The Agreement Between Syringing, Dacryocystography, and Dacryoendoscopy Findings in Lacrimal Duct Obstruction

doi:10.21203/rs.3.rs-1966740/v1

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Research Article

The Agreement Between Syringing, Dacryocystography, and Dacryoendoscopy Findings in Lacrimal Duct Obstruction

https://doi.org/10.21203/rs.3.rs-1966740/v1

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published 02 May, 2023

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Purpose

We retrospectively investigated the agreement of the diagnostic findings of syringing, dacryocystography (DCG), and dacryoendoscopy in the obstruction of the lacrimal drainage system (LDS).

Methods

We examined 113 patients (211 LDS) who underwent syringing, DCG, and dacryoendoscopy for preoperative evaluation of LDS obstruction. Obstruction was compared by classifying the grade and the site of obstruction into three levels, respectively. The diagnostic agreement between the tests was assessed by determining the weighted Kappa value.

Results

25 male (49 LDS) and 88 female patients (162 LDS) were included in this study. LDS obstruction was observed in 77.4% of the cases by syringing, 60.0% by DCG, and 81.3% by dacryoendoscopy. Regarding the agreement in the obstruction grade, Cohen's Kappa value for DCG and dacryoendoscopy was 0.65 (95%CI: 0.56–0.74). Meanwhile, the DCG and dacryoendoscopy showed consistency in the site of obstruction in 77.9% of the cases. DCG found no obstruction in 38.4% of all cases, whereas 47.9% of them showed stenosis or obstruction by dacryoendoscopy. When discrepancies were observed between syringing and dacryoendoscopy to detect the site of obstruction, the combination of syringing and DCG reached the dacryoendoscopy findings at the 99% level.

Conclusions

"Substantial" agreements were found between the diagnostic findings of the three examinations. Among them, the highest agreement was between syringing and dacryoendoscopy in determining the site of obstruction. The lowest agreements were between syringing and DCG in diagnosing the grade and the site of obstruction.

Ophthalmology

Epiphora

Lacrimal drainage system obstruction

Lacrimal syringing

Dacryocystography

Dacryoendoscopy

Weighted Kappa value

The lacrimal drainage system (LDS) extends from the lacrimal punctum to the lower opening of the nasolacrimal duct on the lateral wall of the inferior nasal meatus. Lacrimal fluid passes through the upper and lower puncta, the superior and inferior canaliculi, and the common canaliculus to reach the internal common punctum on the lacrimal sac. Then the lacrimal outflow pathway leads to the lacrimal sac and nasolacrimal duct. Obstruction of the LDS can develop at any level along the lacrimal outflow pathway: at the punctum, canaliculus, lacrimal sac, nasolacrimal duct, and nasal ostium.¹ The pathophysiology of the LDS obstruction remains unclear; it is proposed that descending inflammation from the eyes or ascending inflammation from the nose provokes inflammation of the mucosal membrane of the lacrimal duct. Then the inflammation causes mucosal membrane swelling and remodeling of the connective tissue, leading to subepithelial cavernous body dysfunction with reactive hyperemia—resulting in temporary obstruction of the lacrimal outflow pathway. ²

Obstruction of the LDS is generally diagnosed by using lacrimal syringing, probing with a lacrimal bougie, and dacryocystography to determine the degree and the site of obstruction. Syringing is a practical test in evaluating lacrimal outflow obstruction and provides valuable information on the presence, localization, and nature of the obstruction. Syringing can evaluate whether the canaliculus, lacrimal sac, and nasolacrimal duct are qualitatively patent, stenotic, or obstructed. However, because syringing is performed with higher water pressure than the normal tear flow, it is difficult to evaluate the physiological lacrimal flow dynamics; therefore, syringing is unsuitable for evaluating functional epiphora.³

Dacryocystography (DCG) has played a central role in diagnosing lacrimal duct obstruction since Ewing first reported for contrasting the LDS in the early 20th century.^4,5 DCG is a classic and valuable test and remains the primary method to evaluate the lacrimal outflow obstruction. DCG is practical in detecting the localization of obstructed areas in lacrimal passage. The basic idea of DCG is to find the site where the contrast agent is first occluded and to diagnose that area as the obstruction level. The level of lacrimal passage obstruction is classified into presaccal obstruction, in which the contrast agent does not reach the lacrimal sac, and postsaccal obstruction, in which the contrast agent does reach the lacrimal sac. Since its application in dentistry, cone-beam CT (CBCT) has gradually been applied clinically in the head and neck region. It is widely used in medical facilities for dentistry, oral surgery, and otorhinolaryngology. ^6–9 Despite the limited reports on CBCT examinations in ophthalmology, CBCT-DCG reported by Tschopp et al. has several advantages that it can be performed with only one-tenth the radiation exposure compared to conventional multi-slice CT-DCG.^10,11 CBCT-DCG is also valuable for evaluating lacrimal outflow obstruction because it can be performed in the seated position and can investigate physiological lacrimal drainage dynamics.

Dacryoendoscopy is one of the examinations that have developed rapidly in recent years. With the growing use of the dacryoendoscope and advances in the fiber-optic system, the use of the dacryoendoscope for diagnosing lacrimal outflow obstruction is increasing.¹² Especially in East Asia, including Japan, Korea, and the Philippines, the diagnosis and treatment of lacrimal outflow obstructions with dacryoendoscope have increased remarkably over the past two decades.^13–16 East Asians have relatively flat facial features, with a less elevated superior orbital rim than other ethnic groups. This may allow for relatively easy manipulation of a dacryoendoscope.¹⁷ Another contribution is that the development of bent-tip and curved probes has made it possible to observe all the way to the end of the nasolacrimal duct in cases that were difficult to observe with the conventional straight-type probes (Fig. 1). As the first generation of lacrimal endoscopes, Cohen et al. introduced the dacryoscopy in 1979.¹⁸ In this method, a rigid tube was equipped with a lens at the tip and inside. The inspector viewed the lumen directly through the lens. The dacryoscopy was a relatively large device, so the inspector inserted a dacryoscopy from one punctum and a light source from the other punctum to observe the lacrimal passage. As the second generation of lacrimal endoscopes, Ashenhurst and Hurwitz's canaliculoscope was introduced in 1991, and Fein's endoscopy of the lacrimal outflow system was introduced in 1992. These were all flexible fiber endoscopes.^19,20 As the third generation of lacrimal endoscopes, Emmerich's rigid fiber endoscope (dacryoendoscope) was developed in 1997, and a bent-type rigid fiber endoscope was developed in Japan in 2002.^21,22 These third-generation lacrimal endoscopes are distinctive in that a rigid probe covers the tip of the second-generation flexible lacrimal endoscope. Moreover, they are equipped with a channel for water irrigation, a laser probe, or a micro-drill to enable microsurgery in the lacrimal duct. Because of its shape, the Japanese bent-type endoscope can easily be inserted into the nasolacrimal duct and reach the opening on the inferior nasal meatus. However, because the probe is bent, it cannot be equipped with a laser or micro-drill. The recanalization surgery using a bent-type endoscope involves perforating the obstructed site by pushing a catheter capped on the probe's tip and placing a silicone tube stent in the opened lacrimal pathway.^{14–16, 23,24}

The consistency of diagnostic results from various examination methods of the LDS is an important question that needs to be investigated. Then, we retrospectively reviewed the medical records of 113 patients who underwent syringing, DCG, and dacryoendoscopy for preoperative evaluation of obstruction of the LDS. We investigated the agreement of the diagnostic results regarding the degree of the obstruction and the site of obstruction of the lacrimal outflow pathway between these three types of examinations.

Patient Selection

The protocol and consent forms for the study were approved by the Institutional Review Board of Ehime University (Ethical approval No. 1601003). The research was recorded with the University Hospital Medical Information Network Clinical Trials Registry (UMIN 000025180). Each patient provided documented informed consent before registration. All procedures used in this study were performed under the tenets of the Helsinki Declaration.

This study included 113 patients (211 sides) who underwent syringing, DCG, and dacryoendoscopy for preoperative evaluation of the lacrimal outflow obstruction at Ehime University Hospital from January 2021 to March 2022. The examinations were performed by three ophthalmologists (TK, AM, and AS) with 10, 4, and 14 years of experience in dacryoendoscopic operation, respectively. The degree of lacrimal duct obstruction and the site of lacrimal duct obstruction, as diagnosed by the three examinations, were compared retrospectively. The degree of obstruction was evaluated in three levels: no obstruction, stenosis, and obstruction. The site of obstruction was classified into three types: no obstruction, presaccal obstruction, and postsaccal obstruction. The agreement between the tests was assessed by calculating the kappa coefficient. We excluded patients who had a history of systemic chemotherapy with 5-fluorouracil, docetaxel, or idoxuridine from the statistical analysis. Patients with a history of radiation therapy to the cranial region or posttraumatic bone deformity were excluded from this study. Patients with previous lacrimal duct surgery, such as recanalization surgery or dacryocystorhinostomy (DCR), were also excluded; hence, all patients were evaluated preoperatively for initial surgery for the obstruction of the lacrimal outflow obstruction.

Lacrimal syringing (Syringing)

If the punctum were small, they were dilated using a punctum dilator. Saline was injected through the upper and lower punctum using a 23-gauge cannula and investigated if it reached the nasal cavity. If the saline did not reach the nasal cavity, it was considered an anatomic obstruction of the LDS. Resistance during the syringing and the presence of reflux and its properties were checked. Partial irrigation into the nasal cavity with some extent of reflux was considered incomplete obstruction (stenosis). When serous reflux material was observed, obstruction of canaliculus, common canaliculus, or upper lacrimal sac was considered. When viscous reflux material was observed, obstruction at distal sites such as the lacrimal sac or nasolacrimal duct was considered. The communication between the upper and lower canaliculus was also checked. Reflux from the punctum opposite to the injecting side was considered obstruction of the common canaliculus or more distal site. Direct reflux of saline from the injecting punctum was considered the obstruction of the canaliculus.²⁵

Dacryocystography (DCG)

Patients with acute dacryocystitis, allergy to contrast media or iodine were excluded from the examination. After topical anesthesia with 4% lidocaine instillation, the lacrimal pathway was washed with saline before the examination. The contrast agent utilized was a nonionic, water-soluble agent (1–2 mL; Omnipaque 300 [iohexol]; GE Healthcare, Tokyo, Japan). The contrast agent was manually injected slowly through the upper and lower punctum until the patient reported that the solution reached the nasal antrum or until the contrast agent flowed back from the punctum. We performed bilateral DCG to examine unaffected sides with one-sided lacrimal outflow obstruction. Image capture was performed with CBCT within 10 min after injection of the contrast medium. CBCT-DCG images were acquired using a 3D Accuitomo F17 (Morita, Kyoto, Japan). The imaging conditions were a scan time of 17.5 s and X-ray output of 90 kV and 8.0 mA. Image manipulation was made using dedicated computer software (i-Dixel 2.0; Morita, Kyoto, Japan). The DCG images were converted to monochrome to facilitate observation of the contrast media.

Dacryoendoscopy

Patients with acute dacryocystitis were excluded as an indication for endoscopy. The patient was supine on the procedural bed, and topical ocular surface and lacrimal duct anesthesia were applied with 4% lidocaine. Subcutaneous infiltration anesthesia around the punctum and inner canthus was added with 2% lidocaine with epinephrine as needed. If necessary, the punctum was dilated with a punctum dilator, and a bent-type rigid dacryoendoscope (CK-10, Fibertech, Tokyo) was inserted through the upper and lower punctum. While irrigating with saline through the water channel, the probe passed through the canaliculus and common canaliculus, reaching the lacrimal sac from the internal common punctum. Then the probe was rotated 90° inferiorly to view the lacrimal sac, nasolacrimal duct, and nasolacrimal duct opening (Video 1). In patients with lacrimal passage obstruction, the site, grade, and characteristics of the obstructed area were recorded. In the preoperative endoscopic examination, we did not touch or puncture the site of the obstruction but only observed it.

Statistical Analysis

An inter-rater reliability analysis was performed between the dependent samples of two kinds of examinations, i.e., Syringing and DCG, Syringing and dacryoendoscopy, and DCG and dacryoendoscopy. For this purpose, Cohen's Kappa was calculated, a measure of the agreement between two dependent categorical samples. Furthermore, an inter-rater reliability analysis was performed between the dependent samples of three examinations: Syringing, DCG, and dacryoendoscopy. For this purpose, the Fleiss Kappa was calculated, a measure of the agreement between more than two dependent categorical samples. For the interpretation of the calculated Kappa coefficient, the table of Landis and Koch was used as a guide (Table 1)²⁶. All statistical analyses were performed online statistics calculator DATAtab (Graz, Austria. URL https://datatab.net)

The mean age of the patients was 71.3 years (SD = 13.7). 25 male patients (49 lacrimal pathways) and 88 female patients (162 lacrimal pathways) were included in this study. The mean duration of preoperative obstruction was 19.1 months (SD = 52.7). The duration of preoperative obstruction was denoted based on the duration of chronic epiphora as described in the patient's questionnaire.

Agreement of the examinations regarding the grade of obstruction

The number of cases regarding the grade of obstruction diagnosed by Syringing, DCG, and Dacryoendoscopy is listed in Table 2. The agreement in diagnosing the grade of obstruction of the three examinations: Syringing, DCG, and Dacryoendoscopy is listed in Table 3. Fleiss' kappa coefficient for the diagnosis of degree of obstruction for the three tests was 0.61 (SE = 0.03, 95% CI = 0.55 - 0.67, p < 0.001). According to the Landis and Koch’s classification shown in Table 1, the agreement between the three examinations was "Substantial."

Syringing and DCG

The Cohen's Kappa value of concordance between the two tests, Syringing and DCG, for the agreement in diagnosing the grade of obstruction was determined to be κ = 0.55 (SE = 0.05, 95% CI = 0.46 - 0.65, p < 0.001), which indicated a "Moderate" agreement (Table 3 and Supplementary Table 1). A total of 194 diagnoses of Syringing and DCG were examined, and the agreement of no obstruction, stenosis, and obstruction in the two tests was 44, 21, and 73 cases, respectively. Overall, the percentage of Syringing and DCG diagnoses consistent with each other was 71.1%. In contrast, 19 cases (17.5%) diagnosed as stenosis and 15 cases (17.5%) diagnosed as obstruction by Syringing were diagnosed as no obstruction by DCG, indicating a discrepancy between the two diagnoses. The composition of the 19 cases diagnosed with no obstruction by DCG and stenosis by Syringing was common canalicular stenosis (CCS) in 7 cases, dacryolith in 3 cases, and punctum stenosis in 2 cases, and no obstruction in 3 cases, when reviewed according to the dacryoendoscopic findings. Also, the composition of the 15 cases diagnosed with no obstruction by DCG and obstruction by Syringing was CCS in 5 cases, common canalicular obstruction (CCO) in 4 cases, and dacryolith in 1 case, when reviewed by dacryoendoscopic findings.

Syringing and Dacryoendoscopy

A total of 207 diagnoses of Syringing and Dacryoendoscopy were examined, and the agreement of no obstruction, stenosis, and obstruction in the two tests was 35, 38, and 88 cases, respectively. The Cohen's Kappa value of concordance between the two tests, Syringing and Dacryoendoscopy, for the agreement in the grade of obstruction was determined to be κ = 0.65 (SE = 0.05, 95% CI = 0.56 - 0.74, p < 0.001), which indicated a "substantial" agreement (Table 3 and Supplementary Table 2). Overall, the percentage of Syringing and Dacryoendoscopy diagnoses matched was 77.8%. Meanwhile, 10 cases (4.8%) diagnosed with no obstruction by Syringing were diagnosed as stenosis by Dacryoendoscopy, indicating a discrepancy between the diagnoses of the two examinations. The composition of these 10 cases was CCS in 3 cases, nasolacrimal duct stenosis in 4 cases, lacrimal sac stenosis in 2 cases, and dacryolith in 1case.

DCG and Dacryoendoscopy

The Cohen's Kappa value of the agreement between DCG and Dacryoendoscopy diagnoses was determined to be κ = 0.65 (SE = 0.05, 95% CI = 0.56 - 0.74, p < 0.001), indicating " Substantial" agreement regarding the diagnosis of the grade of obstruction (Table 3 and Supplementary Table 3). Assessment of the 190 diagnoses from both methods revealed 38, 37, and 70 cases of concordance for no obstruction, stenosis, and obstruction, respectively, and overall, the percentage of agreement between DCG and Dacryoendoscopy was 76.3%. In contrast, DCG results showed 35 cases of no obstruction, in which Dacryoendoscopy diagnosed stenosis in 27 cases (18.4%) and obstruction in 8 cases (18.4%), indicating a discrepancy in diagnostic results between the two examinations. The 27 cases diagnosed with no obstruction by DCG and stenosis by Dacryoendoscopy consisted of 16 cases of CCS, 4 cases of dacryolith, and 5 cases of postsaccal stenosis. In addition, 4 cases of canalicular obstruction and 3 cases of CCO were found in patients diagnosed with no obstruction by DCG and obstruction by Dacryoendoscopy.

Agreement of the examinations regarding the site of obstruction

The number of cases regarding the site of obstruction diagnosed by syringing, DCG, and Dacryoendoscopy is listed in Table 4. The agreement in diagnosing the site of obstruction of Syringing, DCG, and Dacryoendoscopy is listed in Table 5. Fleiss' kappa coefficient for the diagnosis of the site of obstruction for the three tests was 0.62 (SE = 0.03, 95% CI = 0.57 - 0.68, p < 0.001). According to the Landis and Koch’s classification shown in Table 1, the agreement between the three preoperative examinations to detect the site of obstruction was "Substantial."

Syringing and DCG

The Cohen's Kappa value of agreement between the two tests, Syringing and DCG, for the diagnosis of the site of obstruction was determined to be κ = 0.55 (SE = 0.05, 95% CI = 0.45 - 0.64, p < 0.001), indicating the "moderate" agreement (Table 5 and Supplementary Table 4). A review of 194 diagnostic results demonstrated 44, 28, and 62 concordances for no obstruction, presaccal obstruction, and postsaccal obstruction between the two examinations, respectively. Overall, the percentage of concordance between Syringing and DCG results was 69.1%. Meanwhile, a total of 51 cases (26.3%) diagnosed with presaccal obstruction by Syringing were diagnosed with no obstruction and postsaccal obstruction in 29 and 22 cases, respectively. That showed a discrepancy between the diagnoses of two examinations. The assessment of the 29 cases diagnosed with presaccal obstruction by syringing and no obstruction by DCG included 11 cases of CCS, 4 cases of CCO, 4 cases of canaliculus obstruction, and 5 cases of no obstruction when reviewed on dacryoendoscopy findings. The 22 cases diagnosed with presaccal obstruction by Syringing and postsaccal obstruction by DCG included 3 cases of CCO, 10 cases of lacrimal sac obstruction, and 7 cases of nasolacrimal duct obstruction, reviewed from dacryoendoscopic findings.

Syringing and Dacryoendoscopy

The Cohen's Kappa value of agreement between Syringing and Dacryoendoscopy for the diagnosis of the site of obstruction was determined to be κ = 0.7 (SE = 0.04, 95% CI = 0.62 - 0.78, p < 0.001), indicating "Substantial" agreement (Table 5 and Supplementary Table 5). A review of 207 diagnostic results identified 35, 65, and 67 cases of concordance between Syringing and Dacryoendoscopy for no obstruction, presaccal obstruction, and postsaccal obstruction, respectively. In total, the percentage of concordance between Syringing and Dacryoendoscopy diagnoses was 80.7%. In contrast, 20 cases (9.7%) were diagnosed with presaccal obstruction by Syringing but postsaccal obstruction by Dacryoendoscopy. These included 13 cases of stenosis or obstruction of the lachrymal sac, 6 cases of stenosis or obstruction of the nasolacrimal duct, and 2 cases of postsaccal dacryolith. There were 4 cases (1.9%) with presaccal obstruction diagnosed by Syringing but no obstruction on Dacryoendoscopy. 8 cases (3.9%) were diagnosed with postsaccal obstruction by Dacryoendoscopy, regardless of the absence of obstruction by Syringing. These 8 cases included 2 cases of lacrimal sac stenosis, 5 cases of nasolacrimal duct stenosis, and 1 case of dacryolith.

DCG and Dacryoendoscopy

The Cohen's Kappa value of concordance between DCG and Dacryoendoscopy results for the diagnosis of the obstructed site was determined to be κ = 0.66 (SE = 0.05, 95% CI = 0.57 - 0.75, p < 0.001), indicating "Substantial" agreement was found between these examinations (Table 5 and Supplementary Table 6). A total of 190 diagnoses were examined, concordance of no obstruction, presaccal obstruction, and postsaccal obstruction in DCG and Dacryoendoscopy in 38, 28, and 82 cases, respectively. The overall rate of concordance between DCG and Dacryoendoscopy diagnostic results was 77.9%. On the contrary, 28 cases (14.7%) were diagnosed with presaccal obstruction by Dacryoendoscopy, while DCG found no obstruction. Among them were 16 cases of CCS, 4 cases of CCO, 4 cases of canaliculus occlusion, and 1 case of canaliculus dacryolith.

In our current study, the highest agreement in the grade of obstruction was between Syringing and Dacryoendoscopy and DCG and Dacryoendoscopy. Both these Cohen's Kappa were 0.65 (95% CI: 0.56–0.74). On the other hand, Syringing and DCG had the lowest Kappa, 0.55 (95% CI: 0.46–0.65). A previous study by Bae et al. also reported the highest agreement between Dacryoendoscopy and DCG and the lowest agreement between Syringing and DCG, consistent with the overall trend of our results.²⁷ Regarding the agreement in the site of obstruction, the highest agreement was found between Syringing and Dacryoendoscopy, with a Kappa value of 0.7 (95% CI: 0.62–0.78). The lowest was Syringing and DCG, with a Kappa coefficient of 0.55 (95% CI: 0.45–0.64).

In general, the first line treatment for postsaccal obstruction is DCR. Various approaches have been proposed to treat presaccal obstruction, depending on whether the obstruction is proximal or distal and the extent of the obstruction. Cases of stenosis or incomplete occlusion are mainly treated with canalicular stenting and intubation. Meanwhile, if the obstruction is persistent and solid and reconstructive surgery is not feasible, a conjunctivodacryocystorhinostomy (CoDCR) using a Pyrex glass tube (Jones tube) will be selected. Thus, different surgical methods for presaccal obstruction are selected depending on the characteristics of the obstruction.^28,29 In LDS obstruction, an accurate diagnosis of the site of obstruction is essential to select the proper surgical method.

In our data, the diagnostic sensitivity and specificity for identifying presaccal obstruction in Syringing test were 89% and 82%, respectively. There were 20 of 207 cases (9.7%) in which the presaccal lesion was diagnosed by Syringing, albeit the postsaccal lesion was observed by dacryoendoscopy. Among them, 13 cases were due to stenosis or obstruction of the lachrymal sac, 6 were due to stenosis or obstruction of the nasolacrimal duct, and 1 was due to dacryolith formation. In these 20 cases, we examined whether DCG could diagnose the presence of a postsaccal lesion and found that the combination of Syringing and DCG could not diagnose the presence of a postsaccal lesion in only two cases. As a breakdown, there was a case of CCS diagnosed by Syringing and DCG, but stenosis in the middle of the lacrimal sac by dacryoendoscopy, and a case of CCO diagnosed by irrigation and DCG, but an obstruction in the upper part of the lacrimal sac by dacryoendoscopy. Collectively, the combination of Syringing and DCG was consistent with dacryoendoscopic findings in 99% of cases with presaccal lesions. Since DCG is insensitive to visualize canaliculus lesions due to the nature of the examination, presaccal lesions are better observed with a dacryoendoscope.^27,30

Also, the diagnostic sensitivity and specificity of Syringing to identify postsaccal obstruction in the current study were 71% and 95%, respectively. Syringing found lesions in the postsaccal, albeit dacryoendoscopy detected lesions in the presaccal region in 6 of 207 cases (2.9%). These included 2 cases of CCO and 4 cases of CCS. Two CCO lesions detected on dacryoendoscopy were also accurately diagnosed as CCO on DCG. However, the combination of Syringing and DCG did not lead to a diagnosis in 3 cases of CCS. Collectively, 98.6% of cases of presaccal lesions were concordant with dacryoendoscopic findings when Syringing and DCG were combined.

In diagnosing the grade of obstruction, Dacryoendoscopy detected stenosis in 10 (22.2%) of the 45 cases diagnosed with no obstruction by Syringing. In 2 of these 10 cases, stenosis was also confirmed by DCG, but in the remaining 8 cases, no obstruction was diagnosed. Hence, Dacryoendoscopy detected a level of stenosis that was difficult for either Syringing or DCG. One of the pitfalls of DCG is that it is often prone to missing stenosis. In 73 of 190 cases (38.4%), DCG diagnosed no obstruction, whereas 27 of these cases revealed stenosis and 8 had obstruction, for a total of 35 cases (47.9%) with LDS obstruction by Dacryoendoscopy. The breakdown of the 27 cases diagnosed as no obstruction by DCG but stenosis by Dacryoendoscopy included 16 cases of CCS, 4 cases of dacryolith, and 5 cases of stenosis of the lacrimal sac or nasolacrimal duct. The breakdown of the 8 cases diagnosed as obstruction included 4 cases of canaliculus obstruction and 3 cases of CCO. It should be noted here that there are often cases in which the Dacryoendoscopy showed a diagnosis of obstruction. However, the DCG demonstrated that the contrast medium reached the nasal cavity, and the lesion was diagnosed with stenosis. This means that even though the lesion appeared visually obstructed by Dacryoendoscopy, a contrast medium could pass through the site and was not anatomically obstructed. This suggests that the diagnosis of stenosis and obstruction may differ depending on the examination method, leading to a discrepancy between DCG and endoscopic diagnosis.

Dacryoendoscopy is an examination method that directly observes the lumen of the LDS. With advances in fiber optic systems, endoscopes in common use today offer image quality of 10,000 to 15,000 pixels. Since the lumen is observed in color, lesions such as inflammatory findings in the mucosa, granulation, foreign bodies, and dacryoliths can be visualized apparently. It is also possible to diagnose the level of stenosis that cannot be detected by syringing or DCG. In addition, since no radiation is used, there is no risk of radiation exposure to the patient. One of the limitations of dacryoendoscopy is that it is difficult to identify the dacryocyst-nasolacrimal duct transition while viewing from the lumen. On the other hand, DCG is superior in terms of determining the height of the postsaccal lesion since a lacrimal duct surrounded by bony nasolacrimal ducts can be identified as a nasolacrimal duct. Another limitation of endoscopic diagnosis is that when it is used only for preoperative examination, since the endoscopic probe is not advanced beyond the site of stenosis, the lesions beyond the stenosis are not accessible. In this regard, DCG can evaluate lesions of the luminal structures of the entire LDS. DCG is a practical examination that provides information on the bones and sinuses surrounding the LDS, which endoscopy cannot observe. It is preferable to evaluate DCG and dacryoendoscopy comprehensively, based on an understanding of their respective characteristics.

In conclusion, Syringing, DCG, and Dacryoendoscopy results performed preoperatively for LDS obstruction showed that both the grade and site of obstruction were in "substantial" agreement with Fleiss Kappa. Furthermore, a comparison of the agreement between each test showed that the highest agreement was found between Syringing and Dacryoendoscopy in determining the site of obstruction. On the other hand, the lowest agreement was between Syringing and DCG in determining the grade of obstruction and the site of obstruction.

Acknowledgments

The study was supported by the Japan Society for the Promotion of Science Postdoctoral Fellowship for Research Abroad (Kaitoku-NIH, #24112 to JN). The funding source had no role in the study design, data collection, analysis, publication decision, or manuscript preparation.

Conflict of interest

The authors declare that they do not have any competing interests. The authors are solely responsible for the content and writing of the paper.

Author contributions

JN contributed to the conception, data extraction, analysis, and drafting. TK, AM, and AS worked on the practical examinations, data extraction, interpretation of the results, and drafting. TK, AM, and AS provided statistical advice. NM and AS were responsible for the general management of the study and critically revised the protocol and main manuscript.

Data availability

The data sets analyzed during the current study are available from the corresponding author (JN) on reasonable requests.

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Table 1. Interpretation of the calculated Kappa coefficient.

Kappa value	Interpretation
> 0.8	Almost Perfect
> 0.6	Substantial
> 0.4	Moderate
> 0.2	Fair
0 - 0.2	Slight
< 0	Poor

Table 2. Number of sides concerning the grade of obstruction diagnosed by Syringing, DCG, and dacryoendoscopy

		Syringing	DCG	Dacryoendoscopy
Grade of obstruction	No obstruction	48	78	39
	Stenosis	46	41	77
	Obstruction	118	76	92
	Total	212	195	208

Table 3. The agreements in the preoperative examination diagnoses regarding the grade of obstruction

	n	Agreement in the grade of obstruction
	n	κ value	SE	95% CI	p value
Syringing, DCG, and Dacryoendoscopy *	189	0.61	0.03	0.55 – 0.67	<0.001
Syringing and DCG **	194	0.55	0.05	0.46 – 0.65	<0.001
Syringing and Dacryoendoscopy **	207	0.65	0.05	0.56 – 0.74	<0.001
DCG and Dacryoendoscopy **	190	0.65	0.05	0.56 – 0.74	<0.001

n represents the number of lacrimal pathways. * An inter-rater reliability analysis was performed between the dependent samples of Syringing, DCG, and Dacryoendoscopy. For this purpose, the Fleiss Kappa was calculated, a measure of the agreement between more than two dependent categorical samples. ** An inter-rater reliability analysis was performed between the dependent samples of two examinations. For this purpose, the Cohens Kappa was calculated, a measure of the agreement between two dependent, categorical samples.

Table 4. Number of cases regarding the site of obstruction diagnosed by Syringing, DCG, and dacryoendoscopy

		Syringing	DCG	Dacryoendoscopy
Site of obstruction	No obstruction	48	78	39
	Presaccal obstruction	91	30	73
	Postsaccal obstruction	73	87	96
	Total	212	195	208

Table 5. The agreements in the preoperative examination diagnoses regarding the site of obstruction

	n	Agreement in the site of obstruction
	n	κ value	SE	95% CI	p value
Syringing, DCG, and Dacryoendoscopy *	189	0.62	0.03	0.57 – 0.68	<0.001
Syringing and DCG **	194	0.55	0.05	0.45 – 0.64	<0.001
Syringing and Dacryoendoscopy **	207	0.7	0.04	0.62 – 0.78	<0.001
DCG and Dacryoendoscopy **	190	0.66	0.05	0.57 – 0.75	<0.001

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The Agreement Between Syringing, Dacryocystography, and Dacryoendoscopy Findings in Lacrimal Duct Obstruction

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