AIM: To investigate the clinical features of congenital nasolacrimal duct obstruction and affecting factors of the outcome of lacrimal probing.METHODS:We retrospectively analyzed 616 infants (687 eyes) with congenital nasolacrimal duct obstruction who underwent lacrimal probing in the Department of Ophthalmology of Shenzhen Children's Hospital between June 2010 and May 2011. The main study items include the following: age at the initial consulting, age at the time of lacrimal probing, gender, mode of delivery, purulent secretion, past history of lacrimal rinsing, past history of lacrimal probing. We sumed up the clinical features and investigated the possible relationship between the above clinical parameters and success rate of lacrimal probing. The criterion for success of lacrimal probing is defined as: disappearance of epiphora and purulent secretion, and patency confirmed by lacrimal rinsing.RESULTS:There was no significant difference on the success rate of lacrimal probing between natural birth and Cesarean birth (P=0.376). The success rate of lacrimal probing between male and female infants also showed no significant difference (P=0.498). The success rate of lacrimal probing is negatively associated with the age at the time of lacrimal probing (P=0.001). The success rate of lacrimal probing at 3, 6, 9, 12 and 15 months was 100%,97.8%,90.8%,83.3% and 76.5% respectively (P=0.018). The success rate of lacrimal probing in infants with purulent secretion was significantly decreased (P=0.013). Past history of lacrimal rinsing did not influence the success rate of lacrimal probing (P=0.561). However, infants with past history of lacrimal probing showed significantly reduced success rate of lacrimal probing as compared with those without past history of lacrimal probing (P=0.042).CONCLUSION:The success rate of lacrimal probing for congenital nasolacrimal duct obstruction decreased significantly with the increasing age. Purulent secretion was also risk factor for the failure of lacrimal probing. It is important to effectively control local inflammation and perform lacrimal probing as earlier in order to increase the success rate of lacrimal probing for infants with congenital nasolacrimal duct obstruction.