Eye-Related Adverse Events After I-131 Radioiodine Therapy: A Systematic Review of the Current Literature.

OBJECTIVE: Although I-131 is relatively safe, there is limited focus on probable eye-related side effects after radioactive iodine (RAI) therapy. Thus, we aimed to provide evidence for the adverse outcomes of I-131, exclusively in patients with thyroid cancer. METHODS: A systematic review based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was designed to examine the ocular complications of RAI therapy. Databases including PubMed, Scopus, and Web of Science were searched until October 2023 with specific thyroid neoplasms, ophthalmology and iodine terms. After thorough screening and review, relevant data were extracted. RESULTS: The database search yielded 3434 articles, which resulted in the final 28 eligible studies. These studies investigated ophthalmic symptoms following RAI therapy, classifying them as obstructive diseases (for example, nasolacrimal duct obstruction; median incidence rate: 6.8%), inflammatory symptoms (median incidence rate: 13%), and cataracts (median incidence rate: 2.5 and 5%). The most common time interval between RAI therapy and the onset of symptoms was within the first 12 months and then declined in the preceding years. A strong positive correlation was observed between higher I-131 doses of more than 100 to 150 mCi (3.7-5.55 GBq) and the risk of symptom development. Ages older than 45 also showed a significant association with nasolacrimal duct obstruction. CONCLUSION: The risk of ophthalmic complications is associated with various factors, including the administration of high I-131 doses, age of more than 45 years, and time to event within the first 12 months. Considering these conditions may help enhance patient care and prevent adverse outcomes that may limit patients' quality of life.

Dacryolithogenesis or Dacryolithiasis-The Story So Far.

The term dacryoliths refers to the concretions found within the lacrimal system. When the term dacryoliths is unspecified, it usually refers to the noninfectious dacryoliths commonly isolated from the lacrimal sac and the nasolacrimal duct. More often, they are diagnosed incidentally during a dacryocystorhinostomy, and the reported incidence among all dacryocystorhinostomy surgeries is 5.7% to as high as 18%. Dacryolithiasis is a complex process occurring within the lacrimal system, and current evidence suggests a multifactorial etiology. The sequence of events can be summarized broadly into 4 stages: stage of susceptibility, stage of initiation/trigger, stage of development, and stage of maintenance. The triggering event is the breach of the lacrimal sac or nasolacrimal duct epithelium, resulting in microtrauma with blood leakage. The blood clots act as a nidus for subsequent sequential laying of mucopeptides, cellular debris present locally, debris washed from the ocular surface, and extraneous agents in tears. This process is aided by altered rheology and composition of the tear film. After the formation of dacryoliths, extracellular neutrophil traps usually form on the surface, which help to maintain the dacryoliths (which do not dissolve). This review highlights and discusses the possible sequence of events during dacryolithiasis.

Orbital Abscess Secondary to Nasolacrimal Duct Obstruction in an Extremely Preterm Infant.

Orbital abscesses are rarely encountered in children younger than 1 year. The literature is limited to isolated case reports and a few case series. Most such cases are reported in infants born at term, with the earliest reported gestational birth age at 34 weeks. Children are more prone to orbital cellulitis compared with adults due to their underdeveloped sinuses and immature immune systems, and the origin is most commonly an ethmoid sinus infection. Orbital cellulitis secondary to dacryocystitis is even less common, with only a few isolated cases reported in infants and children. Herein, the authors present a case of a large extraconal and intraconal orbital abscess secondary to nasolacrimal duct obstruction and dacryocystitis in an extremely preterm infant. We discuss the diagnosis and multidisciplinary management of this challenging case.

Nasolacrimal Duct Obstruction Secondary to Eosinophilic Chronic Rhinosinusitis: A Case Report.

A 47-year-old Japanese woman presented with a 1-year history of right-sided epiphora. On initial consultation, the patient had a high right tear meniscus height. CT images revealed bilateral soft tissue opacification in the nasal cavity and maxillary, frontal, and ethmoid sinuses. The lesion in the right nasal cavity and maxillary sinus involved the right lacrimal sac and nasolacrimal duct. Blood test results showed elevated eosinophil count. Endoscopic sinus surgery and excisional biopsy of the nasolacrimal duct were performed. Histopathological examinations of the excised right nasolacrimal duct and nasal polyps from the nasal cavity and maxillary sinus showed high levels of eosinophilic inflammatory infiltrates. The definite diagnosis of eosinophilic chronic rhinosinusitis was made, based on clinical, radiological, and histopathological findings. At 1.5-year follow-up, tear meniscus height was normal, the lacrimal drainage system remained patent, and the rhinosinusitis did not recur.

Canalicular Cyst After Punctal Plug Insertion.

This study describes the case of a patient with a canalicular cyst after punctal plug insertion. A 73-year-old male patient presented with a cystic mass on the right lower eyelid. He had undergone bilateral punctal occlusion with an absorbable punctal plug for dry eye syndrome 8 years ago. The lesion was palpable on the medial side of the right lower eyelid, accompanied by ectropion but without any inflammatory signs. Incision and drainage were performed, and a reduction in the size of the cystic mass was observed. Dacryocystography revealed cystic dilation of the right lower canaliculus, and a lacrimal probing test revealed right lower canalicular obstruction, leading to the diagnosis of a canalicular cyst. If a patient who has undergone punctal occlusion with punctal plugs presents with a mass in the medial canthus, a canalicular cyst should be considered in the differential diagnosis.

Medial lacrimal sac excision versus conventional H-shaped lacrimal sac opening in external dacryocystorhinostomy: a comparative cohort study.

PURPOSE: The external dacryocystorhinostomy (Ex-DCR) is a reliable but surgically challenging procedure to overcome a nasolacrimal duct obstruction (NLDO). The aim of this study is to describe the outcomes of a modified technique of lacrimal sac opening and to compare it with the conventional Ex-DCR. METHODS: This comparative cohort study included adult patients undergoing Ex-DCR for primary acquired NLDO by or under supervision of one surgeon. Group 1 (conventional Ex-DCR including H-shaped incision, anastomosis of the anterior mucosal flap to nasal mucosal flap and resection of the posterior sac flap) was compared with Group 2 (modified Ex-DCR including excision of the medial lacrimal sac and anastomosis of remaining anterior sac flap to nasal mucosal flap). Outcome measures included the success rate (defined as complete symptom relief or patent irrigation after three months), reoperation rate, redo-free survival within five years, and occurrence of postoperative bleeding and postoperative infection. RESULTS: 138 patients were included. The success rates were 94.7% (54/57 cases) for Group 1 and 96.3% (78/81) for Group 2 (p-value = 0.658). The redo-rate was 5.3% (3/75) in Group 1 and 2.5% (2/81) in Group 2 (p = 0.331). Two-year redo-free survival probability estimates were 89.8% for Group 1 and 96.3% for Group 2, respectively. No complications occurred in Group 2, whereas in Group 1, one patient (1.8%) suffered from postoperative bleeding and one (1.8%) from postoperative infection. CONCLUSIONS: This study showed that our modified Ex-DCR technique is equally efficacious compared with the conventional Ex-DCR technique in adult patients with NLDO.

Caruncle and plica hypertrophy causing mechanical secondary acquired lacrimal duct obstruction: - SALDO update study (SUP) - paper I.

PURPOSE: To exclusively report the clinical category of mechanical secondary acquired lacrimal duct obstruction (SALDO) secondary to the caruncle and plica hypertrophy. METHODS: Prospective interventional case series involving 10 consecutive eyes with megalocaruncle and plica hypertrophy were enrolled in the study. All patients presented with epiphora secondary to a demonstratable mechanical obstruction of the puncta. All patients underwent high magnification slit-lamp photography and Fourier-domain ocular coherence tomography scans (FD-OCT) of the tear meniscus height (TMH) pre- and post-operatively at 1-month and 3-months. Caruncle and plica size, position, and their relationship to the puncta were noted. All patients underwent partial carunculectomy. Primary outcome measures were demonstrable resolution of the mechanical obstruction of the puncta and the reduction in the tear meniscus height. The secondary outcome measure was the subjective improvement of the epiphora. RESULTS: The mean age of the patients was 67 years (range: 63-72 years). The average TMH was 843.1 (range: 345-2049) microns pre-operatively and 195.1(91-379) microns at 1-month follow-up. All patients reported significant subjective improvement in epiphora at 6-months follow-up. One patient had bilateral granuloma at the surgical site at two weeks and was managed by simple excision and topical tapering steroids. Histopathology revealed hyperplastic epithelium with goblet cells with chronic inflammatory cells in the sub-epithelial region and the stroma. CONCLUSION: The role of the caruncle in the causation of mechanical SALDO needs to be carefully assessed in patients beyond the sixth decade. Excellent objective and subjective outcomes can be achieved by a partial carunculectomy and plica semilunaris excision.

Post-traumatic canalicular fistula: description and review of literature - SALDO update study (SUP) - paper II.

PURPOSE: To discuss the clinical spectrum and management strategies in patients with post-traumatic canalicular fistula (PTCF). METHODS: Retrospective, interventional case series of consecutive patients diagnosed with PTCF over a 6-year study period between June 2016 and June 2022. The demographics, mode of injury, location, and communication of the canalicular fistula were noted. The outcomes of several management modalities including dacryocystorhinostomy, lacrimal gland therapies, and conservative approaches were assessed. RESULTS: Eleven cases with PTCF over the study period were included. The mean age at presentation was 23.5 years (range: 6-71 years), with male: female ratio of 8:3. The median time interval between trauma to presentation at the Dacryology clinic was 3 years (range: 1 week to 12 years). Seven had iatrogenic trauma and four had the canalicular fistula following primary trauma. Management modalities pursued include conservative approach for minimal symptoms, and dacryocystorhinostomy, dacryocystectomy, and lacrimal gland botulinum toxin injection. The mean follow-up period was 30 months (range: 3-months-6 years). CONCLUSION: PTCF is a complex lacrimal condition and the management of the PTCF needs a tailored approach guided by its nature and location and patient symptomatology.

[Dacryocystorhinostomy with a counteropening in the treatment of secondary nasolacrimal duct obstruction after radioiodine therapy]. / Dakriotsistorinostomiya s nalozheniem kontrapertury pri vtorichnoi obliteratsii slezootvodyashchikh putei vsledstvie terapii radioaktivnym iodom.

Among secondary forms of nasolacrimal duct obstruction caused by radioactive iodine therapy, its distal forms localized in the area of the Hasner's valve are predominant. In this regard, during dacryocystorhinostomy (DCR) there is a high probability of developing the sump syndrome, for which the anatomical prerequisite is that the lower edge of the DCR ostium is above the level of obstruction. In such cases, we propose to supplement DCR with a counteropening in the area of the Hasner's valve. PURPOSE: This study analyzes the clinical effectiveness of dacryocystorinostomy with a counteropening. MATERIAL AND METHODS: The outcomes of 49 surgeries (49 patients) with secondary acquired nasolacrimal duct obstruction due to radioactive iodine therapy were analyzed, including 34 DCR and 15 DCR with a counteropening. The clinical outcomes were analyzed over the longest possible period after surgery. The analysis included the severity of tearing on the Munk scale, the characteristic of the formed ostium on the M. Ali scale and the height of the tear meniscus. Differences were considered significant at a confidence level of 95% (p≤0.05). RESULTS: Analysis of the results of the performed surgeries showed that DCR was clinically effective in 30 (88%) cases, DCR with a counteropening - in 15 (100%) cases. The differences were not statistically significant in the total sample, but were statistically significant when comparing the results of surgeries in patients with distal obliteration. CONCLUSION: The developed and clinically tested method of DCR with a counteropening in the area of the Hasner's valve was completely effective in 15 patients with secondary nasolacrimal duct obstruction caused by radioiodine therapy.

[Pharmacological prevention of fibrosis in dacryosurgery]. / Medikamentoznaya profilaktika fibrotizatsii v dakriokhirurgii.

Chronic inflammatory process in the lacrimal drainage system is the main etiological factor leading to dacryostenosis and consequent obliteration - partial and total nasolacrimal duct obstruction. Prevention of this process is an urgent problem in dacryology. Currently, there is very little research on the development and use of conservative methods for treating dacryostenosis using anti-inflammatory, as well as anti-fibrotic drugs. In this regard, the main method of treating lacrimal drainage obstruction is dacryocystorhinostomy. However, the problem of recurrence after this operation has not been resolved. The causes of recurrence can be cicatricial healing of dacryocystorhinostomy ostium, canalicular obstruction, formation of granulations and synechiae in its area. Surgical methods of recurrence prevention are associated with possible complications, and there is conflicting data on the feasibility of their use. Based on this, the development of pharmacological methods for the prevention of fibrosis in dacryology is promising, among which the antitumor antibiotic Mitomycin C is the most studied. However, there are no specific scientifically substantiated recommendations for the use of this drug, and the data on its effectiveness vary. This has prompted researchers to look for and study alternative anti-fibrotic agents, such as antitumor drugs, glucocorticoids, hyaluronic acid, small molecule, biological, immunological and genetically engineered drugs, as well as nanoparticles. This review presents the current data on the efficacy and prospects of the use of these drugs in dacryology.

A case report of chronic dacryocystitis caused by nasal stones.

BACKGROUND: This paper reports a case of chronic dacryocystitis due to nasal stones. CASE PRESENTATION: An 84-year-old male patient was admitted to the hospital with chronic dacryocystitis of the right eye due to tearing and purulent discharge from the right eye for more than 1 month. Antibiotic treatments such as gatifloxacin eye drops were given at other hospitals but did not relieve the symptoms. A computed tomography(CT) scan of the lacrimal duct in our department showed a high-density shadow in the right lacrimal sac area, hypertrophy of the right inferior turbinate, and many nasal calculi in the nasal cavity. The patient was transferred to our otolaryngology department for further treatment, and nasal stones were removed under nasal endoscopy. Three days after surgery, the symptoms affecting the patient's right eye gradually resolved. One month after surgery, the patient underwent a follow-up examination in the ophthalmology clinic; there was no lacrimal purulent discharge from the right eye, and the lacrimal duct could be flushed smoothly. CONCLUSION: Chronic dacryocystitis is often caused by primary nasolacrimal duct obstruction. Cases of chronic dacryocystitis caused by secondary nasolacrimal duct obstruction due to nasal stones are rare in the clinic. This case can serve as a reference for the clinical diagnosis and treatment of chronic dacryocystitis.

Bilateral Congenital Nasolacrimal Duct Obstruction in Williams-Beuren Syndrome.

A 23-year-old patient with Williams-Beuren syndrome presented with ocular irritation and bilateral persistent tearing. Despite probing as an infant which showed bilateral nasolacrimal duct obstruction, dacryocystorhinostomy had been avoided due to the patient's syndromic supravalvular stenosis and related anesthesia risk. As the known diminished production of elastin in Williams-Beuren syndrome causes an array of associated vascular diseases, this case report hypothesizes that the lacrimal duct becomes obstructed through a similar mechanism. This case presents the unique findings of bilateral congenital nasolacrimal duct stenosis in a Williams-Beuren syndrome patient.

A Modified Bicanalicular Crawford Placement Method for Congenital Nasolacrimal Duct Obstruction: Reducing Need for Operative Room Removal.

PURPOSE: This study introduces a method for Crawford bicanalicular stent placement for congenital nasolacrimal duct obstruction by looping the ends to themselves which are tied together with dissolvable sutures to ease in-office removal. METHODS: This is a single institution, retrospective study that evaluates outcomes of patients aged 5 years and under who underwent bicanalicular stenting for congenital nasolacrimal duct obstruction by a single surgeon (G.S.E.) between 2004 and 2020. Only primary surgeries were included in the analysis. Stenting could be accompanied by balloon dilatation and/or turbinate infracture. Age, sex, follow-up time, complications, type of intervention, extrusion, recurrence, and operative room removal were recorded. RESULTS: This study included 56 eyes from 54 patients with a mean age of 19.0 ± 9.5 months (range, 8-50 months). There was a 30.3% extrusion rate, a 5.4% rate of recurrence of disease, and a 3.6% rate of operative room removal. The average follow-up time was 25.1 ± 39.8 months (range, 1-132 months). For patients with or without extrusion, there were no significant differences between age, sex, laterality, type of intervention, follow-up time, or rate of recurrence. Each eye that had recurrence (3 total) or needed operative room removal (2 total) underwent only bicanalicular stenting without accompanying procedures, although the difference in rates between procedures was also not statistically significant. CONCLUSIONS: This method had a low recurrence and operative room removal rate, with similar extrusion and complication rates to other bicanalicular stent and intubation methods for the treatment of congenital nasolacrimal duct obstruction.

Periocular Infection With Nocardia nova Following Dacryocystorhinostomy With Silicone Stent Intubation.

Nocardia species are aerobic, rod-shaped, Gram-positive bacteria that are ubiquitous throughout the environment. Nocardia nova has been reported as the second most prevalent Nocardia species. However, reports of ocular and periocular infection caused by this organism are rare. The authors present a case of a 58-year-old woman with a medical history of acquired nasolacrimal duct obstruction of the left eye who underwent a revision dacryocystorhinostomy with silicone stent intubation and developed a surgical site infection that was culture-positive for N. nova . Treatment consisted of removal of the silicone stent and a prolonged course of oral antibiotics, resulting in the patient's full recovery. This is the second reported case of postoperative periocular N. nova infection after dacryocystorhinostomy and silicone stent intubation.

Outcome of Primary Monocanalicular Stent Placement in Pediatric Down Syndrome Patients with Congenital Nasolacrimal Obstruction.

PURPOSE: Congenital Nasolacrimal duct obstruction (CNLDO) is a relatively common problem in children with Down syndrome (DS). Probing and irrigation (PI) with monocanalicular stent intubation may be less successful than in non-DS patients, thus raising some concerns regarding the preferred treatment in this population. We aimed to analyze the surgical outcome of PI along with monocanalicular stent intubation in children with DS compared with non-DS patients. METHODS: Retrospective cohort study. Thirty-five eyes of 19 children with DS and 1,472 eyes of 1,001 children without DS underwent PI-monocanalicular stent intubation as a primary treatment for CNLDO. All patients were operated on by a single surgeon at the Children's Hospital of Philadelphia between 2009 and 2020. The main outcome measure was a surgical success, defined as the resolution of symptoms after surgery. RESULTS: A total of 1,020 patients were included, 48% females; mean age of 1.9 ± 1.4 years. The mean follow-up time was 35.0 months. The DS patients group consisted of 19 patients. Higher rates of right nasolacrimal duct obstruction and bilateral obstructions were observed in the DS group (100% vs. 73.2%; p = 0.006, and 84.2% vs. 46.8%; p = 0.001, respectively). Patients with DS had a lower success rate (57.1% vs. 92.4%; p < 0 .0001). The median time to failure was 3.1 months in the DS group, and 5.2 months in the group of patients without DS. The hazard ratio comparing DS to the no-DS outcome was 6.6 (95% CI: 3.2-13.7; p < 0.001). CONCLUSIONS: CNLDO in DS is more likely to be bilateral and less likely to resolve after primary monocanalicular stent placement.

Accumulation of 131Iodine in the nasolacrimal sac/duct after radioiodine therapy for papillary thyroid cancer.

SPECT/CT is a powerful tool for assessing unexpected concentrations of radioiodine resulting from benign uptake in organs with sodium-iodide symporter (NIS) expression. We report a case of accumulation of 131Iodine in the nasolacrimal sac/duct after radioiodine therapy for papillary thyroid cancer. A whole-body scan was taken 3 days after the administration of 5.5 GBq of 131Iodine. SPECT/CT images localized the focal tracer uptake in the nasolacrimal sac/duct likely due to nasolacrimal duct obstruction secondary to prior radioiodine or iodine therapies. Hybrid SPECT/CT allows precise anatomical localization and help differentiate benign mimics of disease, which can alter patient management.

Soft stop on syringing and probing may have a high false-positive rate in diagnosing pre-sac obstruction.

PURPOSE: To determine the diagnostic value of 'soft stops' encountered during lacrimal syringing and probing. METHODS: Single-center retrospective review. Adult patients with epiphora attending a tertiary lacrimal clinic from May 2010 to April 2021 were reviewed. Cases with evidence of soft stop encountered during lacrimal syringing/probing were included, and patients with possible canaliculitis or a history of lacrimal surgery were excluded. Findings of syringing/probing consistent with pre-sac obstruction were correlated with dacryocystography (DCG) and surgical findings. RESULTS: 53 (10.2%) canalicular systems had soft stops on syringing/probing and were included in the analysis. The mean age of the patients was 63.8 ± 15.6 (range 28-87) years, and 27 (65.9%) were females. Intraoperative examination findings were available for 27 of 30 cases that underwent lacrimal surgery and DCG was available for 40 systems. Pre-sac obstruction found on syringing/probing was confirmed in 40% and 37% of cases on DCG and surgery, respectively. The correlation between syringing/probing and DCG was stronger for canalicular than for common canalicular location (p = 0.016). Canalicular stenosis on syringing/probing manifested as pre-sac abnormality on DCG in 5/7 (71.4%) compared to 0/6 common canalicular stenosis cases (p = 0.021). Based on the surgical findings, the false-positive rate of a soft stop on syringing/probing was highest for common canalicular 'stenosis' (100%) and lowest for canalicular 'block' (45.5%; p = 0.093). Findings of pre-sac obstructions on DCG were confirmed in 85.7% of the cases intraoperatively (p = 0.035 compared to syringing/probing alone). CONCLUSIONS: Soft stops on probing showed poor correlation with DCG and surgical findings, particularly in common canalicular location.

A simple and efficient technique for suturing and knotting during endoscopic dacryocystorhinostomy.

PURPOSE: This study evaluated the long-term outcomes of endoscopic suturing and knotting-dacryocystorhinostomy (eSK-DCR) without the use of a stent or mitomycin C. METHODS: A prospective interventional case series was performed on patients with nasolacrimal duct obstruction (NLDO) who underwent eSK-DCR at Zhongshan Ophthalmic Center from October 2019 to December 2019. The surgeon sutured the lacrimal sac mucosa with the nasal mucosa by tying knots under endoscopic DCR. Subject demographics, preoperative data and postoperative data were collected, including clinical presentation, Munk score for epiphora, surgical indications, operation time, duration of knotting, number of knots, endoscopic ostium size, complications, and anatomical and functional success. Anatomic success was defined as patent ostium on lacrimal irrigation, and functional success was defined as subjective improvement in symptoms. Statistical analysis was performed by IBM SPSS software (Version 20.0; SPSS Inc., Chicago, IL, USA). RESULTS: A total of 60 patients (71 eyes) underwent pure eSK-DCR. Of these, 95.0% (57/60) were females. The mean age of the patients was 54.7 years. The mean surgical time was 37.60 min, and the average time for each knotting was 2.86 min. Endoscopic evidence found that all patients showed patent ostium and normal healing of the flaps after 4 weeks. The Munk scores dropped significantly at 6 months postoperatively compared to preoperative scores (P < 0.0001). Although 4 patients (7 eyes) were lost to follow-up at the end of the 2-year period, the anatomical and functional success remained stable during the 2-year follow-up period (anatomical, 100%; functional, 87.5%). No serious complications were detected during the follow-up period. CONCLUSION: Pure eSK-DCR is a simple and reliable therapeutic method for the management of NLDO. The surgical outcomes were good and remained stable beyond 6 months postoperatively.

Importance of etiology in canalicular obstruction surgery.

PURPOSE: The treatment options for canalicular obstruction remain controversial, and there are different approaches. In this study, we aimed to evaluate the success of balloon dilatation and silicon tube intubation according to the etiology in patients with canalicular obstruction. METHODS: The files of 91 patients with isolated monocanalicular obstruction were retrospectively reviewed. Patients were grouped according to surgical methods (Group A: both balloon dilatation and silicon tube intubation; Group B: Only balloon dilatation) and etiologies (topical anti-glaucomatous usage-related, inflammatory, chemotherapy-related, radiotherapy-related, trauma-related, idiopathic). Preoperative and postoperative Munk scores and lacrimal irrigation results were noted in all cases. RESULTS: Munk score was found to be statistically significantly lower in the 1st year in both groups. The patency rate with lacrimal syringing was found to be statistically significantly higher in group A. Success rates both in the munk score and lacrimal passage patency were found to be statistically significantly lower in inflammatory etiology than other etiologies. CONCLUSIONS: Both techniques can be used as first-line therapies for canalicular obstruction. It should be considered that recurrence may develop in stenosis of inflammatory origin and more invasive surgery may be required.

Topographic and anatomical features of the nasolacrimal duct obstruction due to radioiodine treatment.

PURPOSE: To investigate the topographic and anatomical features of secondary acquired nasolacrimal duct obstruction (SALDO) due to radioiodine therapy. METHODS: Dacryocystography-computed tomography (DCG-CT) scans of the nasolacrimal ducts in 64 cases with SALDO due to radioiodine therapy and in 69 cases with primary acquired nasolacrimal duct obstruction (PANDO) were studied. The anatomical site of obstruction was located, and morphometric characteristics of the nasolacrimal ducts were calculated: volume, length, and average sectional area. The statistical analysis was performed using the t-criterion, ROC analysis, and the odds ratio (OR). RESULTS: The mean nasolacrimal section area was 10.7 ± 0.8 mm2 in patients with PANDO and 13.2 ± 0.9 mm2 in patients with SALDO due to radioiodine therapy (p = 0.039); the AUC value in ROC analysis for this parameter was 0.607 (p = 0.037). The development of "proximal" obstruction including lacrimal canaliculi obstruction and obstruction at the site of the lacrimal sac was 4.076 times more likely (CI: 1.967-8.443) in patients with PANDO than in patients with SALDO due to radioactive iodine exposure. CONCLUSIONS: By comparing CT scans of the nasolacrimal ducts, we observed that in SALDO obstruction due to radioactive iodine therapy is predominantly "distal," while in PANDO it is more often "proximal." The development of obstruction within SALDO is followed by more pronounced suprastenotic ectasia.