The study enrolled children 6 to <48 months of age who had persistent NLDO after a failed probing. Other major eligibility criteria included onset of NLDO symptoms prior to 6 months chronological age; presence of at least one sign of NLDO (epiphora, increased tear lake, and/or mucopurulent discharge in the absence of an upper respiratory infection or ocular surface irritation); previous failed single primary probing procedure for NLDO; no history of nasolacrimal intubation, balloon catheter dilation, more than one probing, or dacryocystorhinostomy; and absence of Down syndrome.

The repeat probing surgery consisted of the dilation of at least one lacrimal punctum and the passage of a nasolacrimal probe into the nasopharynx at least once. Probe size was at investigator discretion. Procedures were performed under general anesthesia in a facility (ie, a hospital outpatient surgical department or ambulatory surgical center), or in the office without anesthesia at the preference of the investigator. Patency was confirmed in all cases by touching the probe in the nasopharynx with a second probe, by visualization of the probe beneath the inferior turbinate, or by recovery of fluorescein-colored saline from the nasopharynx after irrigation through the nasolacrimal system.

Subjects had follow-up visits timed 1 month (±1 week) and 6 months (±1 month) after surgery. At both visits, a trained and certified examiner other than the operating surgeon evaluated the presence or absence of each of three clinical signs of NLDO (epiphora, increased tear lake, and mucous discharge). In addition, a dye disappearance test (DDT) without topical anesthesia was performed by a certified examiner according to a protocol previously described.¹

Our finding of success in just over half of eyes with repeat probing is similar to several retrospective case series. Stager reported success with a second probing in 102 of 186 eyes (55%).² Katowitz and colleagues reported success with repeat probing in 52% (13 of 25) of children aged 6-18 months and in 18% (3 of 17) in children aged 18-24 months.³

Our study utilized prospective data collection with investigator certification and outcome assessment at a uniform time interval. However, the study has several limitations. Our results may be subject to selection bias because choice of procedure (repeat probing, NLD intubation, or balloon catheter dilation) was at the discretion of the surgeon. In addition, because of the small sample size, the confidence interval on our estimate of success rate was wide; therefore the estimate should be interpreted with caution. The sample size also precludes evaluating whether factors such as site of surgery or complexity of the obstruction have an impact on outcome. Finally, our outcome definitions of treatment success differ from those used by other authors, making direct comparison with results of other authors difficult.

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