Tear Outflow Research Articles

Das okuläre Surfactant-System und dessen Rolle bei entzündlichen Erkrankungen der Augenoberfläche

The amphiphilic surfactant proteins B (SP-B) and C (SP-C) are tightly bound to phospholipids. These proteins play important roles in maintaining the surface tension-lowering properties of pulmonary surfactant. Surfactant protein A (SP-A) and D (SP-D) are hydrophilic and are thought to have a role in recycling surfactant and, especially, in improving host defense in the lung. Moreover, SP-A supports the hydrophobic surfactant proteins B and during surfactant subtype assembly and inhibits the secretion of lamellar bodies into the alveolar space. During recent years surfactant proteins have also been detected at locations outside the lung such as the lacrimal apparatus. In this review, the latest information regarding SP function and regulation in the human lacrimal system, the tear film and the ocular surface is summarised with regard to dry eye, rheological and antimicrobial properties of the tear film, tear outflow, certain disease states and possible therapeutic perspectives.

Anatomischer und subjektiver Erfolg einer strukturierten chirurgischen Therapiestrategie zum Management der chronischen Epiphora – eine postoperative Zufriedenheitsanalyse

Epiphora is the result of hypersecretion or reduced tear outflow because of relative or absolute obstruction of the lacrimal system. For the treatment a specific surgical procedure is usually required. Herein we present the subjective and objective findings of 243 consecutive patients with non-irritative induced epiphora, who underwent an operation in a standardised therapy scheme, which is used at the eye departments of the Universities of Lübeck and Würzburg. In a retrospective cohort study 243 patients were included who underwent lateral tarsal strip (n = 72), external dacryocystorhinostomy (DCR) in the case of an absolute nasolacrimal duct obstruction (NLDO) (n = 116) and relative NLDO (n = 25), DCR with canalicular surgery (n = 18) and simple canalicular surgery (n = 12) with a follow-up of at least 6 month. Common patient and cosmetical satisfaction, intensity of symptoms and further symptoms of 168 patients were evaluated by sending a questionnaire with subsequent telephone survey. Objective findings were recorded from hospital charts. 59.5% of the patients were free of complaints, 19.6% had an absolute decrease of symptoms (epiphora outside and in windy weather) and 20.8 % persistent epiphora (symptoms both in- and outside persisted). 81% of patients with absolute NLDO and 57% with relative NLDO were graded as being free of symptoms, 7% (24%) as a relative decrease and 12% (19%) as a persistence of symptoms. There was a significant difference in success between these indications (p = 0.018). Patency of the lacrimal system assessed by irrigation was found in 95% (absolute NLDO). Commonly, 73.8% were satisfied, 7.7% indifferent and 18.4 % not satisfied. 4 patients were cosmetically not satisfied. Use of a standardised therapy scheme reduces the symptoms in 79.1% of the patients. In patients with absolute NLDO external DCR achieves an anatomic success rate of 95% and a subjective improvement in 88% with excellent cosmetic results. In comparison with absolute NLDO the success rate of relative NLDO is lower, but still with a subjective improvement in 81%. Our results show that postoperative success depends on the preoperative cause of the epiphora.

Buccal Mucous Membrane Graft-Assisted Lacrimal Drainage Surgery

Dacryocystorhinostomy (DCR) success may depend on mucous membrane alignment across the osteotomy and entire surgical lacrimal outflow conduit. Scar tissue, obliteration of the lacrimal sac, and obstruction at the level of the common canaliculus may result from prior surgery or may occur as an isolated problem. We describe and evaluate the efficacy of a technique of grafting autologous buccal mucous membrane during external DCR in cases complicated by scarring and/or common canalicular obstruction. We retrospectively reviewed 11 nasolacrimal outflow system obstructions (in 9 patients) treated with a buccal mucous membrane graft-assisted DCR. The surgical technique is described in detail. All cases presented with insufficient nasolacrimal outflow. Ten tear ducts failed prior DCR procedures, while one case had isolated common canalicular obstruction, resistant to multiple probing and intubation and was previously recommended a Jones tube procedure. Three tear outflow systems (in 2 patients) exhibited common canalicular obstruction; the rest were obstructed at the level of the lacrimal sac. Two patients had bilateral obstruction. Ten eyes had symptomatic epiphora. One eye had dacryocystitis alone, and 2 eyes had dacryocystitis and epiphora. Six tear ducts had more than one previous DCR procedure. Four tear ducts had prior endonasal DCR procedures, while 6 had a previous external DCR. All eyes with epiphora preoperatively had complete relief of tearing. All cases of dacryocystitis resolved with no recurrences. Nine tear ducts were patent to irrigation testing postoperatively (2 were not tested). Buccal mucous membrane grafting may improve the success of DCR in cases complicated by scarring, mucosal shortage, and/or common canalicular obstruction.

Tear Film and Ocular Surface Surfactants

The hydrophobic surfactant proteins B (SP-B) and C (SP-C) are tightly bound to phospholipids. These proteins play important roles in maintaining the surface tension-lowering properties of pulmonary surfactant. Surfactant protein A (SP-A) and D (SP-D) are extremely hydrophilic and are thought to have a role in recycling surfactant and especially in improving host defense in the lung. Moreover, SP-A supports the hydrophobic surfactant proteins during surfactant sub- type assembly and inhibits secretion of lamellar bodies into the alveolar space. During recent years surfactant proteins have also been detected at locations outside the lung such as the lacrimal apparatus. In this review, the latest information regarding SP function and regulation in the human lacrimal system, the tear film and the ocular surface is summarized with regard to mucous epithelial integrity, rheological and antimicrobial properties of the tear film, tear outflow, certain disease states and possible therapeutic perspectives.

Anatomie und Physiologie der ableitenden Tränenwege

The human nasolacrimal ducts consist of the upper and lower lacrimal canaliculi, the lacrimal sac and the nasolacrimal duct and drain tear fluid from the ocular surface into the nose. The lining epithelium of the lacrimal sac and the nasolacrimal duct is lined by microvilli supporting the hypothesis that tear fluid components are absorbed. Based on its composition epithelial secretions fulfill functions in tear transport and antimicrobial defense. Further defense mechanisms are displayed by IgA and defense cells which show a special intraepithelial and subepithelial distribution. Moreover, tear duct-associated lymphoid tissue (TALT) is present, displaying the cytomorphological and immunophenotypic features of mucosa-associated lymphoid tissue (MALT). The mechanisms of tear outflow are not yet resolved and several hypotheses exist. Significance is attributed to the lacrimal part of the orbicularis eye muscle surrounding the canaliculi, the helically arranged system of connective tissue fibres and the cavernous body that surrounds the lacrimal sac and the nasolacrimal duct. Moreover, the cavernous body has a function in protecting the lacrimal passage and is active during emotions.

Endoskopowa dacryocystorhinostomia u pacjentów z pozaworeczkowym typem niedrożności dróg łzowych

Dynamic development of the endoscopic treatment of the lacrimal duct obstruction has been observed for the last 20 years. Various causes of the tear outflow disorders, different levels of lacrlmal duct blockage may require different surgical approach and sometimes additional modern equipment. THE AIM of the study was to present the results of treatment of possibly uniform group of patients with lacrimal duct obstruction in whom the same method of endoscopic surgery was applied. 16 patients with postsuccal level of obstruction were qualified for the study. All of them were treated endoscopically with mucosal flap formation. Patients in whom synechiae in the upper part of the sac or at the orifice of common canalicullus were found during the procedure were excluded from the study, as well as the patients with Wagener's granulomatosis and posttraumatic form of lacrimal obstruction. Release of epiphora and proper patency of lacrimal system corroborated by irrigation test was achieved in 14 (87,5%) patients of the studied group. In 2 (12,5%) patients recurrence of symptoms was observed. In both cases too small osteotomy and lack of surgical technique precision were the cause of failure. No major complications in the studied group were observed. Endoscopic dcryocystorhinostomy Is low traumatic and effective procedure of surgical treatment of lacrimal duct obstruction. The success is determined by high precision of surgical technique.

The Ocular Surface: The Challenge to Enable and Protect Vision

The surface of the eye is an extraordinary and vital component of vision. The smooth, wet surface of the cornea is the major refractive surface of the visual system, which, along with corneal transparency, enables light to proceed through the lens and onto the retina for photoreceptor activation. The presence of the smooth, wet refractive ocular surface required for vision comes, however, at a cost. Unlike all other wetsurfaced epithelia of the body, the ocular surface is directly exposed to the outside world where it is especially subject to desiccation, injury, and pathogens. As a consequence, numerous protective mechanisms are provided by the Ocular Surface System, to ensure vision. The Ocular Surface System Maintenance and protection of the smooth refractive surface of the cornea is the function of the Ocular Surface System (Fig. 1). 1 It is defined as the ocular surface, which includes the surface and glandular epithelia of the cornea, conjunctiva, lacrimal gland, accessory lacrimal glands, and meibomian gland, and their apical (tears) and basal (connective tissue) matrices; the eyelashes with their associated glands of Moll and Zeis; those components of the eyelids responsible for the blink; and the nasolacrimal duct. All components of the system are linked functionally by continuity of the epithelia, by innervation, and by the endocrine, vascular, and immune systems. The rationale for the use of the term “Ocular Surface System” is several-fold. First, the primary, synergistic function of the system components is to provide, protect, and maintain a smooth refractive surface on the cornea. Thus, the term Ocular Surface System is linked to its primary function at the ocular surface. Second, all the epithelia at the ocular surface are continuous, with no breaks between regions, and all are derived from the surface ectoderm. The corneal and conjunctival epithelia are continuous, through the ductal epithelium, to the lacrimal glandular epithelium, as is the case with the accessory lacrimal glands, the meibomian gland, and the nasolacrimal system. The glandular systems are essentially involutions from and specializations of the surface epithelium. Communication along these epithelia occurs through gap junctions and cytokines. 2‐4 Third, all regions of the ocular surface epithelia produce components of the refractive tear film; the corneal and conjunctival epithelia produce hydrophilic mucins that hold tears onto the surface of the eye; the lacrimal and accessory lacrimal glands secrete water and a host of protective proteins; the meibomian gland provides the superficial tear lipid layer that prevents tear evaporation. The nasolacrimal epithelial system adsorbs tear components and is believed to, through its cavernous vascular system, control and regulate tear outflow, helping to maintain the appropriate tear level—a fine balance between secretion and outflow. 5 The functions of the various

MUC16 in the lacrimal apparatus

The aim of the present study was to determine the possible expression of the mucin MUC16 in the lacrimal apparatus. Expression and distribution of MUC16 in lacrimal gland, accessory lacrimal glands, and nasolacrimal ducts was monitored by RT-PCR and immunohistochemistry. MUC16 was expressed and detected in all tissues investigated. Comparable to conjunctiva and cornea it was membrane-anchored in accessory lacrimal glands whereas in lacrimal gland acinar cells and columnar cells of the nasolacrimal ducts it was stored in intracytoplasmic vesicles without membrane-association. Subepithelial serous glands of the nasolacrimal ducts revealed staining of the secretion product. Intracelluar production of MUC16 is present in lacrimal gland and epithelial cells of the nasolacrimal ducts but it is not clear whether this MUC16 is secreted. MUC16 seems to be shedded or secreted from the epithelial surface of subepithelial serous glands of the nasolacrimal ducts. Our results show that MUC16 is present in the whole lacrimal apparatus. Its distribution pattern suggests different physiological functions with regard to tear film physiology and tear outflow. Moreover, the results demonstrate the existence of so far not recognized qualitative differences in the secretion product of main lacrimal gland and accessory lacrimal glands (glands of Krause).

Snip Punctoplasty Offers Little Additive Benefit to Lower Eyelid Tightening in the Treatment of Pure Lacrimal Pump Failure

Lacrimal pump failure refers to epiphora due to reduced tear outflow in the presence of a patent lacrimal drainage system and well-positioned puncta. This condition has been managed with dacryocystorhinostomy and lower eyelid tightening, which carry success rates of 50–94% and 84–91%, respectively. In this retrospective study, 23 eyes with symptomatic epiphora attributed to lacrimal pump failure underwent the lateral tarsal strip procedure and lower eyelid snip punctoplasty, and 20 eyes (87%) experienced complete or nearly complete resolution of tearing. This success rate is quite similar to that of prior studies of eyelid tightening alone for lacrimal pump failure, suggesting that the addition of the snip punctoplasty may not offer any additional benefit in patients with little or no punctal stenosis. All patients displayed some degree of lower eyelid laxity on lid distraction testing preoperatively, and those with only mild lid laxity responded at least as well as those with more severe laxity.

Bilateral canaliculitis following SmartPLUG insertion for dry eye syndrome post LASIK surgery

Dry eyes are a common symptom following LASIK corneal refractive surgery. Treatments include topical lubricants to supplement the tear film, and punctal occlusion to reduce tear outflow. Canaliculitis is a recognised complication of punctal plugs, but has not previously been described following insertion of newer generation semi-permanent intra-canalicular plugs, such as the SmartPLUG. Case report. We describe a 60-year-old female who underwent bilateral LASIK surgery leading to aggravation of her dry eye syndrome. She was managed with the insertion of semi-permanent intra-canalicular moldable silicone SmartPLUGs. She subsequently developed bilateral canaliculitis requiring bilateral canaliculotomy. To the best of our knowledge, this is the first report of bilateral canaliculitis following intra-canalicular SmartPLUG insertion. This case illustrates that punctal occlusion with the newer generation intra-canalicular plugs carries a risk of canaliculitis and that irrigation is not always effective in removing these devices.

The adhesion of Pseudomonas aeruginosa to high molecular weight human tear film species corresponds to glycoproteins reactive with Sambucus nigra lectin

Pseudomonas aeruginosa is a pathogen gaining prevalence in contact lens-related corneal ulcers. Tear outflow protects the ocular surface, where high molecular weight tear glycoproteins bind bacteria for removal from the eye. The purpose of the present study was to identify glycoproteins in human tears involved in the adhesion of ocular P. aeruginosa isolates. Basal human tears were applied to a bacterial adhesion assay involving electrophoretic separation of tear components, transfer to nitrocellulose and incubation with biotin-labelled bacteria. Glycoproteins were further characterised using lectin profiling. The results showed large-dimension agarose gels were imperative for the detection of at least four glycoproteins with a migration >200 kDa, including species not previously identified. P. aeruginosa 6294 preferentially bound to a well-defined glycoprotein near the origin of the gel that, unlike other glycoproteins >200 kDa, reacted with Sambucus nigra lectin (sialic acid α2–6) but not WGA lectin ( N-acetylglucosamine, sialic acid α2–3). Adhesion did not involve free biotin label or hydrophobic interactions. Also, the pre-incubation of separated tear glycoproteins with S. nigra lectin increased subsequent adhesion of 6294 to this tear glycoprotein. The less virulent Paer1 strain showed diffuse adhesion in the S. nigra-reactive region at the gel origin. In conclusion, an overlay adhesion assay was developed that identified slow-migrating sialylated glycoprotein species in human tears preferentially bound by P. aeruginosa ocular strains, and S. nigra lectin seemed to enhance the interaction. The study provides a basis for direct investigation of bacterial adhesion to glycoproteins with an apparent migration >200 kDa in tear fluid.

Mucins and TFF peptides of the tear film and lacrimal apparatus

The three-dimensional organization of the tear film, which is produced and drained by the different structures of the ocular adnexa, is essential for maintainance and protection of the ocular surface. This is facilitated by a class of large, highly glycosylated, hydrophilic glycoproteins, the mucins, which are usually expressed in association with a class of peptides having a well-defined, structurally conserved trefoil domain, the mammalian trefoil factor family (TFF) peptides. In this review, the latest information regarding mucin and TFF peptide function and regulation in the human lacrimal system, the tear film and the ocular surface is summarized with regard to mucous epithelia integrity, rheological and antimicrobial properties of the tear film and tear outflow, age-related changes and certain disease states such as dry eye, dacryostenosis and dacryolith formation.

Temporal changes in the tear menisci following a blink

This study investigated tear meniscus formation after a blink. Multiple images of the inferior and superior menisci, viewed en-face, were sequentially captured using a video-slitlamp that permitted the measurement of tear meniscus height (TMH). In a similar manner, tangentially viewed images were obtained of the inferior meniscus so changes in cross-sectional radius of curvature (TMR) with time could be determined. Additionally, the relationship between inferior TMH and tear volume was quantified by the successive instillation of small aliquots of fluid. In this latter experiment the inflow and outflow of tears were controlled by anaesthetizing the ocular surface and inner nose, and use of punctal plugs. The TMH of both menisci rose after a blink ( p < 0.01) by a similar amount ( p = 0.59). This suggests that capillarity is dominant over gravity in tear drainage, however, it may simply reflect that these influences are small compared to the large flow resistances that occur in thin films, hydraulic connectivity between the two menisci, or differences in their anterior-posterior width leading to unequal volume-height relationships. TMR increased with time after a blink ( p < 0.0001); immediately on eye opening the curvature of the inferior meniscus was approximately circular but this soon became eccentric, with the radius of its upper half exceeding that of its lower half. The growth rate of the two menisci slowed with time and this, based on theoretical considerations, is predicted to have occurred primarily because localized thinning of the tear film adjacent to the menisci markedly raised flow resistance. Inferior TMH increased linearly with the cumulative volume of instilled fluid ( r 2 = 0.98), supporting its use in the diagnosis and classification of tear anomalies, although the gradient of this relationship varied between subjects.

A Mathematical Model for Ocular Tear and Solute Balance

Purpose: In this paper we develop a mathematical model that can predict the steady-state tear film thickness and the dynamic tear film thickness and the solute concentration after instillation of a solute-laden fluid in the eye. Methods: The mathematical model developed in this paper is based on a balance between the inflow and outflow of tears into the tear film. It incorporates a tear drainage model and a model that relates the tear film thickness to the meniscus radius of curvature. To predict the solute concentrations, the tear balance is coupled with the solute balance. The differential equations for the unsteady balances are solved numerically. Results: The model predicts that the tear film thickness depends on a number of physiological factors, such as rates of tear production and evaporation, geometry and modulus of the canaliculi, and surface tension and viscosity of tears, and varies from about 3 to 15 μ m. The model also predicts that the drainage time for an instilled volume of 15 μ l is 1283 s. Additionally, the time required for the tracer concentration to decay to 1% of the value immediately after instillation of a drug-laden 40 μ l drop is about 2480 s. Similarly, the time for intensity decay for a radioactive tracer after 25 μ l instillation is about 1566 s. Also, the model predicts that the fraction of the instilled drug that reaches the cornea is about 1.3% for topical application of timolol. Conclusions: The predicted results agree reasonably with the reported experimental results, at least qualitatively. The model developed here can serve as a useful tool to develop a more precise understanding of various issues related to tears and also evaluate the effect of various parameters on the tear volume.

The cavernous body of the human efferent tear ducts contributes to regulation of tear outflow.

To test the hypothesis that the surrounding vascular plexus of the lacrimal sac and the nasolacrimal duct contributes to the regulation of tear outflow. Experiments in 30 probands aged between 15 and 37 years were performed in both nasolacrimal systems of each subject by observing with an endoscope the transit time of an applied tear drop containing fluorescein dye until its entry into the inferior meatus of the nose. Four different experiments were performed to determine the median transit time under normal conditions and the influence on transit time of a decongestant drug, a foreign body on the ocular surface, and a decongestant drug applied together with a foreign body on the ocular surface. Comparisons were made between the right and left nasolacrimal system, in males and females, eyeglass wearers and non-eyeglass wearers, and the different experiments and the results statistically analyzed. The tear transit time was independent of side (right or left), gender, or eyeglass wear. It showed great individual variability. Application of a decongestant drug or placement of a foreign body on the ocular surface both prolonged the dye transit time significantly. Application of a decongestant drug simultaneously with placement of a foreign body shortened the dye transit time significantly compared with the effect of the decongestant drug alone but revealed no significant difference compared with application of a foreign body alone. The cavernous body of the lacrimal sac and nasolacrimal duct plays an important role in the physiology of tear outflow regulation. It is subject to autonomic control and is integrated into a complex neuronal reflex feedback mechanism starting with the dense innervation of the cornea. Moreover, its function can be pharmacologically influenced.

Drainage of Tears: Impact on the Ocular Surface and Lacrimal System

The human efferent tear ducts are part of the lacrimal system. Because little knowledge exists concerning the physiology of the nasolacrimal system, and hence its pathophysiology, the nasolacrimal system has received almost no consideration as a possible factor in dry eye. The human nasolacrimal ducts consist of the upper and the lower lacrimal canaliculus, the lacrimal sac, and the nasolacrimal duct. As a draining and secretory system, the efferent tear ducts play a role in tear transport and nonspecific immune defense. Moreover, components of tear fluid are absorbed in the nasolacrimal passage and are transported into a surrounding vascular system. This system is similar to a cavernous body that is subject to autonomic control and regulates tear outflow. Tear duct-associated lymphoid tissue (TALT) is present in the efferent tear ducts, displaying the cytomorphological and immunophenotypic features of mucosa-associated lymphoid tissue (MALT). Under normal conditions, tear fluid components are constantly absorbed into the blood vessels of the surrounding cavernous body. These vessels are connected to the blood vessels of the outer eye and could act as a feedback signal for tear fluid production, which ceases if these tear components are not absorbed. In this way, dry eye could be initiated. Defective stimulation of TALT could result in abnormal immune deviation at the ocular surface, leading to an autoimmunological response that causes dry eye pathology.

Canalicular stenosis secondary to weekly versus every-3-weeks docetaxel in patients with metastatic breast cancer

Purpose To compare the frequency of canalicular stenosis as a side effect of weekly versus every-3-weeks docetaxel in patients with metastatic breast cancer. Design Retrospective nonrandomized comparative trial. Patients and methods Eighteen patients enrolled in a phase II study of weekly docetaxel plus trastuzumab and 18 patients enrolled in a phase II study of every-3-weeks docetaxel plus doxorubicin were evaluated. Each patient underwent a comprehensive ophthalmologic examination, probing and irrigation of the nasolacrimal duct, and, in some instances, a nuclear lacrimal scan. Main outcome measures If epiphora (excessive tearing) was reported by the patient, its time of onset was documented. In patients with epiphora, presence or absence of canalicular stenosis was evaluated on the basis of the findings on probing and irrigation. The duration of treatment with docetaxel, the dose frequency, and the cumulative dose of docetaxel were recorded in each case. Results Fourteen patients (77%) receiving weekly docetaxel plus trastuzumab had epiphora. Nine of these patients had significant anatomic narrowing of the canaliculi. Bicanalicular silicone intubation or dacryocystorhinostomy was recommended in all nine patients. Eight patients underwent surgery and experienced complete or near complete resolution of epiphora. Although two patients (11%) receiving every-3-weeks docetaxel plus doxorubicin reported transient symptoms of epiphora, neither patient was found to have narrowing of the canaliculi, and the epiphora was not severe enough to justify surgical intervention. The mean duration of docetaxel therapy for the patients in this study was 19 weeks. The mean cumulative dose of docetaxel was higher in patients with canalicular stenosis than in patients without this side effect. Conclusions Canalicular stenosis was more common in patients receiving weekly docetaxel than in those receiving every-3-weeks docetaxel for metastatic breast cancer. Bicanalicular silicone intubation early in the course of weekly docetaxel therapy should be considered, because this intervention can prevent complete closure of the canaliculi. Once complete or near complete stenosis of the canaliculi occurs, placement of a permanent Pyrex glass tube may become necessary to overcome the blockage of tear outflow.

Canalicular stenosis secondary to weekly docetaxel: a potentially preventable side effect

BackgroundThe purpose of this study was to describe canalicular stenosis as a mechanism for epiphora (excessive tearing) secondary to weekly docetaxel. Patients and methodsFourteen patients with metastatic breast cancer who developed epiphora during weekly docetaxel therapy underwent an ophthalmologic examination, and probing and irrigation of the nasolacrimal ducts. The total duration of docetaxel therapy, the duration of treatment at the time of onset of epiphora, the number of infusions, the cumulative dose of docetaxel and the severity of canalicular stenosis were recorded. ResultsAll 14 patients had anatomic narrowing of the canaliculi as the underlying mechanism for epiphora. Bicanalicular silicone intubation or dacryocystorhinostomy (DCR) was recommended for all 14 patients. Eleven patients underwent surgery and experienced resolution of their symptoms. The three patients who declined surgery continue to have epiphora at the time of this report. ConclusionsCanalicular stenosis is an underlying mechanism for epiphora in patients receiving weekly docetaxel. Bicanalicular silicone intubation should be considered early in the course of weekly docetaxel therapy to prevent complete closure of the canaliculi. Once complete or near complete stenosis of the canaliculi occurs, DCR with a permanent pyrex glass tube placement may become necessary to overcome the blockage of tear outflow.

Innervation of the cavernous body of the human efferent tear ducts and function in tear outflow mechanism.

The lacrimal sac and nasolacrimal duct are surrounded by a wide cavernous system of veins and arteries comparable to a cavernous body. The present study aimed to demonstrate the ultrastructure of the nervous tissue and the localisation of neuropeptides involved in the innervation of the cavernous body, a topic not previously investigated. Different S-100 protein antisera, neuronal markers (neuron-specific enolase, anti-200 kDa neurofilament), neuropeptides (substance P, neuropeptide Y, calcitonin gene-related peptide, vasoactive intestinal polypeptide) and the neuronal enzyme tyrosine hydroxylase were used to demonstrate the distribution pattern of the nervous tissue. The ultrastructure of the innervating nerve fibres was also examined by means of standard transmission electron microscopy. The cavernous body contained specialised arteries and veins known as barrier arteries, capacitance veins, and throttle veins. Perivascularly, the tissue was rich in myelinated and unmyelinated nerve fibres in a plexus-like network. Small seromucous glands found in the region of the fundus of the lacrimal sac were contacted by nerve fibres forming a plexus around their alveoli. Many nerve fibres were positive for S-100 protein (S 100), neuron-specific enolase (NSE), anti-200 kDa neurofilament (RT 97), calcitonin gene-related peptide (CGRP), substance P (SP), tyrosine hydroxylase (TH), and neuropeptide Y (NPY). Vasoactive intestinal polypeptide (VIP) immunoreactivity was only demonstrated adjacent to the seromucous glands. Both the density of nerve fibres as well as the presence of various neuropeptides emphasises the neural control of the cavernous body of the human efferent tear ducts. 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, malfunction in the innervation of the cavernous body may lead to disturbances in the tear outflow cycle, ocular congestion or total occlusion of the lacrimal passages.

Excessive tearing in infancy and early childhood

PREVIEWObstruction of tear outflow is a primary cause of excessive tearing in infants and young children. In this review of a common disorder, Dr Ballard explores the causes and anatomic and physiologic features of excessive tear flow in pediatric patients. Criteria for the differential diagnosis of overflow tearing are featured, and noninvasive and surgical techniques for the treatment of obstructions to nasolacrimal drainage are presented.