO , failed previous probing or intubation. Patients were divided randomly into two groups. The first group (group I) (32) eyes were treated with intubation and the second group (group II) (32) eyes were treated with probing and syringing.

Results : 64 patients with complex type of CNLDO were enrolled. There was no significant difference between both groups regarding age (P = 0.990) and gender (P = 0.448). Failure rates were significantly higher in group II than in group I at one week (40.6 percent vs. 15.6 percent, P = 0.026) . The results remained constant at the first and third month postoperative in which the failure rates at group II vs group I were (56.3 % vs. 15.6 %, P 0.001), and the results were also the same at the fourth and sixth month with the failure rates at group II vs group I were (68.8 % vs 15.6 % , P 0.001).

Conclusion: Primary silicone intubation is recommended in cases of complex CNLDO because it produces better results than probing and has a longer success rate.

Keywords:1- Probing 2- Silicon intubation 3- Complex CNLDO 4- Simple CNLDO.