The present study highlights a clinically important limitation of conventional outcome assessment after endoscopic dacryocystorhinostomy: an anatomically successful DCR is not necessarily a functionally successful DCR.

In this series of 110 patients, anatomical success was achieved in 87%, confirming the overall effectiveness of eDCR. More importantly, however, 18.9% of anatomically successful procedures remained functionally unsuccessful.

This finding shifts the focus of DCR outcome assessment from a purely surgical question—whether the rhinostomy remains open—to a more clinically relevant question: whether effective tear drainage has actually been restored.

Anatomical success is not synonymous with clinical cure:

Success rates reported after eDCR vary substantially according to the endpoint used.

A systematic review by Leong et al. demonstrated generally favorable results after DCR but also emphasized considerable heterogeneity among studies in surgical technique and definitions of success [1]. Modern series similarly report success rates commonly between approximately 82% and 98%, depending on patient selection and outcome criteria [6].

The 87% anatomical success rate observed in our cohort therefore falls within the expected range of published experience.

However, anatomical success alone overestimates patient-perceived benefit.

Shams et al. specifically evaluated persistent epiphora after anatomically successful DCR and estimated that approximately 5–10% of patients may continue to experience tearing despite a patent lacrimal pathway [7]. Their multicenter study demonstrated that functional epiphora represents a genuine postoperative entity rather than simply undetected ostium closure.

Our observed proportion of functional failure was higher, reaching 18.9% among anatomically successful cases.

Interestingly, Sung et al. reported exactly the same magnitude—18.9% functional failure among anatomically successful eDCR procedures—in their analysis of the effect of age on surgical outcomes [8]. Their study also identified older age and diabetes mellitus as significant correlates of functional failure, strongly supporting the biological and clinical relevance of these factors.

Why can an open DCR remain symptomatic?
Tear drainage is not a passive phenomenon.

Anatomical patency permits tears to reach the nasal cavity, but efficient transport depends on a coordinated lacrimal pump.

Blinking generates complex pressure changes through contraction and relaxation of the orbicularis oculi muscle, while appropriate punctal positioning and eyelid-globe apposition permit tears to enter the canalicular system.

Consequently, a patient can have an entirely patent rhinostomy while remaining symptomatic because the pathway is open but functionally inefficient.

This concept provides a plausible explanation for the ocular adnexal abnormalities observed in our functionally unsuccessful patients.

Age as a determinant of functional failure:
Older age was significantly associated with functional failure in our cohort (P=0.024).

Age-related changes can affect virtually every component of the lacrimal drainage mechanism, including eyelid tone, punctal position, conjunctival anatomy, blink efficiency, and ocular surface homeostasis.

Sung et al. found that although anatomical success did not significantly differ between younger and older groups, functional success was significantly lower among older patients [8]. Older patients with functional failure also exhibited a greater prevalence of eyelid laxity.

Similarly, studies of DCR in elderly populations have suggested that anatomical success may remain high while symptomatic resolution becomes less predictable [11].

These findings suggest that age should not be considered a contraindication to eDCR. Rather, advanced age should trigger a more comprehensive preoperative functional assessment.

Eyelid laxity and conjunctivochalasis: overlooked determinants?
Our observation of frequent eyelid laxity and conjunctivochalasis among patients with functional failure is particularly important.

Eyelid laxity can reduce the efficiency of the lacrimal pump and alter punctal apposition.

Conjunctivochalasis may mechanically interfere with tear flow toward the punctum and can itself produce epiphora through ocular-surface irritation.

Consequently, persistent tearing following DCR may reflect an incorrect assumption that all preoperative epiphora originated exclusively from nasolacrimal duct obstruction.

Preoperative examination should therefore extend beyond lacrimal irrigation.

In elderly patients in particular, careful evaluation should include eyelid position and tone, punctal position, conjunctivochalasis, ocular surface status, and blink dynamics.

Diabetes mellitus and functional outcome:
Diabetes mellitus was significantly associated with functional failure (P=0.008).

This association has also been reported by Sung et al. [8].

Several mechanisms are biologically plausible, including microvascular dysfunction, impaired wound healing, chronic low-grade inflammation, altered epithelial repair, neuropathy, and age-related confounding.

However, because diabetes prevalence increases with age, its independent contribution is difficult to establish without comprehensive multivariable adjustment.

Accordingly, our findings support diabetes as a risk marker, but they should not be interpreted as demonstrating a direct causal mechanism.

Level of obstruction matters:
Another important observation concerns the anatomical level of lacrimal obstruction.

More proximal obstruction was associated with poorer functional prognosis.

This is consistent with the large study by Lee et al., which evaluated 769 external DCR procedures. Although anatomical success reached 98.8%, functional success was only 81.9%. Common canalicular obstruction increased the risk of functional failure by approximately 75%, while canalicular obstruction approximately doubled the risk [9].

These results are physiologically logical.

DCR is exceptionally effective at bypassing distal nasolacrimal duct obstruction, but it cannot fully compensate for impaired tear entry or transport through the canalicular system.

Thus, the more proximal the dysfunction, the less likely creation of a distal bypass alone is to restore normal tear drainage.

Surgical factors versus patient factors:
An intriguing feature of our results is the lack of significant association between functional outcome and several technical variables, including uncinectomy, middle turbinectomy, granulation, membranous obstruction, and intranasal synechiae.

This does not imply that surgical technique is unimportant.

On the contrary, technical failure remains a major cause of anatomical failure.

Recent analysis of revision eDCR has shown that inadequate lacrimal sac exposure, cicatricial closure of the ostium, and synechiae are prominent findings in failed procedures [12].

The distinction is therefore essential:

technical factors may primarily determine whether the rhinostomy remains anatomically patent, whereas patient-related factors may become increasingly important in determining whether an anatomically successful operation is also functionally successful.

The role of silicone intubation:
Silicone intubation remains one of the most debated aspects of eDCR.

A systematic review and meta-analysis of 12 randomized controlled trials encompassing 1,239 procedures reported an overall eDCR success rate of 91.9% and found no statistically significant difference between stented and non-stented procedures [13].

More recent evidence continues to examine this question, with differences according to endpoints and patient selection [14].

Our cohort underwent bicanalicular silicone intubation, but the available analysis did not demonstrate stent-related parameters as independent determinants of poor functional outcome.

This supports the concept that stenting cannot correct dysfunction originating from the eyelid, punctum, canalicular pump, or ocular surface.

A clinically useful classification of DCR failure:
Our findings support separating postoperative failure into two major phenotypes.

Type I — Anatomical failure
This includes:

• ostium closure;
• cicatricial stenosis;
• inadequate sac exposure;
• granulation;
• membranous obstruction;
• synechiae;
• canalicular obstruction.

In this phenotype, revision surgery directed at restoring anatomical patency may be appropriate.

Type II — Functional failure despite anatomical success:
This includes persistent epiphora despite a patent ostium and may be associated with:

• eyelid laxity;
• impaired lacrimal pump;
• punctal malposition;
• conjunctivochalasis;
• proximal canalicular dysfunction;
• ocular surface abnormalities;
• excessive tear production.

In this second phenotype, simply enlarging an already patent rhinostomy may fail to address the actual mechanism of tearing.

This distinction has direct therapeutic consequences.

Toward patient-centered assessment of DCR success:
Traditional surgical studies frequently define success according to endoscopic ostium visualization or lacrimal irrigation.

These remain indispensable measures of technical success, but they should not constitute the sole endpoint.

A more clinically meaningful postoperative evaluation should integrate:

1. anatomical ostium patency;
2. lacrimal irrigation or functional drainage testing;
3. patient-reported epiphora;
4. eyelid and punctal examination;
5. ocular-surface assessment;
6. need for additional lacrimal procedures.

Such a framework would distinguish technical success from patient success.

Our findings therefore argue for a conceptual transition from an ostium-centered model of DCR outcome toward a lacrimal-system-centered model.

Clinical Implications:
The results of this study have several practical implications.

First, elderly patients should undergo systematic assessment for eyelid laxity, punctal abnormalities, and conjunctivochalasis before eDCR.

Second, the anatomical level of obstruction should be clearly characterized because proximal disease may predict poorer functional benefit.

Third, diabetes mellitus should be considered when counseling patients regarding postoperative expectations.

Fourth, persistent epiphora after eDCR should not automatically be interpreted as restenosis.

Before revision surgery, the surgeon should determine whether the primary procedure has failed anatomically or functionally.

This distinction may prevent unnecessary revision of an already patent rhinostomy.

Strengths:
A strength of this study is the consecutive nature of the series, comprising 110 endoscopic DCR procedures performed over a 10-year period at a single tertiary referral centre with a uniform surgical protocol.

Another important strength is the deliberate distinction between anatomical and functional outcomes.

Rather than considering ostium patency alone, our analysis explores why some technically successful procedures remain clinically unsuccessful.

The evaluation of demographic, systemic, intranasal, lacrimal, and ocular adnexal factors further provides a multidimensional assessment of surgical outcome.

Limitations:
Several limitations should be acknowledged.

First, the retrospective design introduces potential selection and information biases.

Second, standardized quantitative patient-reported epiphora scores were not available in the source dataset.

Third, detailed quantitative measurements of postoperative ostium size and dynamic lacrimal pump function were unavailable.

Fourth, several associations may be confounded by age, particularly diabetes mellitus and eyelid laxity.

Fifth, the available dataset does not provide all adjusted odds ratios and 95% confidence intervals required to construct a formal predictive model.

Finally, the sample size of 110 patients limits statistical power, particularly for the subgroup of anatomically successful procedures in which functional failure was assessed; non-significant associations should therefore be interpreted as inconclusive rather than as evidence of absence of effect, and the reported proportions carry correspondingly wide confidence intervals.

Future prospective studies should combine standardized anatomical assessment with validated epiphora scores, objective functional drainage testing, detailed eyelid examination, and multivariable predictive modeling.