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A prospective, randomised comparison of probing versus bicanalicular silastic intubation for congenital nasolacrimal duct obstruction
  1. Yasser H Al-Faky,
  2. Ahmed Mousa,
  3. Hatem Kalantan,
  4. Abdullah Al-Otaibi,
  5. Hessah Alodan,
  6. Adel H Alsuhaibani
  1. Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
  1. Correspondence to Dr Yasser H Al-Faky, Ophthalmology Department, College of Medicine, King Saud University, PO Box 245, Riyadh 11411, Saudi Arabia; alfaky{at}


Purpose To compare the success rates of probing versus bicanalicular silastic intubation as the primary treatment for congenital nasolacrimal duct obstruction (CNLDO) in children ≥1 year old.

Study design Prospective, randomised, comparison.

Methods Participants were randomised to undergo probing or bicanalicular silastic intubation. In bilateral cases, the right eye was used for analysis. The procedure was considered successful when all preoperative manifestations disappeared with normal dye disappearance test and a positive Jones primary dye test at least 6 months postoperatively. Secondary outcomes were risk factors for failure. Outcomes were compared between treatments with p<0.05 indicating statistical significance.

Results 207 eyes of 181 children between 1 and 8 years old with CNLDO who had not undergone previous surgical treatment were included in the study. 88 eyes underwent probing with a 84.1% success rate and 93 eyes that underwent bicanalicular silastic intubation had a 89.2% success rate (p=0.429). For simple CNLDO, there was a 94.2% (65/69) success rate with probing and a 90.9% (60/66) success rate with bicanalicular silastic intubation (p=0.687). In complex CNLDO, there was a 47.4% (9/19; p=<0.001) success rate with probing and an 85.2% (23/27; p=0.419) success rate with silastic intubation (p=0.016). Age was not a risk factor for failure in either procedure.

Conclusions Probing for simple CNLDO in young children is adequate. Bicanalicular silastic intubation seems to have a role in achieving successful outcomes in complex CNLDO.

  • Embryology and development
  • Lacrimal drainage

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Probing versus silastic intubation in the management of congenital nasolacrimal duct obstruction (CNLDO) is subject to debate with no consensus on the selection of the procedure as high success rates have been reported with both procedures.1–7 Some have encouraged silastic intubation as a primary procedure despite the fact that probing has lower complications and is relatively easy to perform.2 ,8–14 Reasons for encouraging silastic intubation include declining success rates of probing with age and successful silastic intubation after a failed probing. However, comparison of these procedures is tenuous at best as much of the published literature is based on retrospective studies, differing selection criteria, varying age of the study cohorts, and variable outcome measures.1 ,2 ,4 ,6 ,8 ,15 A fair number of previous studies are prospective, but none is comparative or randomised.5 ,7 ,10 ,12 ,16 ,17

To our knowledge, no prospective, randomised comparison of probing versus bicanalicular silastic intubation for CNLDO has been published in the English peer reviewed literature. In this study we compare the success rates of probing versus bicanalicular silastic intubation as the primary treatment for CNLDO in children ≥1 year old.

Patients and methods

The study was approved by the institutional review board and adhered to the tenets of the Declaration of Helsinki. All subjects were diagnosed and treated between August 2009 and April 2013. Informed consent was obtained from the parents or guardians of the children.

Eligibility criteria

Inclusion criteria were children aged 1 year or older with epiphora and/or discharge before 6 months of age in the absence of upper respiratory tract infection or ocular surface irritation. Enrolment for surgical intervention for the first time to treat CNLDO was mandatory. Exclusion criteria included punctal disease, previous history of acute dacryocystitis, eyelid malposition, Down syndrome, craniofacial anomaly, history of previous surgical intervention for CNLDO, and bony nasolacrimal duct (NLD) obstruction.

Patient enrolment

The presence/absence and severity of epiphora, increased tear lake and discharge were documented preoperatively. Epiphora and discharge were graded as mild if it occurred once per week, moderate if occurred 2–6 days per week, and severe if it occurred daily. The type of discharge was documented as mucoid or mucopurulent. An increased tear lake was graded as: grade 1 if it was observed on examination and noticed by parents but was not overflowing; and grade 2 if it continuously dripped over the cheek.

A dye disappearance test (DDT) without topical anaesthesia was performed in all patients and recorded as positive (if it disappeared or there was faint dye in the tear film after 5 min), negative (if there was a thick meniscus of fluorescein-tinted tears with a deeply stained conjunctival cul-de-sac with dye after 5 min), and delayed (if the dye partially disappeared after 5 min or there was a lightly stained conjunctival cul-de-sac after 10–15 min). The Jones primary dye test was performed for all patients and reported after 5 min as positive (normally patent lacrimal passage either through direct visualisation of the fluorescein dye in the inferior meatus under cobalt blue-filtered light after enhancement by asking the patient to blow his nose, if possible; or direct retrieval of the dye with a fine nasopharyngeal swab placed in the inferior meatus (figure 1)) or negative (failure to visualise or retrieve the dye from the inferior meatus).

Figure 1

A fine nasopharyngeal swab (right side) compared to other larger diameter swab or cotton tipped applicators.

Sample size calculation, randomisation, and study end point

Sample size was estimated considering an expected difference of 10% in success rate, and an accepted difference of 5%. Power was set to 90%, α error to 0.05 (z 1-α/2: 1.96), and β error to 0.1 (z 1-β: 1.282), which yielded a total sample size (accounting for bilateralism) of 84 subjects in each arm. A 5% contingency was added to overcome decrements which eventually were adjusted to 93 subjects per each arm.

Randomisation was carried out by a biostatistician who was not involved in the clinical work of this study. Patients were randomly assigned, in a 1:1 ratio, to receive or not receive bicanalicular silastic intubation. A set of computer generated random numbers were obtained before randomisation and kept in a safety lock. Surgeons had no access to the random numbers which were allocated in the operating room before the surgical intervention. In bilateral cases, the selection of the procedure was randomised in the first eye to undergo surgery and the fellow eye underwent the alternative procedure.

The study end point was 6 months after surgery. In the case of clear failure (moderate or severe mucopurulent discharge and/or positive regurgitation), the outcome end point was considered as early as 1 month postoperatively in the case of probing and 3 months (stent removal follow up visit) in the case of bicanalicular silastic intubation. The early study end point allowed the surgeon to proceed with further management in failed cases.

Surgical procedure and techniques

All surgeries were performed with the patients under general anaesthesia. Four surgeons performed the procedures in this study (YHA-F, AO, HA, AHS). For probing (probing group) the surgical steps included dilation of the upper punctum and irrigation of the lacrimal drainage system (LDS) to diagnose partial obstruction, followed by passage of lacrimal probe # 1 through the lacrimal passage to the inferior meatus. Patency was confirmed by metal-to-metal touch by passing another probe through the nostril (this aided the diagnosis of submucosal opening of the NLD), followed by irrigation with fluorescein dye. The nature of the obstruction was classified as simple (thin membrane at the lower level of the NLD which was bypassed easily using probe #1 without any gritty sensation) or complex (unusual site of obstruction at the upper or mid NLD, tight obstruction with a gritty sensation during passage of probe #1, thick membrane which required a smaller probe size and greater force to bypass, NLD obstruction associated with canalicular obstruction, or any difficulty due to anatomical variations such as a shallow inferior meatus).

The surgical procedure for bicanalicular silastic intubation (silastic intubation group) was similar to probing followed by the Ritleng system for intubation (S1-1451, FCI Ophthalmics, Issy-Les Moulineaux Cedex, France). The two ends of the silicone tube were tied and fixed to the lateral nasal wall mucosa using 5/0 polyglactin 910 suture to avoid early tube dislodgement. Any difficulty with intubation, damage to the nasal mucosa or inferior turbinate infracture was documented. Postoperatively, combination antibiotic–steroid drops were prescribed four times daily for 1 week then twice daily for another week.

Follow-up examination

The ophthalmologist who performed the postoperative examination did not participate in preoperative evaluations or perform any surgery in this study.

Postoperative visits were performed at 1 month, 3 months, and 6 months. At each follow-up visit, the preoperative clinical signs and symptoms were reassessed and the same tests were performed (epiphora, increased tear lake, discharge, DDT, and Jones primary dye test). In-office removal of the silastic tube was performed at 3 months postoperatively by the treating physician. The tube was removed by displacing the tube knot through the upper canaliculus, then cutting and removing the tube. Any silastic tube related complications were documented.

Major outcome measures and statistical analysis

Preoperative data were collected for gender, age at intervention, and clinical features. The procedure was considered successful when all preoperative manifestations disappeared with normal DDT and a positive Jones primary dye test. Secondary outcomes were risk factors for failure.

Data were collected in a specifically designed data collection sheet, reviewed and stored in a Microsoft Access (V.2007) database (Microsoft Corp, Redmond, Washington, USA). Statistical analysis was performed with SPSS V.19.0 (IBM Corp, Armonk, New York, USA), Medcalc 11.6 (MedCalc Software, Mariakerke, Belgium), and Statpac 11.0 (StatPac Inc, Bloomington, Minnesota, USA). Descriptive analyses and inferential analyses were performed with the χ2 test to evaluate the association between potential risk factors and failure (Fisher's exact test when indicated). The Student’s t test was used to compare groups in terms of continuous variables while comparison of proportion test was performed to compare success rates across groups. A value of p<0.05 was considered statistically significant.


A total of 202 patients, involving of 228 eyes, were enrolled. Eleven patients were excluded because of lack of complete follow-up, and exclusion criteria ruled out another 10 patients. The study group included 207 eyes of 181 patients (91 males (50.3%) and 90 females, 155 unilateral (85.6%) and 26 bilateral) with a mean (±SD) age at intervention of 29.1±15.6 months (range 12–90 months). In bilateral cases, only the right side of such cases was used for data analysis as it was thought likely that the outcome could be correlated to bilateralism. There were 88 probings and 93 bicanalicular silastic intubations performed for this study. Demographics of each group are summarised in table 1.

Table 1

Demographics of the probing and bicanalicular silastic intubation groups

The success rate was 84.1% (74/88) in the probing group and 89.2% (83/93) in the bicanalicular silastic intubation group (p=0.429). Patients were subdivided into two groups based on age: from 12 months to ≤36 months; and >36 months. The preoperative characteristics are presented in table 2.

Table 2

Preoperative characteristics of patients who underwent probing or bicanalicular silastic intubation for congenital nasolacrimal duct obstruction

The preoperative characteristics had no statistically significant effect on the treatment outcome of probing versus bicanalicular silastic intubation or within the same group for either procedure. Bilateral cases had 88.5% (23/26) successful probing and 96.2% (25/26) successful bicanalicular silastic intubation (p=0.298). Early dislodgement of the silastic tube occurred in nine eyes (six eyes within 2 weeks), yet none failed. One patient aged 14 months had slit canaliculi induced by the silastic tube with mild postoperative epiphora. This was considered a failed procedure (despite a patent Jones dye test), as it did not meet the success criteria.

Simple CNLDO was detected in 135 eyes while complex CNLDO was detected in 46 eyes. For simple CNLDO, there was a 94.2% (65/69) success rate with probing and a 90.9% (60/66) success rate with bicanalicular silastic intubation (p=0.687). In complex CNLDO, there was a 47.4% (9/19; p=<0.001) success rate with probing and 85.2% (23/27; p=0.419) success with silastic intubation (p=0.016). The causes and individual success rates of complex CNLDO are summarised in table 3.

Table 3

Characteristics of patients with complex congenital nasolacrimal duct obstruction (CNLDO) who underwent probing or bicanalicular silastic intubation


Probing and silastic intubation remain the favoured procedures to treat CNLDO.18 Probing is reported to have high success rates, is a relatively easy procedure to perform, and no stress is put on family members by having a foreign body in their child's eye.1–3 ,10 ,11 Silastic intubation also has high success rates and has been credited for older age groups and secondary intervention.9 ,11 ,12 ,14 The assumption is that the silicone tube acts as a scaffold for tissue healing to mould around it, preventing obstruction and maintaining a patent LDS.19 As CNLDO is seldom reported in animals, this assumption could not be proved in animal models.20 ,21 Hence, evaluation of the role of silastic intubation to maintain patent NLD is tenuous at best, and a prospective, randomised, comparative study is required to answer the age old question—is probing or silastic intubation better for CNLDO?

The results of our study show comparable success rates for both probing and bicanalicular silastic intubation in the study cohort and the sub-group with simple CNLDO. These outcomes indicate that there is no role for the silicone tube in maintaining patency of the released obstruction in simple CNLDO; this is expected as simple CNLDO does not carry any risk factors such as an unusual site of obstruction, tight obstruction or anatomical variations. In complex CNLDO, the success rate of probing has significantly declined from 94.2% in simple obstruction to 47.4% (p=<0.001). Unlike probing, bicanalicular silastic intubation sustained high success rates (from 90.9% in simple obstruction to 85.2%; p=0.419), despite the complex variety of CNLDO. Moreover, the only statistically significant difference in the outcomes between probing and bicanalicular silastic intubation was attributed to the type of obstruction, and none of the preoperative characteristics was a risk factor for failure. These outcomes indicate that the silicone tube has a role in maintaining patency of the released obstruction in complex CNLDO. Due to small numbers when complex CNLDO cases were divided up, the most likely anatomical sites to derive benefit from intubation were common canalicular stenosis with lower end NLD obstruction and thick membrane at the lower end of NLD.

Our outcomes concur with previous prospective studies that have shown high success rates for probing with simple CNLDO and low success rates with complex CNLDO. For example, Kushner's study reported 100% and 36% success rates for probing in children with simple and complex obstructions, respectively.17 Kashkouli et al12 reported 90.2% and 33.3% success rates for probing in eyes with simple and complex obstructions, respectively. Honavar et al also reported success rates of 89.1% and 21.4% for probing in children younger than 9 years with simple and complex obstructions, respectively.16 However, the Paediatric Eye Disease Investigator Group (PEDIG) did not find complex CNLDO as a risk factor for probing. They reported success rates of 78% and 77% for probing in eyes with simple and complex obstructions, respectively.10

Age is considered a risk factor by many authors as the success rate declines after 2 years of age.2 ,8 ,9 ,12 ,20 However, other studies,1 ,3 ,10 including ours, did not consider age as a risk factor for probing. Of note, some practitioners may tend to treat older children by performing intubation because of a reported higher rate of probing failure in this age group. The older age group in our study has not shown statistically different outcomes between probing and bicanalicular silastic intubation. Some authors consider bilateral CNLDO a poor prognostic factor as it might be a harbinger of significant anatomical variation or nasal problems that cannot be successfully addressed with probing.2 ,10 ,20 Our study outcomes differ from the aforementioned reports as we found success rates of 88.5% and 96.2% for probing and bicanalicular silastic intubation, respectively, in bilateral cases (p=0.298). This might be due to the specific inclusion criteria dealing with only NLD obstruction and excluding other risk factors such as Down syndrome.22

Despite remarkable advancement in the material used for intubation, including greater biocompatibility and well tolerated silicone material, complications are still reported.23 Complications include tube dislodgement, punctal erosion, slit canaliculus due to ‘cheese-wiring’, conjunctival irritation and infection, corneal abrasion, tube breakage, granuloma formation, epistaxis, and even sinusitis.23 This is why we do not simply intubate all patients and end this debate. Different silicone tube designs with comparable success rates have been developed to overcome some of the aforementioned complications and to facilitate tube removal such as monocanalicular intubation.24 In our study tube dislodgement occurred in nine eyes, despite successful results, and slit canaliculi in one eye, which was considered a failure. As bicanalicular intubation has been used in this study, it leaves open the question of whether the use of monocanalicular intubation would avoid tube dislodgment and slit canaliculus. It should be mentioned that probing is not free from complications such as punctal bleeding and slit canaliculus from vigorous dilation or even false passage.10 ,25 However, such complications are prone to occur with intubation as probing is a preliminary step which must be done before silicone tube placement in any intubation procedure.

The prospective nature, randomisation and masked outcome evaluation strengthen our data; however, our study has some limitations due to small sample size and lack of nasal endoscopic guided probing. The small sample size of many of the baseline characteristics could cause p values to be non-significant. As probing is a blind procedure, the level and type of CNLDO in our series depended mainly on the surgeon's fingertip feelings during the advancement of the probe through the lacrimal drainage system. Some variants of complex CNLDO at the lower end of the NLD which derive benefit from intubation could have been treated successfully with probing if it was performed under endoscopic guidance. For example, thick membrane at the lower end of the NLD and submucosal track of the NLD might represent false passage that had not been detected. Moreover, our appreciation of tight CNLDO could be due to actual NLD stenosis or because we had been through a false passage. This is why a relatively increasing number of studies which highlight the value of using nasal endoscopy during probing have been published in recent years.25 ,26

In summary, the data here indicate that primary silastic intubation would appear unnecessary as a treatment of simple CNLDO in children below 6 years of age, but it seems to have a role in achieving successful outcomes in complex CNLDO. However, further prospective, randomised, comparative studies are warranted to reach a consensus on procedure selection.



  • Contributors YHA-F was responsible for study design, evaluated the patients preoperatively, performed surgical intervention, monitored data collection and completed the manuscript; AM was in charge of sample size calculation and statistical analysis; HK was responsible for postoperative evaluation of all patients; AA, HA and AHS evaluated the patients preoperatively, performed surgical intervention and data collection. All authors read and approved the final manuscript.

  • Competing interests None.

  • Patient consent Obtained.

  • Ethics approval Ethics approval was provided by the Institutional Review Board, Ophthalmology Department, College of Medicine, King Saud University.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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