Rigid GRIN-endoscope for endoscopy of the tear ducts

BACKGROUND: Using small endoscopes it is now possible to evaluate the status of lacrimal ducts in vivo. GRIN-Lenses produce better pictures from the lacrimal ways than fiber-bundles. GRIN-endoscopes are rigid. The present study is concerned with the feasibility and indications of such GRIN-endoscopic examination. PATIENTS AND METHODS: Two different GRIN-endoscopes with a distal diameter of 0.89 mm were used. One with a phi 0.5 mm optic and an additional working channel and another one with a phi 0.35 mm optic and two additional working channels. One channel each was used for injection of air or 0.9% NaCl. Either a laser fiber or another instrument (max phi 0.16 mm) could be introduced into the second channel. 44 patients in age between 18 and 87 with symptoms of epiphora or signs of chronic lacrimal way affections were examined. RESULTS: The presaccal lacrimal ducts could be clearly visualized in all patients. In case of presaccal stenosis, the examination of the lacrimal sac was not always possible. The endoscope used, based of GRIN-lenses, gave an excellent image quality. Endoscopy under local anesthesia was well tolerated by all the patients with affection of the lacrimal drainage system. Because this ambulant examination does not stress the patient too much, it could be repeated a number of times. Endoscopy under general narcosis could enlarge the application spectrum. This method can complement the ambulant diagnostics and therapy of the lacrimal drainage system.     

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

PURPOSE: To test the hypothesis that the surrounding vascular plexus of the lacrimal sac and the nasolacrimal duct contributes to the regulation of tear outflow. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.     

Functional anatomy of the human efferent tear ducts: a new theory of tear outflow mechanism

· Background: The mechanism of lacrimal drainage under physiological conditions is controversial. The aim of this study was to analyze the three-dimensional architecture of human efferent tear ducts from functional and clinical points of view. A new theory of tear outflow is discussed. · Methods: Thirty-two prepared lacrimal systems of adults were examined by histological, immunohistochemical and scanning electron microscopic techniques. · Results: The wall of the lacrimal sac is made up of collagen bundles, elastic and reticular fibers arranged in a helical pattern. Wide luminal vascular plexus are embedded in this helical system and connected to the cavernous tissue of the inferior turbinate in the region of Hasner’s valve. Immunohistochemical analysis showed evidence of type I and type III collagen as well as chondroitin 4- and 6-sulfate. · Conclusion: With blinking, the lacrimal part of the orbicularis muscle contracts. The fornix of the sac moves in a cranial-lateral direction. Thus the lacrimal sac distends and may be ’’wrung out’’ due to its medial attachment and helically arranged fibrillar structures. The vascular plexus may play an important role in the absorption and drainage of lacrimal fluid. Received: 23 January 1998 Accepted: 27 March 1998     

The lipid layer of the lacrimal tear film: physiology and pathology]

The preocular tear film (POTF) is composed of a deep aqueous-mucin phase that supports a thin superficial lipid phase. The tear lipid layer (TLL), although thin, stabilizes the POTF providing a 25% surface-tension decrease and a 90-95% aqueous evaporation reduction. TLL is formed from lipids secreted by tarsal meibomian glands and spread onto the ocular surface by blinking. The TLL itself is composed of two phases. A thin and deep polar phase, adjacent to the aqueous-mucin layer, has a surfactant role. A thicker and superficial nonpolar phase has antievaporative properties. At the same time, tear lipocalins help the TLL spread and stabilize the lipid-aqueous interface. For clinical examination, TLL is directly observed with the Tearscope. POTF stability and the evaporation rate depend on the lipid layer pattern. When chronic, POTF qualitative trouble (evaporative syndrome) due to a TLL anomaly, leads to secondary ocular surface impairment with increased tear instability and self-propagation of ocular dryness. Meibomian gland dysfunction (MGD) results from local pathology, dermatologic disease (ocular rosacea) or iatrogenic etiology. Cosmetic use is the other principal cause of TLL destabilization. Lid hygiene is the mainstay of MGD treatment. Systemic antibiotics (cyclins) can be associated in cases of severe symptoms. Topical treatment is useful if there is marginal lid inflammation or infection.     

Role of the tear film in the optical quality of the human eye

This paper reviews recent studies of the role of the tear film in the optical quality of the eye. Recent investigations focus on the dynamics of the tear film after a blink and its important role in the optical quality of the eye. The results in this review were used in an attempt to understand the optical and visual impact of tear-film breakup in normal eyes and dry eyes. It was noted that patients with dry-eye syndrome have large optical aberrations compared with those in normal eyes, which may be the cause of blurry vision associated with the syndrome. In addition, instillation of artificial tears reduces optical aberrations and thus improves the optical quality of vision in these patients.     

Animal model for the absorption of lipophilic substances from tear fluid by the epithelium of the nasolacrimal ducts

PURPOSE: To compare the nasolacrimal tissues of several species to see how closely they resemble the human and to measure nasolacrimal absorption of a substance, to show that an absorption pathway exists for substances placed in the external eye, other than directly through the cornea or conjunctiva. METHODS: The nasolacrimal systems of six different vertebrates were investigated by light microscopy to find a species with a nasolacrimal system comparable to that of humans, for use in absorption experiments. In addition to primates, rabbits were revealed by histology to have a lacrimal system closely comparable to that of humans. The rabbit lacrimal system had a stratified epithelium consisting of two layers. Subepithelially, the lamina propria was composed of two strata: loose connective tissue containing elastic fibers and lymphatic cells and a rich venous plexus comparable to a cavernous body. Rabbits were therefore chosen for the absorption experiments. (3)H-cortisol was dropped into the eyes of female rabbits. After 21, 43, or 146 minutes, the rabbits were killed, the blood collected, and the nasolacrimal systems prepared and embedded for histologic examination. Serum was obtained from the clotted blood, and radioactivity was counted. Autoradiographs of sections of rabbit nasolacrimal duct were also prepared. RESULTS: Uptake of radioactivity into the serum was high and increased with time. After 21 minutes, maximum incorporation of the applied radioactivity into the blood the level was 7.1%; after 43 minutes, 12.4%; and after 146 minutes, 15.5%. Transport of radioactivity was visualized in autoradiographs of rabbit nasolacrimal systems. CONCLUSIONS: (3)H-cortisol is incorporated from the nasolacrimal ducts into the blood of rabbits. The comparable morphology of rabbits and humans suggests that absorption of cortisol would also take place in humans. Future investigations of the nasolacrimal passage are needed to understand whether absorption of normal tear fluid components in the nasolacrimal ducts is a physiological function that also plays a role in pathologic conditions such as dry eye. The similarities between rabbit and human nasolacrimal ducts support the use of the rabbit for such studies.     

Role of tear fluid in the growth of Gram-negative bacteria on contact lenses

Incidents of CLARE (contact lens induced acute red eye) are associated with high numbers of Gram-negative bacteria on the lens surface. This study found that most strains of bacteria implicated in CLARE adhere poorly to the lens surface regardless of whether the lens surface was clean or had been worn in the eye. The high numbers of bacteria on the lens surface result from bacterial growth on the lens surface after adhesion has occurred. Using an artificial tear formulation and real tears, this study demonstrated that the tear fluid provides the necessary nutrients required for bacterial growth.     

Role of tear secretory IgA in hard contact lens-related changes in the tarsal conjunctiva.

The role of tear secretory IgA in contact lens-related conjunctival changes was investigated in 40 subjects (80 eyes) who wore polymethyl methacrylate (PMMA) contact lenses and 10 subjects (20 eyes) who did not wear contact lenses. The eyes in the contact lens group had significantly higher tear IgA levels than the control eyes (p < 0.05). We were not able to demonstrate a relation between increased IgA levels and the presence of symptoms or duration of contact lens wear. Increased IgA levels were correlated to papilla formation in the contact lens group. A rise in tear IgA levels seems to be the first abnormal change related to papilla formation in patients who wear PMMA contact lenses.     

Growth factors in the tear film: role in tissue maintenance, wound healing, and ocular pathology

Numerous biologically active growth factors are secreted by the lacrimal gland and distributed via the tears over the ocular surface, where they affect cellular proliferation, migration, differentiation, and survival. The role of growth factors and their receptors in maintenance of tissue homeostasis and wound healing continues to be elucidated, and the effect of growth factor imbalances in ocular surface diseases is just beginning to be understood. For instance, in eyes with ocular surface diseases, including conjunctivitis, corneal erosion, keratitis, and corneal ulcers, epidermal growth factor release rates have been shown to be significantly lower than in normal eyes during reflex tearing. Future research into the mechanisms of dry eye disease will focus on reasons for decreased tear and growth factor production in the neuronal reflex loop or the acinar lacrimal gland cells. Animal models to test therapeutic approaches must be developed.     

New insight into lacrimal gland function: Role of the duct epithelium in tear secretion

Tear secretion is a complex process with the involvement of the main and accessory lacrimal glands, corneal and conjunctival epithelial cells and the Meibomian glands. The lacrimal gland is the main source of fluid, electrolytes and proteins in tear fluid. Deficient ion and water secretion results in aqueous deficient dry eye with serious consequences on the integrity of the ocular surface. Functions of acinar cells are widely studied, whereas less information is available about the duct system of the lacrimal gland. Secretory mechanisms of duct epithelium may play an important role in tear production, but only limited studies have tried to elucidate the role of the duct system in tear secretion. Significant progress has been made in the past few years, resulting in new insight into lacrimal gland duct function. New experimental techniques were introduced, which contributed to the exploration of the role of lacrimal gland ducts in more detail. Therefore, the aim of this review is to summarize our present knowledge about the role of ducts in lacrimal gland function and tear secretion, which appears to be the first review with a focus on this topic. Short outline of pancreatic and salivary gland duct functions is also given for the purposes of comparison.     

泪液渗透压在干眼发病机制中的作用及诊疗进展

干眼是一种以眼表稳态丧失,泪膜不稳定性增加为特征的多因素疾病,伴有眼干涩、异物感、灼烧感、眼红、疼痛、畏光、流泪、眼疲劳、视力下降、分泌物增多、对外界刺激敏感等眼部症状,其病理生理机制主要是泪膜不稳定、泪液渗透压(tear osmolarity, Tosm)升高、眼表炎症和损伤及神经感觉异常。Tosm是维持泪膜稳定性和眼表舒适度的重要因素。Tosm升高可造成干眼患者眼部不适、角膜上皮损伤、杯状细胞丢失及眼部炎症反应,炎症反应可进一步降低泪膜稳定性和增加Tosm,使干眼陷入恶性循环。为了更全面地了解泪液高渗(tear hyperosmolarity, THO)与干眼的关系,本文将从病理生理学方面,重点讨论THO在干眼发病机制、干眼诊断、干眼严重程度分级中的作用,及其针对性治疗。