Valvular system of the lacrimal drainage pathway and the valve of Rosenmüller.

The valves of the lacrimal drainage system are an enigma with a rich eponymous history. The unidirectional flow of tears along with the ultrastructural demonstration of distinctive mucosal folds on the luminal surface has rekindled an interest in them. The first in vivo direct demonstration of the valve of Rosenmüller and its functions has laid to rest some of the controversies of its existence and that of the valve of Huschke. The dynamic assessment of the valve of Rosenmüller has shown a well-defined functional role in the facilitation of unidirectional tear flow. The present mini review describes the embryological aspects, brief overview of the eponymous valves, techniques for their identification along with recent structural and functional aspects of the valve of Rosenmüller.

Scanning Electron Microscopic Features of the Canalicular Entrance Into the Lacrimal Sac.

PURPOSE: The aim of this study was to examine the ultrastructural features of the canalicular entrance into the lacrimal sac. METHODS: Ten openings of the common canaliculus into the lacrimal sac from 10 lacrimal sacs obtained during a dacryocystectomy were studied. Each of the openings were completely excised with 3-4 mm margins on all sides and transported to the laboratory in 2.5% glutaraldehyde. The analysis was performed using the standard protocols of scanning electron microscopy (SEM). The openings, their edges, canalicular lacrimal sac-mucosal folds, and internal surfaces were studied. RESULTS: Of the 10 common canalicular openings studied, the upper and lower canaliculi opened into a common canaliculus in all the cases. The terminal portion of the 2 canaliculi had a common wall, which appeared like a septum, just proximal to the beginning of the dilated common canalicular portion. In 60% (6/10) of the cases, a diverticular or a type III sinus of Maier (SOM) was noted. The surface of this diverticulum was smooth and lined by stratified columnar epithelium, reflecting its lacrimal sac origins. Interestingly, the junction of the epithelial change from stratified squamous to columnar could be appreciated clearly in 80% (8/10) of the cases and was mostly located just within from the edge of the internal common opening (ICO). The canalicular lacrimal sac-mucosal folds could be appreciated in 70% (7/10) samples, being very defined and prominent in 30% (3/10). CONCLUSIONS: The common merged wall of the 2 canaliculus is the most proximal and prominent structure noted on an end-on view of the ICO. Diverticular variant of the sinus of Maier is common. The junction of the epithelial change from stratified squamous to columnar is appreciated just within the edge of the ICO.Detailed anatomical features of the common canalicular opening into the lacrimal sac can help our understanding of the focal anatomy and tear rheology.

Ultrastructure of the lacrimal drainage system in health and disease: A major review.

PURPOSE: To provide a systematic review of the literature on the ultrastructural findings of the lacrimal drainage system in healthy state and in few of the disorders studied so far. METHODS: The authors performed a PubMed search of all articles published with reference to electron microscopic features of the lacrimal drainage pathways. Data captured include demographics, study techniques, scanning or transmission electron microscopic features, presumed or confirmed interpretations and their implications. Specific emphasis was laid on addressing the lacunae and potential directions for future research. RESULTS: Ultrastructural studies have led to better understanding of the lacrimal drainage anatomy-physiology correlations. Cellular interactions between fibroblasts and lymphocytes could form a basis for pathogenesis of punctal stenosis. Ultrastructural characterization of peri-lacrimal cavernous bodies and changes in primary acquired nasolacrimal duct obstruction (PANDO) led to them being partly implicated in its etiopathogenesis. Electron microscopic characterization of the dacryolith core promises insights into their evolution. Ultrastructural tissue effects of mitomycin-C during a DCR surgery has provided potential evidence of its role in cases with high-risk of failure. Lacrimal stent biofilms are common but their clinical implications are currently uncertain. CONCLUSION: Ultrastructural exploration of lacrimal drainage system so far has been limited and sparsely explored. The list of unexplored areas is exhaustive. There is a need for the lacrimal Clinician-Scientist to make themselves familiar with techniques and interpretation of electron microscopy to advance the ultrastructural frontier of this science.

Scanning Electron Microscopic Features of the Inferior Meatal Nasolacrimal Duct Openings.

PURPOSE: The aim of this study was to examine the ultrastructural features of the nasolacrimal duct (NLD) openings in the inferior meatus. METHODS: Five openings of the NLD in the inferior meati from 5 sagittal head sections of 3 cadavers were studied. Each of the openings were completely excised with 2 mm margins on all sides and transported to the laboratory in 2.5% glutaraldehyde. The analysis was performed using the standard protocols of scanning electron microscopy. The ends, edges, and surfaces were studied along with the mucosal folds, if any, guarding the edge of the openings. RESULTS: Of the 5 NLD openings studied, 4 were of the sulcus variety and 1 was of the shape of a fissure. The fissure opening had a guarding anterior edge mucosal fold. The luminal surfaces of the openings were mostly smooth with focal defined glandular structures. Occasional heterogenous areas with prominent and extensive well-defined glands lined by ciliated columnar epithelium were noted. There were presence of mucosal folds on the floor of the sulci of the openings giving an appearance of a subsulcus. CONCLUSIONS: The luminal surfaces of the NLD openings in the inferior meati shows mucosal folds reflected on themselves and cavernous vessels throughout the expanse of the openings. Tear rheology at the NLD opening and the physiologic role of subsulci need to be investigated further.

Histopathology, Immunohistochemistry, and Electron Microscopic features of a Dacryocystorhinostomy Ostium Cicatrix.

PURPOSE: The aim of this study is to report the histopathological, Immunohistochemical, and ultrastructural features of a dacryocystorhinostomy ostium cicatrix. METHODS: A prospective histopathological study was performed in a tertiary eye care setting. Scarred nasal mucosal tissues obtained during endoscopic revisions of 10 previously failed dacryocystorhinostomies secondary to complete cicatricial closure of the ostia were studied. The tissue specimens were analyzed using hematoxylin and eosin, periodic acid-Schiff staining. Special stains used include Masson's trichrome and Alizarin red. Immunohistochemistry was performed using vimentin, smooth muscle actin, CD3, CD5, and CD20. Specimens were processed for ultrastructural analysis as per standard protocols for transmission electron microscopy. RESULTS: The respiratory epithelial regeneration was noted to be complete. Irregular laying of deeply eosinophilic and hyalinized collagen with intervening fibroblasts was noted. Focal areas of new bone formation were seen within the cicatricial tissue with osteocytes and ongoing osteoblastic rimming. The infiltrates were mixture of both T and B lymphocytes and were positive for CD3, CD5, and CD20 immunostaining. Electron microscopy showed disorganized collagen fibrils with numerous fibroblasts and mononuclear inflammatory infiltrate. Amorphous bony osteoid within a fibrillar background with metabolically active osteoblasts showed a vesicular cytoplasm, hyperplastic proliferating mitochondria, large Golgi apparatus, and dense endoplasmic reticulum. CONCLUSION: There is new bone formation within the dense connective tissues of a dacryocystorhinostomy cicatrix. This study may provide useful inputs for further basic science studies aimed at better understanding of wound healing in failed dacryocystorhinostomy.

Electron Microscopic Features of Intraluminal Portion of Nasolacrimal Silastic Stents Following Dacryocystorhinostomy: Is There a Need for Stents Without a Lumen?

AIM: The aim of this study was to examine the presence of biofilms and physical deposits within the lumen of silastic nasolacrimal duct stents inserted during dacryocystorhinostomy. METHODS: A prospective interventional study was performed on consecutive patients undergoing endoscopic dacryocystorhinostomy with Crawford stent insertion. All the patient samples were retrieved 4 weeks after the surgery. None of the patients had any clinical evidence of postoperative infection. The intraluminal portions studied include the distal cut ends and the entire intraluminal surface. The analysis was performed using the standard protocols of scanning electron microscopy. The luminal surfaces were compared against sterile stents that acted as controls. RESULTS: A total of 7 stents were studied. Five were consecutive patient samples and 2 were sterile stents. The cut ends and intraluminal surfaces of all the patient stents demonstrated evidence of biofilm formation and physical deposits. The luminal cut ends demonstrated extensive deposits and thick mixed biofilms constituted by fungal filaments and bacteria. The entire stretch of intraluminal surfaces showed thin, fine layers of deposits and bacterial biofilms with skip areas. CONCLUSIONS: Intraluminal surfaces of lacrimal stents harbor physical deposits and mixed biofilms. Because the purpose and functions of stents are not influenced by the presence or absence of its lumen, the use of nonluminal stents may prevent additional surfaces from acting as nidus for microbes.

Scanning Electron Microscopic Features of the External and Internal Surfaces of Normal Adult Lacrimal Drainage System.

AIM: The aim of this study was to examine the ultrastructural features of the external and internal surfaces of healthy lacrimal drainage systems. METHODS: A prospective interventional study was performed on the healthy adult lacrimal drainage systems obtained from fresh exenterated specimens. Exenteration was performed for malignancies unrelated to lacrimal system where preoperative lacrimal evaluation was normal. A careful and thorough dissection was carried out to isolate the entire lacrimal drainage system from the punctum to the nasolacrimal duct. The analysis was performed using the standard protocols of scanning electron microscopy. RESULTS: Inner punctal surfaces showed a definite and slightly elevated junction between the luminal surfaces of punctum and beginning of the vertical canaliculus. Similar junction could be identified between the lacrimal sac and nasolacrimal duct. The valves of the canaliculi showed broad rugae-like mucosal surfaces, whereas the external surfaces of the canaliculi demonstrated well-defined orbicularis muscle with collagenous attachments. The walls of the lacrimal sac and nasolacrimal duct showed dense vascular plexus which included wide luminal arteries, throttle veins, and large capacitance vessels. CONCLUSIONS: Ultrastructural features of external and internal surfaces of lacrimal drainage system help in better understanding of its anatomy and physiology. The junctional area between the punctum-vertical canaliculus and lacrimal sac-nasolacrimal duct needs further exploration to understand their roles.

Comparative anatomy of the human and canine efferent tear duct system--impact of mucin MUC5AC on lacrimal drainage.

PURPOSE: To investigate the histomorphology of the canine tear drainage system and to show the distribution of mucin MUC5AC within the tissue. METHODS: Conjunctiva and tear drainage systems of 19 long-nosed dogs were investigated histologically and ultrastructurally. The tissues were stained with eight different antibodies reactive against less glycosylated and highly-glycosylated MUC5AC. Results were compared with findings in human tissue received from 12 body donors. RESULTS: Except for a distinctly longer nasolacrimal duct and several accessory openings of the duct into the nasal cavity, the morphology of the canine tear drainage system is very similar to that of humans. MUC5AC in less- and highly-glycosylated forms was present in the conjunctival tissue of dogs as well of humans. Within the tear sac and the nasolacrimal duct only less-glycosylated MUC5AC could be found in dogs and in human. CONCLUSIONS: These findings demonstrate that the canine tear drainage system is very similar to its human equivalent. In particular the distribution of MUC5AC, supposed to play an important role within the pathogenesis of dry eye syndrome (DES), is the same as in humans. Therefore the canine model seems to be an appropriate model for further DES research.

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.

New insights into the pathophysiology of primary acquired dacryostenosis.

OBJECTIVE: To obtain new insights into the pathophysiology of primary acquired dacryostenosis. DESIGN: Comparative autopsy tissue study with histopathologic correlations. MATERIALS: Tissue specimens from the human nasolacrimal ducts of 36 patients undergoing endonasal dacryocystorhinostomy within a framework of primary acquired dacryostenosis were analyzed by histologic studies and electron microscopic examination. Six lacrimal systems of body donors served as controls. TESTING: One group of tissue specimens from each lacrimal system was prepared and processed with paraffin, sectioned, stained by different methods, and finally examined by light microscopy. The other group was processed with araldite after preparation, sectioned semithin and ultrathin, and examined by transmission electron microscopy. MAIN OUTCOME MEASURES: The degree of dacryostenosis was scored in each tissue specimen by grading the histologic sections as mild (active chronic inflammation), moderate (proliferative sclerotic forms of chronic fibrosis), or severe (total subepithelial fibrosis). RESULTS: Of 36 patients with epiphora, 13 had functional obstruction with a patent lacrimal system on syringing; in 23 cases, the lacrimal passage was completely obstructed. Different pathologic stages correlating to duration of symptoms were found ranging from active chronic inflammation to proliferative sclerotic forms and total subepithelial fibrosis. CONCLUSIONS: Descending inflammation from the eye or ascending inflammation from the nose initiates swelling of the mucous membrane, remodeling of the helical arrangement of connective tissue fibers, malfunctions in the subepithelial cavernous body with reactive hyperemia, and temporary occlusion of the lacrimal passage. In the follow-up, repeated isolated occurrence of dacryocystitis leads to structural epithelial and subepithelial changes, which may lead either to a total fibrous closure of the lumen of the efferent tear duct or to a nonfunctional segment in the lacrimal passage that is manifest on syringing.

The cavernous body of the human efferent tear ducts: function in tear outflow mechanism.

PURPOSE: To determine the structure and function of a system of large blood vessels integrated in the bony canal between the orbit and the inferior nasal duct. METHODS: Thirty-one dissected lacrimal systems of adults were analyzed by using gross anatomy, histology, and electron microscopy as well as corrosion vascular casts. RESULTS: More than two thirds of the bony canal between orbit and inferior nasal duct is filled by a plexus of wide-lumened veins and arteries. The vascular system is embedded in the wall of the lacrimal sac and nasolacrimal duct and is connected to the cavernous tissue of the inferior turbinate. Three types of blood vessels can be distinguished inside the vascular tissue that surrounds the lumen of the lacrimal passage: barrier arteries, capacitance veins, and throttle veins. CONCLUSIONS: The surrounding vascular plexus of the lacrimal sac and nasolacrimal duct is comparable to a cavernous body. While regulating the blood flow, the specialized blood vessels permit opening and closing of the lumen of the lacrimal passage, effected by the bulging and subsiding of the cavernous body, and at the same time regulate tear outflow. Other functions such as drainage of absorbed tear fluid components and a role in immunologic response are under discussion as well. Malfunctions in the cavernous body may lead to disturbances in the tear outflow cycle, ocular congestion, or total occlusion of the lacrimal passages. Variations in the conditions for swelling of the cavernous tissue may have led to the (mistaken) description of valves in the lacrimal passage.

[Ultrastructural aspect of the different levels of the lacrimal system (author's transl)]. / Les cellules ciliées du système lacrymal. Ultrastructure comparée de la muqueuse lacrymale.

Using the transmission electron microscope and the scanning electron microscope, we have found a different ultrastructure at the different levels of the lacrimal system: 1) tarsal conjonctiva: numerous microvilli on a relief of small valleys; 2) lacrimal punctum: the surface of the cell is flat with sparse microvillosti, sparse cilia and strong intercellular junction; 3) external part of the canaliculus: pavement epithelium with numerous microvillositi and pinocytosis, absence of cilia; 4) internal part of the canaliculus: the microvillositi are very small or absent; 5) lacrimal sac: the cilia are arranged by tufts scattered on this malpighian epithelium; 6) nasolacrimal duct: the cilia are numerous; 7) in the nose the cilia are extremely numerous.

[The cilia of the lacrimal sac epithelium SEM studies (author's transl)]. / Die Flimmerhaare des Tränensackepithels (Rasterelektronenmikroskopische Untersuchungen)

On the basis of SEM studies it has been shown that the cilia are arranged into groups of 10 to 40 in the individual epithelial cells of the lacrimal sac. The cilia have a length of 15 to 20 micron.