Congenital nasolacrimal duct obstruction is widely recognized as the most common congenital anomaly of the lacrimal drainage system.¹ Conservative treatment remains the first-line approach during infancy and typically includes Crigler massage, along with topical antibiotics when clinically indicated.⁸,⁹ However, after 12-18 months of age, the condition becomes less responsive to massage alone, with probing being the next step in the plan of management, which can be performed via a blind or endoscopically guided approach. This article reviews the pros and cons of both approaches.

Literature Search Strategy A structured literature review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Electronic databases, including PubMed, Scopus, Web of Science, Embase, and Google Scholar, were searched for studies published between January 1980 and December 2025. The search terms included: • "Congenital nasolacrimal duct obstruction." • "CNLDO" • "Blind probing." • "Endoscopic-guided probing." • "Endoscopic-assisted probing." • "Pediatric nasolacrimal duct obstruction." • "Revision probing." • "Lacrimal drainage surgery." Boolean operators (AND, OR) were applied to refine the search strategy. Inclusion Criteria • Studies involving pediatric patients diagnosed with CNLDO. • Comparative studies evaluating blind probing and/or endoscopic-guided probing. • Prospective studies, retrospective studies, cohort studies, and systematic reviews. • Articles published in English. Exclusion Criteria • Adult lacrimal obstruction studies. • Case reports involving fewer than five patients. • Conference abstracts without full text. • Duplicate publications. PRISMA Flow Summary Records identified through database searching: n = 432 Additional records identified through reference screening: n = 28 Total records identified: n = 460 Records after duplicate removal: n = 378 Records screened by title and abstract: n = 378 Full-text articles assessed for eligibility: n = 72 Studies excluded after full-text review: n = 47 Studies included in qualitative synthesis: n = 25 Studies included in comparative analysis: n = 15

Epidemiology and Pathophysiology

Congenital nasolacrimal duct obstruction is widely recognized as the most common congenital anomaly of the lacrimal drainage system.¹ The incidence of Congenital nasolacrimal duct obstruction varies between 5% and 20% in neonates, reflecting its relatively frequent occurrence in early infancy.² The underlying pathophysiology is most commonly attributed to the failure of canalization at the level of the valve of Hasner, resulting in distal nasolacrimal duct obstruction.³ (Table 1)

Table 1: Frequencies of the site of obstruction

A substantial proportion of affected infants experience spontaneous resolution, with studies reporting natural recovery in approximately 50% to 90% of cases within the first year of life.³,⁸ This high rate of spontaneous improvement forms the basis for initial conservative management in early infancy. (Table 2)

Table 2: Comparative Success Rates by Clinical Scenario

Natural History and Conservative Management

Conservative treatment remains the first-line approach during infancy and typically includes lacrimal sac massage, commonly referred to as Crigler massage, along with topical antibiotics when clinically indicated.⁸,⁹ This approach is associated with favorable outcomes, particularly in younger infants. However, the likelihood of spontaneous resolution decreases with increasing age, and delayed intervention beyond 12 to 18 months has been associated with reduced success rates of subsequent probing procedures.⁴,¹⁰

Evolution of Surgical Management

Nasolacrimal duct probing has remained the cornerstone of surgical management for CNLDO since its initial description by Bowman in the 19th century.¹¹ Traditional blind probing relies primarily on tactile feedback to navigate the nasolacrimal system and perforate the obstructing membrane. In contrast, endoscopic-assisted probing, introduced in the 1990s, allows direct visualization of the inferior meatus and distal nasolacrimal duct, thereby improving procedural accuracy and safety.⁶,¹²,¹³

Anatomy and Pathophysiology

The most common site of obstruction in CNLDO is the valve of Hasner, accounting for approximately 80% to 90% of cases.²,³ Less frequently, obstruction may occur at proximal segments of the lacrimal drainage system, including the canaliculi or common canaliculus, and such cases are generally associated with poorer surgical outcomes and higher failure rates.¹⁴

Additionally, anatomical variations within the nasal cavity, particularly inferior turbinate hypertrophy, have been implicated in failed probing procedures and may contribute to persistent obstruction or technical difficulty during surgery.⁶,¹⁵

Surgical Techniques

Blind Probing

Conventional blind probing involves the passage of a Bowman probe through the punctum and canalicular system into the nasolacrimal duct to mechanically disrupt the distal membranous obstruction.⁴,¹¹

The procedure is performed under general anesthesia or, in select cases in infants under 6 months, under topical anesthesia with restraint (office probing).

Procedural steps:

1. Punctal dilation — The superior or inferior punctum is dilated using a punctal dilator
2. Probe insertion — A Bowman probe (typically size 0 or 00) is introduced through the punctum vertically for 2 mm, then rotated horizontally and advanced along the canaliculus
3. Sac entry — The probe encounters a hard stop at the medial wall of the lacrimal sac, confirming entry
4. Duct navigation — The probe is rotated superiorly and advanced inferiorly, posteriorly, and laterally through the nasolacrimal duct
5. Membrane rupture — A "give" or "pop" is felt as the obstructing membrane is perforated
6. Confirmation — Saline irrigation through the canaliculi with recovery from the nose confirms patency

 The success of the procedure is typically confirmed by irrigation and visualization or retrieval of fluid from the nasal cavity.³ Although widely practiced, this technique relies heavily on the surgeon's experience and tactile feedback, which introduces variability in outcomes.

Endoscopic-Guided Probing

Endoscopic-guided probing employs rigid nasal endoscopy, typically at 0° or 30°, to directly visualize the inferior meatus during probe passage.⁶,¹²

Equipment required:

• Rigid nasal endoscope (0° or 30°, 2.7 mm diameter)
• Light source and camera system
• Standard probing instruments
• Nasal decongestant spray
• Suction apparatus

Procedural steps:

1. Nasal preparation — Topical decongestant (oxymetazoline) and, optionally, mucosal vasoconstrictor application
2. Endoscopic examination — Initial nasal endoscopy to assess inferior meatus anatomy, identify turbinate hypertrophy or other pathology
3. Probing — Standard probing technique is initiated while an assistant maintains endoscopic visualization of the inferior meatus
4. Visual confirmation — The probe tip is observed tenting and then penetrating the membrane at the valve of Hasner
5. Concurrent treatment — If turbinate hypertrophy or other nasal pathology is identified, appropriate intervention (infracture, marsupialization) is performed
6. Irrigation verification — Fluorescein-stained saline irrigation with endoscopic visualization of egress

This technique enables real-time confirmation of probe entry into the nasal cavity and allows identification of anatomical abnormalities that may contribute to obstruction.⁶,¹³ The enhanced visualization provided by this method significantly improves procedural precision and reduces the risk of incorrect probe placement.

Clinical Outcomes

Success Rates

The success of blind probing is known to be highly dependent on patient age, timing of intervention, and anatomical complexity of the obstruction.³,⁴,¹⁰ In contrast, endoscopic-assisted techniques demonstrate more consistent outcomes across different age groups and are particularly advantageous in older children and revision cases.⁵,⁶,¹³

In infants younger than 12 months, success rates for blind probing range from 85% to 95%, whereas endoscopic-guided probing achieves success rates of 92% to 98%.³,⁵ Between 12 and 24 months of age, blind probing success decreases to approximately 70% to 85%, while endoscopic approaches maintain higher success rates of 88% to 95%.⁴,⁶ In children older than 24 months, the difference becomes more pronounced, with blind probing achieving only 50% to 70% success compared to 80% to 92% with endoscopic assistance.⁵,¹⁰ In revision cases, endoscopic probing clearly outperforms blind techniques, with success rates of 85% to 93% compared to 50% to 65%.⁶,¹³ (Table 2)

Factors Influencing Outcome

Several factors influence the success of probing procedures. Increasing age at the time of intervention, complex anatomical obstruction, and prior failed probing have all been consistently associated with reduced success rates.³,¹⁰ The use of endoscopic guidance mitigates several of these challenges by allowing direct visualization of the obstruction site and improving procedural accuracy.⁶,¹²

Advantages of Endoscopic-Guided Probing

Endoscopic-guided probing offers several important clinical advantages over the conventional blind technique. The most significant benefit lies in the ability to directly visualize the anatomical pathway during the procedure, thereby enhancing accuracy and reducing reliance on tactile feedback alone.⁶,¹²

Furthermore, endoscopic visualization significantly reduces the incidence of false passage formation, a recognized complication of blind probing that occurs in approximately 2% to 8% of cases.⁴,¹¹ In addition, this approach enables the identification of associated nasal pathologies such as inferior turbinate hypertrophy, mucosal cysts, and septal deviation, all of which may contribute to persistent obstruction.¹⁵,¹⁶

In complex and recurrent cases, particularly in older children, endoscopic techniques have demonstrated superior outcomes and improved long-term success rates.⁵,⁶,¹³

Disadvantages

Despite its advantages, endoscopic-guided probing is associated with certain limitations. The procedure requires specialized equipment and additional surgical training, which may not be available in all clinical settings.¹³,¹⁷. Furthermore, operative time is modestly increased, typically by 5 to 15 minutes compared with blind probing.⁶ (Table 3) Financial cost and limited accessibility remain important barriers to widespread adoption, particularly in resource-limited environments.¹⁷

Table 3: Comparative Operative Times

Complications

Complications associated with nasolacrimal duct probing are generally minor and may occur with either technique. These include epistaxis, canalicular trauma, and transient postoperative edema.³,¹⁴

Blind probing carries a specific risk of false passage formation, reported in approximately 2% to 8% of cases, as well as incomplete ductal entry.⁴,¹¹

Endoscopic-guided probing, while generally safer in terms of anatomical accuracy, may still be associated with minor complications such as turbinate trauma, mucosal laceration, and, rarely, synechiae formation within the nasal cavity.⁶,¹³,¹⁵

Cost-Effectiveness

Although endoscopic techniques are associated with higher initial procedural costs, their improved success rates and reduced need for revision procedures contribute to better long-term cost-effectiveness, particularly in older children and complex cases.³,¹⁷

Clinical Recommendations

Current evidence suggests that blind probing remains an appropriate first-line intervention for infants younger than 12 months with uncomplicated CNLDO.³,⁸ (Table 4)

Table 4. Comparison of Key Studies Evaluating Blind and Endoscopic-Guided Probing in CNLDO

In contrast, endoscopic-guided probing is recommended in cases involving recurrent obstruction, children older than 18 to 24 months, and in patients with suspected or documented nasal pathology contributing to obstruction.⁴,¹⁰,¹⁵

Endoscopic-guided probing represents a meaningful advancement in the management of congenital nasolacrimal duct obstruction, offering superior visualization and improved outcomes in selected patient populations.¹,⁶,¹³ Nevertheless, conventional blind probing continues to remain an effective, safe, and widely utilized treatment option for early uncomplicated cases, particularly in infants.³,⁸