The Communication between Ocular Surface and Nasal Epithelia in 3D Cell Culture Technology for Translational Research: A Narrative Review.

There is a lack of knowledge regarding the connection between the ocular and nasal epithelia. This narrative review focuses on conjunctival, corneal, ultrastructural corneal stroma, and nasal epithelia as well as an introduction into their interconnections. We describe in detail the morphology and physiology of the ocular surface, the nasolacrimal ducts, and the nasal cavity. This knowledge provides a basis for functional studies and the development of relevant cell culture models that can be used to investigate the pathogenesis of diseases related to these complex structures. Moreover, we also provide a state-of-the-art overview regarding the development of 3D culture models, which allow for addressing research questions in models resembling the in vivo situation. In particular, we give an overview of the current developments of corneal 3D and organoid models, as well as 3D cell culture models of epithelia with goblet cells (conjunctiva and nasal cavity). The benefits and shortcomings of these cell culture models are discussed. As examples for pathogens related to ocular and nasal epithelia, we discuss infections caused by adenovirus and measles virus. In addition to pathogens, also external triggers such as allergens can cause rhinoconjunctivitis. These diseases exemplify the interconnections between the ocular surface and nasal epithelia in a molecular and clinical context. With a final translational section on optical coherence tomography (OCT), we provide an overview about the applicability of this technique in basic research and clinical ophthalmology. The techniques presented herein will be instrumental in further elucidating the functional interrelations and crosstalk between ocular and nasal epithelia.

Aqueous tear assessment in dogs: Impact of cephalic conformation, inter-test correlations, and test-retest repeatability.

OBJECTIVE: To characterize diagnostic findings, test-retest repeatability, and correlations among lacrimal tests in dogs of diverse cephalic conformations. ANIMAL STUDIED: Fifty healthy dogs (25 brachycephalic, 25 nonbrachycephalic). PROCEDURES: A series of diagnostics were performed in each dog, allowing for a 10-minute interval between tests and repeating each test 24 hours later under similar conditions: corneal tactile sensation (CTS), strip meniscometry test (SMT), phenol red thread test (PRTT), endodontic absorbent paper point tear test (EAPPTT), Schirmer tear test-1 without (STT-1) or with nasolacrimal stimulation (NL-STT1), and Schirmer tear test-2 (STT-2). RESULTS: Mean ± SD test values were lower in brachycephalic vs. nonbrachycephalic dogs (except for SMT; 7.4 ± 2.0 mm/5 seconds vs 7.3 ± 2.4 mm/5 seconds), with statistically significant differences noted for CTS (1.8 ± 0.5 cm vs 3.4 ± 0.8 cm), PRTT (37.2 ± 4.0 mm/15 seconds vs 41.1 ± 5.5 mm/15 seconds), STT-1 (20.1 ± 3.4 mm/min vs 23.3 ± 5.7 mm/min), STT-2 (13.0 ± 3.4 mm/min vs 16.9 ± 3.9 mm/min), and NL-STT1 (23.2 ± 3.6 mm/min vs 27.1 ± 5.4 mm/min), and nonsignificant differences for EAPPTT (16.6 ± 2.7 mm/15 seconds vs 17.5 ± 2.9 mm/15 seconds). Nasolacrimal stimulation increased STT-1 values by 18% on average. Correlations among tests were generally weak to moderate (r < .70) except for a strong correlation between STT-1 and NL-STT1 (r = .83, P < .001). Test reliability was good although test-retest repeatability was generally poor to moderate, as depicted by low intraclass correlation coefficients (ICC ≤ 0.75) and wide 95% limits of agreement, except for CTS (ICC = 0.91). CONCLUSIONS: Corneal sensitivity and aqueous tear secretion are lower in brachycephalic dogs. A comprehensive assessment of the ocular surface requires the combination of several diagnostic tests. The nasolacrimal reflex may provide a useful diagnostic and therapeutic tool in dogs.

Lacrimal drainage function after cheese wiring of lacrimal passage intubation.

PURPOSE: To investigate how cheese wiring affects lacrimal drainage function by quantitative assessment of tear function and punctal dimensions. METHODS: Patients who underwent lacrimal passage intubation between January 2017 and September 2018 were enrolled prospectively. Among these patients, those with postoperative cheese wiring who received lacrimal passage intubation in one eye met the criteria for further investigation. The subjective symptoms of epiphora, dimensions of puncta, lower tear meniscus, and tear clearance were assessed postoperatively in both the involved eye and untreated contralateral eye. Punctum dimensions were analysed using the digital slit-lamp image. Tear meniscus and tear clearance were assessed by anterior segment optical coherence tomography. RESULTS: Postoperative cheese wiring was observed in 68 of 314 eyes. Among these cases, 36 patients (age 70.5 ± 11.7 years) had cheese wiring only in one eye: with the involvement of both puncta in 15 patients (group A) and only the lower punctum in 21 patients (group B). There was no patient with the involvement of only the upper punctum. While tear function of the involved eyes in group B did not differ from that of the untreated eye, it was significantly decreased in group A compared with that in untreated control eyes (p < 0.05). The tear clearance rate correlated significantly with the upper punctum dimensions (p < 0.05), but not with the lower punctum. CONCLUSION: Analysis of cheese wiring after lacrimal passage intubation with tear function demonstrated that the integrity of the puncta and the canaliculus is important for lacrimal drainage.

New technique to reduce systemic side effects of timolol eye drops: The tissue press method-Cross-over clinical trial.

IMPORTANCE: Nasolacrimal occlusion (NLO) is effective in reducing systemic absorption of eye drop medication but it is difficult and often performed poorly. We propose an alternative easier and equally effective technique. BACKGROUND: To test the effectiveness of systemic absorption, we evaluated plasma concentration and ocular effects after topically administered timolol and compared to NLO. DESIGN: Cross-over trial carried out in Capital Eye Specialist, Wellington. PARTICIPANTS: A total of 21 subjects over 18 years without contraindications for topical beta-blocker medication and not using systemic beta-blockers. METHODS: During three clinic visits separated by at least one week, alternative approaches to reduce systemic eye drop absorption were tested. These were: (a) nasolacrimal (punctal) occlusion for 5 min, (b) tissue press method or (c) no intervention. Timolol plasma levels were measured 1 h after drop application. At each visit, baseline measurement of blood pressure, heart rate and intraocular pressure (IOP) were performed, and repeated 1 h after timolol 0.5% eye drop application. MAIN OUTCOME MEASURES: Comparison of timolol plasma concentration after each intervention. Secondary outcome measurements included effects on blood pressure, heart rate and IOP. RESULTS: Plasma timolol concentrations after tissue press method and NLO were significantly lower than those without intervention. Comparing tissue press method to NLO, there were no significant differences in plasma levels of timolol, blood pressure, heart rate or IOP. CONCLUSION AND RELEVANCE: The tissue press method is equally effective as NLO in reducing systemic absorption of timolol. It is also easier and faster to administer.

Lacrimal drainage anatomy in the Japanese population.

PURPOSE: The aim of this study is to provide a comprehensive and clinically relevant review of the lacrimal drainage anatomy in the Japanese population. METHODS: A thorough search on the lacrimal drainage anatomy in the Japanese population was performed using PubMed and Ichushi Web, which is managed by the Japan Medical Abstracts Society, for related studies up to December 2018. Published books on the same topic were also reviewed. Data from all articles and book chapters were reviewed, analyzed, and incorporated in this review. RESULTS: This review presents the subparts of the lacrimal drainage anatomy in a chronological manner, from proximal to distal. The location, dimensions, position or angle, histology (with some reference to the essential clinical functions and physiology of the lacrimal drainage system) are described in this review. CONCLUSIONS: Understanding lacrimal drainage anatomy in the Japanese population is essential to provide insight as to how it is important to consider patients as individuals, with unique and specific anatomies, and uphold a patient-specific approach.

Continuous Positive Airway Pressure Thresholds for Nasolacrimal Air Regurgitation in a Cadaveric Model.

PURPOSE: To elucidate the mechanisms underlying nasolacrimal air regurgitation (AR) in the setting of continuous positive airway pressure therapy. METHODS: Twelve nasolacrimal systems of 6 fresh female human cadavers were evaluated individually for AR using continuous positive airway pressure therapy before any nasolacrimal procedure. Cadavers were then randomly assigned to undergo nasolacrimal duct probing or endoscopic dacryocystorhinostomy and then each hemisystem was again evaluated for AR. The pressure where AR was first observed (discovery pressure) or maximum possible pressure in systems without AR was recorded. In systems that demonstrated AR, the pressure was then gradually decreased to the lowest pressure where regurgitation persisted. This pressure was recorded as the secondary threshold pressure. RESULTS: None of the 12 unoperated nasolacrimal systems or the 6 systems that underwent nasolacrimal duct probing demonstrated AR through the maximum continuous positive airway pressure therapy (30 cm H2O). After endoscopic dacryocystorhinostomy, all 6 nasolacrimal systems demonstrated AR. The mean discovery pressure was 16.0 cm H2O (range, 14.0-18.0 cm H2O) and mean secondary threshold pressure was 7.25 cm H2O (range, 6.5-8.0 cm H2O). CONCLUSIONS: Air regurgitation during continuous positive airway pressure therapy in the setting of prior endoscopic dacryocystorhinostomy can be replicated in a cadaver model. The secondary threshold pressures required for AR in this model were similar to AR pressures reported clinically. Prior to dacryocystorhinostomy, patients using continuous positive airway pressure therapy should be counseled on AR, and physicians should consider this phenomenon when evaluating ophthalmic complaints in postoperative patients on positive airway pressure therapy.

[Anatomy and physiology of the nasolacrimal ducts]. / Anatomie und Physiologie der ableitenden Tränenwege.

Ophthalmologists and interventional radiologists are not the only professionals for whom diseases of the efferent tear duct system occupy centre stage; this applies also to ENT specialists involving endonasal conservative or surgical treatment. On the basis of current knowledge and taking account of results yielded by own research in recent years and of clinical aspects, we here give an overview of basic knowledge on the anatomy and physiology of the nasolacrimal system. In doing so functional aspects regarding tear transport as well as embryological and pathophysiological issues are integrated.

Movement of the lacrimal canalicular wall under intracanalicular pressure changes observed with dacryoendoscopy.

BACKGROUND: Movement of the lacrimal canalicular wall has been speculated to occur during blinking. Movement of the common internal ostium has been observed under nasal endoscopy, and pressure changes in the lacrimal canalicular cavity have been observed with a pressure sensor; however, lacrimal canalicular wall movement under pressure changes has not been observed. PURPOSE: To examine movement of the lacrimal canalicular wall under intracanalicular pressure changes using dacryoendoscopy. METHODS: The authors examined 20 obstruction-free lacrimal canaliculi in 10 patients. A dacryoendoscope was inserted, and water was poured into the intracanalicular cavity via the dacryoendoscope's water channel. The water was then poured or suctioned to cause positive or negative pressure changes in the intracanalicular cavity, and movement of the lacrimal canalicular wall was examined. RESULTS: The lacrimal canalicular wall moved flexibly with pressure changes. Under positive pressure, the intracanalicular cavity was dilated; however, it narrowed under negative pressure. The extent of movement was more dramatic in the common canalicular portion than the proximal canalicular portion. CONCLUSIONS: Intracanalicular pressure changes cause movement of the lacrimal canalicular wall. There was a consistent relationship between intracanalicular cavity changes and pressure changes, possibly contributing to lacrimal drainage of the canaliculus.

Lacrimal sac movement under intrasac pressure changes observed with dacryoendoscopy.

PURPOSE: To examine movement of the intrasac cavity under intrasac pressure changes with dacryoendoscopy. METHODS: The authors examined 10 lacrimal sacs (3 right and 7 left) without lacrimal tract obstruction in 10 Japanese patients (3 men and 7 women) aged 35 to 86 years (average, 62.8 years). These were the contralateral sides of the sides with nasolacrimal duct obstruction that were treated with dacryocystorhinostomy. After enlarging a superior lacrimal punctum, a dacryoendoscope (FT-203F; FiberTech) was inserted. When the tip of the dacryoendoscope passed through the common internal ostium, the handgrip was rotated 90° superiorly to face the tip inferiorly. Water was poured into the cavity throughout this process via the water channel of the dacryoendoscope. Then, with the water poured or suctioned from the same channel, namely causing positive or negative pressure changes in the intrasac cavity, movement of the lacrimal sac wall was examined with dacryoendoscopy. RESULTS: The lateral wall of the lacrimal sac moved with pressure changes fairly flexibly. Under positive pressure, the wall moved outward, but it moved inward under negative pressure. CONCLUSIONS: The present study demonstrated movement of the lacrimal sac wall with intrasac pressure changes, which was suggestive of its contribution to lacrimal drainage of the sac.

Diagnostic imaging of the nasolacrimal drainage system. Part I. Radiological anatomy of lacrimal pathways. Physiology of tear secretion and tear outflow.

Excessive watering of the eye is a common condition in ophthalmological practice. It may be the result of excessive production of tear fluid or obstruction and insufficiency of efferent tear pathways. The differentiation between obstruction and insufficiency of the lacrimal pathways is still clinically questionable. In the diagnostic process it is necessary to perform clinical tests and additional diagnostic imaging is often needed. Dacryocystography, with or without the extension of the dynamic phase or subtraction option, still remains the criterion standard for diagnostic imaging of the lacrimal obstruction. It may help to clarify the cause and exact place of the obstruction and provide information for further management, especially surgical treatment. Increasingly, new techniques are used in diagnostic imaging of the lacrimal tract, such as computed tomography, magnetic resonance, and isotopic methods. Adequate knowledge of the anatomy and physiology of the lacrimal system and the secretion and outflow of tears is the basis for proper diagnostic imaging. The purpose of this paper is to present the exact anatomy of the lacrimal system, with particular emphasis on the radiological anatomy and the current state of knowledge about the physiology of tear secretion and drainage.

Retrograde air escape via the nasolacrimal system: a previously unrecognized complication of continuous positive airway pressure in the management of obstructive sleep apnea.

BACKGROUND: Continuous positive airway pressure (CPAP) is the gold standard treatment for moderate to severe obstructive sleep apnoea (OSA). Eye-related side effects of CPAP are commonly attributed to a poorly sealed mask, allowing leaked air to blow over the eye. CASES: We present 3 cases where attended polysomnography (A-PSG) demonstrated CPAP-associated retrograde air escape via the nasolacrimal system (CRANS) in the absence of any mask leaks. Symptoms included dry eye, epiphora, air escape from the medial canthus, and eyelid flutter. Symptoms were controlled with a variety of surgical and nonsurgical techniques. CONCLUSIONS: CRANS represents a previously undescribed clinical entity. CRANS may be responsible for some CPAP-related eye side effects and possibly for rarer secondary eye complications, including conjunctivitis and corneal ulceration. CRANS should be suspected in any patient on CPAP complaining of eye symptoms. CRANS may be diagnosed through careful observation during A-PSG and confirmed by performing a "saline bubble test." Management options include nonsurgical (mask alternatives, humidification, nasopharyngeal airway) and surgical techniques (nasal airway surgery, inferior turbinate out-fracture and adhesion, injection of bulking agent around Hasner's valve).

The nasolacrimal duct of anuran amphibians: suggestions on its functional role in vomeronasal perception.

Tear secretions discharged by the Harderian gland are suggested to function as a solvent for molecules sensed by the vomeronasal organ (VNO) in anurans. It has been assumed that chemical stimuli are absorbed at the surface of the eye to be carried - together with the lacrimal fluid - into the nasal cavity via the nasolacrimal duct. In the study presented herein, we examined the intranasal anatomy of 10 different anuran species to analyse the opening region of the nasolacrimal duct and its functional relationship with the VNO and the external naris. In addition, vital staining of the nasal cavities was conducted. Our results indicate that stimuli reaching the VNO are more likely to be ingested through the nostril than via the eye. In many cases the intranasal orifice of the nasolacrimal duct shows a close proximity to the external naris and simultaneously we observed a noticeable distance to the VNO. We suggest that the secretions of the Harderian gland are carried to the external naris by the nasolacrimal duct, where they bind chemical stimuli that are subsequently actively transported into the VNO. In some of the investigated species the opening region of the tear duct was situated in a more caudal part of the nasal cavity and closer to the VNO. In these cases a conspicuous system of channels can be found, which is suspected to carry the intruding medium of smell from the nostril to the nasolacrimal aperture.

Nasal-associated lymphoid tissue is not an absolute requirement for the induction of rat tear IgA antibody responses.

UNLABELLED: PURPOSE/AIM OF STUDY: The purpose of this work was to determine whether rat nasal-associated lymphoid tissue is required for the induction of tear IgA responses. MATERIALS AND METHODS: Particulate antigen in the form of DNP-BSA encapsulated in cationic microparticles was applied topically to the eyes (ocular topically) of rats that had the nasolacrimal ducts temporarily plugged with chromic gut suture material. Eye washes and serum were monitored for development of antigen specific IgA and IgG, respectively. To track the particulate uptake, fluorescent latex beads were applied topically to the eyes of plugged and unplugged animals. The nasal-associated lymphoid tissue and the draining lymph nodes were then examined for the presence of the fluorescent beads. RESULTS: It was found that the chromic gut suture was effective in blocking the passage of antigen into the nasopharyngeal cavity for at least 24 hr. Tear antigen-specific IgA levels found in the eyes of plugged animals were not significantly lower from those of unplugged animals. Serum IgG antibody levels were also similar between the two groups. In animals with plugged nasolacrimal ducts, fluorescent beads were found predominately in the superficial cervical lymph nodes, which have been shown to drain the surface of the eye. CONCLUSIONS: These results indicate that particulate antigen can be taken up by the conjunctiva and transported to the draining lymph nodes, showing that antigen does not need to access nasal-associated lymphoid tissue to induce tear IgA antibody responses.

Endoscopic dacryocystorhinostomy for acquired nasolacrimal duct obstruction.

OBJECTIVE: To evaluate the results of endoscopic dacryocystorhinostomy performed to treat acquired nasolacrimal duct obstruction. DESIGN: Retrospective analysis of the outcome of endoscopic dacryocystorhinostomy performed in the conventional manner (i.e. without power instruments or laser) to treat acquired nasolacrimal duct obstruction. SUBJECTS: Outcomes for 300 patients with acquired nasolacrimal duct obstruction were evaluated. Cases with congenital or traumatic blockages were excluded. All the cases were evaluated for nasolacrimal duct blockage by the syringing and regurgitation test. Surgery was performed under local anaesthesia with sedation. Follow up was conducted by syringing and nasal endoscopy, up to one year. Results were compared with published data for endoscopic and external dacryocystorhinostomy. RESULTS: Outcomes were evaluated subjectively using patient symptoms, syringing results and endoscopic appearance. All cases were symptom-free following endoscopic dacryocystorhinostomy. Revision surgery was performed in 18 cases. Stents were placed in 10 patients, of which two developed granulations. Septoplasty was performed in 25 cases to gain access to the lacrimal sac area. CONCLUSION: The results were comparable with published data for endoscopic and external dacryocystorhinostomy.

The importance of eyelid closure and nasolacrimal occlusion following the ocular instillation of topical glaucoma medications, and the need for the universal inclusion of one of these techniques in all patient treatments and clinical studies.

PURPOSE: To review the effects of nasolacrimal occlusion (NLO) and eyelid closure (ELC) on the ocular and systemic absorption of topically applied glaucoma medications and emphasize the need for the universal application of these techniques during patient treatment and in clinical studies of topically applied glaucoma medications. METHODS: Following a review of data suggesting great clinical benefit from NLO and ELC, the absence of inclusion of these simple techniques in published studies of topical glaucoma medications is identified. The effect of this oversight on these studies is noted with reference to each of the 5 major groups of glaucoma medications. RESULTS: A review of the literature suggests that NLO and ELC improve intraocular penetration of topically applied glaucoma medications and discourage systemic absorption. The US Food and Drug Administration and the National Institutes of Health discourage the inclusion of these techniques in studies of the efficacy and toxicity of topically applied glaucoma medications. Consequently, all glaucoma studies reported in the literature lack the inclusion of these techniques for 5 minutes. This omission has major implications for patient informed consent, study protocol consistency, and the value of clinical studies, and directly affects the therapeutic index of glaucoma medications in unpredictable and undesirable ways. The undesirable influence on the therapeutic index of each drug influences the safety and efficacy and has implications for the cost of medical treatments, the reproducibility of clinical study results, and dosing regimens, including those of combination therapy, as reflected in the peer-reviewed literature. CONCLUSIONS: Patients should use NLO or ELC for 5 minutes following eye drop treatment with topically applied glaucoma medications. Furthermore, it is essential that these techniques be included in all clinical studies of topically applied glaucoma medications to ensure the most favorable therapeutic index and its accurate determination. This will also help provide the most consistent, reliable, and reproducible study results.

The effect of lateral osteotomy of septorhinoplasty on nasolacrimal duct functions: a radionuclide imaging study.

BACKGROUND: The aim of this study was to evaluate the effects of lateral osteotomy of septorhinoplasty on nasolacrimal duct functions by dacryoscintigraphy. METHODS: The study group comprised 60 nasolacrimal systems of 30 consecutive patients who underwent septorhinoplasty. Dacryoscintigraphy images were taken in the preoperative period and postoperative 1st week and 3rd month. After Tc-99m pertechnetate instillation, dynamic images were obtained every 15 seconds. For cases of normal drainage, the study was terminated after 10 minutes but when obstruction was suspected, external ocular massage and rapid nasal inspiration were applied and the test was extended for an additional 10 minutes. Systems were classified either as passage without massage (normal nasolacrimal test), passage with massage (physiological obstruction), or presac or postsac obstruction (partial or complete obstruction) according to test results. Transit time was determined for cases with normal test or physiological obstruction. RESULTS: In the preoperative period eight systems (two presac and six postsac) had obstruction. There were a total of 11 (18.3%) additional systems with obstruction (4 presac and 7 postsac) in the 1st postoperative week and patient symptoms were not in complete agreement with the test results in this period. By the 3rd month, nine systems (three presac and six post sac) had obstruction. Transit time was prolonged in both the postoperative 1st week and the postoperative 3rd month tests compared with the preoperative tests (p = 0.000 and p = 0.023, respectively). CONCLUSION: We did not encounter any permanent obstructions after lateral osteotomy of rhinoplasty. Temporary obstructions in the 1st postoperative week improved to normal preoperative status by the postoperative 3rd month.

The human nasolacrimal ducts.

The human nasolacrimal ducts are a borderland of the disciplines ophthalmology and otorhinolaryngology, which work close together in the treatment of nasolacrimal disorders. However, little knowledge exists concerning the physiology of the nasolacrimal system and, therefore, its pathophysiology. The aim of the present investigations was to obtain a better understanding of tear flow physiology, microbial defence strategies and pathophysiological processes by analysing the nasolacrimal system, thus opening new perspectives against existing therapeutical concepts of diseases of the nasolacrimal ducts. The human nasolacrimal ducts consist of the upper and the lower lacrimal canaliculus, the lacrimal sac and the nasolacrimal duct. They drain the tear fluid from the ocular surface into the lower meatus of the nose. The lining epithelium of the lacrimal sac and the nasolacrimal duct is faced by microvilli, and animal experiments in rabbits support the hypothesis that tear fluid components are absorbed in the human nasolacrimal system. Evidence of seromucous glands, intraepithelial lipids and a specific mucus layer leads to the conclusion that the normal three-layering of the tear film is also present in the nasolacrimal ducts. Based on its composition, the mucus layer, which is mainly synthesised by goblet cells and intraepithelial mucus glands, functionally serves as a simplified drainage of tear fluid, and it is attributed similar properties to epithelia of the gastrointestinal tract. Further defence mechanisms are represented by antimicrobial peptides IgA and immunocompetent cells (lymphocytes and macrophages) which show intraepithelially and subepithelially a special distribution. Moreover, organised lymphoid tissue is present, which reveals the cytomorphologic and immunophenotypic characteristics of mucosa-associated lymphoid tissue. The wall of the lacrimal sac and the nasolacrimal duct are made up of a helical system of different connective tissue fibres. Wide luminal vascular plexus are embedded in this helical system, which is comparable to a cavernous body. Caudally, the vascular system is connected to the cavernous body of the inferior turbinate. With distension the system may be "wrung out" due to its medial attachment and helically arranged fibrillar structures. Thereby, tear fluid is drained distally. The embedded blood vessels underlie vegetative control. By means of this innervation, the specialised blood vessels permit regulation of blood flow by opening and closing the lumen of the lacrimal passage as effected by the engorgement and subsidence of the cavernous body, at the same time regulating tear outflow. Related functions, such as a role in the occurrence of epiphora related to emotional responses, are relevant. Moreover, malfunctions in the cavernous body and in its innervation may lead to disturbances in the tear outflow cycle, ocular congestion or total occlusion of the lacrimal passage. Thus, the pathophysiology of primary acquired dacryostenosis can be explained: Descending inflammation from the eye or ascending inflammation from the nose initiates swelling of the mucous membrane, remodelling of the helical arrangement of connective tissue fibres, malfunctions in the subepithelial cavernous body with reactive hyperaemia, and temporary occlusion of the lacrimal passage. In the follow-up, repeated isolated occurrence of dacryocystitis leads to structural epithelial and sub-epithelial changes, which may lead either to a total fibrous closure of the lumen of the efferent tear duct or to a non-functional segment in the lacrimal passage that is manifest on syringing. The normally constant absorption of tear fluid components into the blood vessels of the surrounding cavernous body that are connected to the blood vessels of the outer eye could be a feedback signal for tear fluid production, which comes to a halt if these tear components are not absorbed. Thus, dry eye could be initiated. Defective stimulation of tear duct-associated lymphoid tissue (TALT) could result in abnormal immune deviation at the ocular surface leading to an autoimmunologic response that could cause dry eye pathology.