Internal vascular anatomy of the human lacrimal gland: A protocol based on cadaver dissection and three-dimensional micro-computed tomography.

PURPOSE: To evaluate the feasibility of studying the vascular supply of the orbital and palpebral lobes of the human lacrimal gland using micro-computed tomography (micro-CT) and microscopic dissection. METHODS: The lacrimal gland artery of a fresh parasagittalized cadaver head (male, aged 76 years) was infused with a lead oxide-latex mixture near the occipital pole of the gland. The entire lacrimal gland was imaged using micro-CT and 3D cinematic rendering (CR) and then dissected under a surgical microscope. RESULTS: Micro-CT and CR images showed well-demarcated internal vascular branches of the lacrimal artery and their distribution within the orbital and palpebral lobes. The entire course of the artery and its branches could be visualized by CR and microscopic dissection, with the former showing better spatial orientation and finer branching. The main artery runs along the free edge of the aponeurosis of the levator palpebrae superior muscle and lies in the isthmus portion of the gland (between the orbital and palpebral lobes). The branches of the main lacrimal artery include one branch to the orbital adipose tissue just before entering the gland, two branches to the orbital lobe (medial and lateral), and two branches to the palpebral lobe (medial and lateral). The main artery terminates as palpebral and orbital lobe branches in the lateral half of the lacrimal gland. CONCLUSION: Latex and contrast-enhanced micro-CT is very well suited to visualize the vascular anatomy of the lacrimal artery within the gland. A large number of lacrimal gland examinations using the method presented here are required to demonstrate and understand the variability of the vascular anatomy of the human lacrimal gland.

Morphological and functional relationship between the orbital gland and olfaction in Upupa epops (hoopoe) and Bubulcus ibis (cattle egret).

This study used both anatomical and histological techniques to investigate the orbital gland's topographic relationship with the surrounding system, using the hoopoe and cattle egret as biological models. Hoopoe has a spindle-shaped lacrimal gland that is suspended on the lateral edge of the frontal bone, whereas cattle egret has a tiny lacrimal gland that is embedded posteriorly within the periorbital fascia. The hoopoe's lacrimal gland has a single duct that runs parallel to the nasolacrimal duct and opens into the posterior nostril hole. In the cattle egret, the tubule-alveolar secretory components comprise neutral and acid glycosaminoglycan. In addition, the Harderian gland is found in both these species, but their draining ducts differ; the Harderian gland of the hoopoe opens into the anterodorsal to the conjunctival fornix, whereas the Harderian gland of the egret opens anteriorly. In both hoopoe and egret, the secretions of Harderian gland include neutral and acid glycosaminoglycan. The Harderian gland is categorized as type II in hoopoe and type I in cattle egrets. The present results concluded that both orbital glands of two bird species studied play an essential role in eye health, where cleaning and lubrication of the cornea surface. Furthermore, the lacrimal gland's location and secretory features may strengthen the olfactory sensitivity of hoopoe, which relies heavily on scent to locate their food, whereas egret relies heavily on visual cues.

Histological and histochemical characteristics of lacrimal glands in beluga whales (Delphinapterus leucas).

The objective of this study was to describe the histological and histochemical characteristics of the lacrimal glands of beluga whales. The study was carried out on the formalin-fixed ocular globes from 96 carcasses of beluga whales found stranded in the St. Lawrence estuary in Quebec, Canada. Hematoxylin and eosin (H&E) stained slides from the eyes of each whale were examined for lacrimal glands. Histological description was done with H&E and Masson Trichrome (MT) stains. Period Acid-Schiff (PAS), Alcian blue (AB) pH 1.0 and 2.5, and High Iron Diamine (HID) stains were used for histochemical characterization of glycoproteins. Thirteen ocular samples from animals ranging from neonate to 48 y included sections of lacrimal glands. The H&E stain revealed a tubuloalveolar gland architecture, separated into lobules by dense connective tissue. Each lobule contained a mixture of acini and tubules with ductules. Small and large acini were composed of low and tall columnar cells, respectively. Acinar cells contained basophilic cytoplasmic granules. The ductules were lined with a bi-layered cuboidal-to-squamous epithelium. The MT stain highlighted the connective tissue separating ductules and acini. Large acini were positive for PAS and some small acini had patchy uptake. Positive staining for AB pH 1.0 and 2.5 was mainly seen in tall columnar cells as compared to small acini that had faint to no stain uptake. High Iron Diamine stain revealed 90% staining of all acinar cells, with 10% exhibiting a mixed blue-black tinge. It was concluded that the lacrimal glands of beluga whales have similar histological and histochemical findings to those of artiodactyla and carnivora orders.

L'objectif de cette étude était de décrire les caractéristiques histologiques et histochimiques des glandes lacrymales des bélugas. L'étude a été réalisée sur les globes oculaires fixés au formol de 96 carcasses de bélugas trouvées échouées dans l'estuaire du Saint-Laurent au Québec, Canada. Des lames colorées à l'hématoxyline et à l'éosine (H&E) des yeux de chaque baleine ont été examinées pour la présence de glandes lacrymales. La description histologique a été réalisée avec des colorations H&E et trichrome de Masson (MT). Les colorations Periodic acid-Schiff (PAS), au bleu Alcian (AB) pH 1,0 et 2,5, et diamine à haute teneur en fer (HID) ont été utilisées pour la caractérisation histochimique des glycoprotéines. Treize échantillons oculaires provenant d'animaux allant du nouveau-né à 48 ans comprenaient des sections de glandes lacrymales. La coloration H&E a révélé une architecture de glande tubulo-alvéolaire, séparée en lobules par un tissu conjonctif dense. Chaque lobule contenait un mélange d'acini et de tubules avec des ductules. Les petits et les grands acini étaient respectivement composés de cellules cylindriques basses et hautes. Les cellules acinaires contenaient des granules cytoplasmiques basophiles. Les canaux étaient tapissés d'un épithélium cuboïde à squameux bicouche. La coloration MT a mis en évidence le tissu conjonctif séparant les canaux et les acini. Les grands acini étaient positifs pour le PAS et certains petits acini avaient une absorption inégale. Une coloration positive pour AB pH 1,0 et 2,5 a été principalement observée dans les cellules cylindriques hautes par rapport aux petits acini qui avaient une absorption de coloration faible ou nulle. La coloration HDI a révélé une coloration de 90 % de toutes les cellules acinaires, 10 % présentant une teinte mixte bleu-noir. Il a été conclu que les glandes lacrymales des bélugas présentent des résultats histologiques et histochimiques similaires à ceux des ordres des artiodactyles et des carnivores.(Traduit par Docteur Serge Messier).

Imaging and anatomical parameters of the lacrimal punctum and vertical canaliculus using optical coherence tomography.

Purpose: The anatomical parameters of normal lacrimal puncta and vertical canaliculus using optical coherence tomography (OCT) and the OCT imaging features of punctal lesions were analyzed to provide a basis for clinical diagnosis and treatment. Methods: From June to September 2019, 40 volunteers (80 eyes) from Tongji Hospital were enrolled. The external punctal diameter (ELP) was measured using slit-lamp microscopy and OCT. The internal lacrimal punctal diameter (ILP) at 100 µm, vertical canalicular length (VCL), and tear meniscus depth were measured by OCT with open eyes. Twenty-eight volunteers (56 eyes) underwent the same examinations with their eyes closed. The OCT imaging features of 26 patients (27 eyes) with lacrimal lesions were examined. Results: The ELP of the right and left healthy eyes under slit-lamp microscopy were 564.40 and 555.40 µm respectively. Under OCT, the ELP, ILP, and VCL of the right and left eyes were 628.20 um and 616.85 µm, 343.40 µm and 346.95 µm, 731.95 um and 709.20 µm respectively. The ELP was larger when measured by OCT than slit-lamp microscopy (p<0.05). Twenty-eight volunteers (56 eyes) had measurements taken under different conditions. The ELP, ILP, and VCL of the open and closed right eyes were 667.54 and 567.21 µm, 369.18 and 303.18 µm, 715.00 and 417.14 µm, respectively. The ELP, ILP, and VCL of the open and closed left eyes were 655.86 um and 551.68 µm, 369.25 um and 313.54 µm, 719.96 um and 433.89 µm respectively. The anatomical parameters of the open eyes were greater than those of the closed eyes (p<0.05). Thus, we identified the imaging features of lacrimal stenosis, punctal obstruction, punctal tear, lacrimal atresia, and lacrimal mass using OCT. Conclusions: OCT can be used to measure the anatomical parameters of lacrimal puncta and vertical canaliculus in vivo. In addition, OCT can detect punctal lesions in vivo and provide an objective basis for the clinical diagnosis and treatment of punctal lesions.

Orbital lymphatic vessels: immunohistochemical detection in the lacrimal gland, optic nerve, fat tissue, and extrinsic oculomotor muscles / Vasos linfáticos orbitários: identificação imunohistoquímica na glândula lacrimal, no nervo óptico, no tecido adiposo e nos músculos extrínsecos oculomotores

ABSTRACT Purpose: To identify the lymphatic vessels in orbital specimens from human cadavers using light microscopy and immunohistochemical analysis. Methods: A postmortem study included 10 orbital specimens from 10 human cadavers. The orbital specimens were obtained no later than 12 hours after death. The orbital specimens were dissected into lacrimal gland, optic nerve, fat tissue, and oculomotor muscles. The histologic criteria to qualify as a lymphatic vessel were thin-walled channels of endothelium without a well-developed basal membrane and with an erythrocyte-free, irregular lumen. The immunohistochemical criteria were irregularly shaped, thin-walled vessels with an erythrocyte-free, irregular lumen and immunopositivity for podoplanin D2-40. Results: The lacrimal gland, optic nerve, fat tissue, and extraocular muscle sections were positively stained with podoplanin D2-40. Conclusions: This study demonstrated lymphatic vessels in the human orbit, more precisely, in the lacrimal gland, dura mater of the optic nerve, adipose tissue, and extrinsic oculomotor muscles via light microscopy and immunohistochemistry.(AU)

RESUMO Objetivos: Identificar vasos linfáticos em espécimes orbitários de cadáveres humanos através de microscopia óptica e análise imunohistoquímica. Métodos: Um estudo postmortem incluiu dez espécimes orbitários provenientes de dez cadáveres humanos. Todos os espécimes orbitários foram obtidos até 12 horas após a morte com uma técnica cirúrgica de exenteração orbitária e dissecados em glândula lacrimal, nervo óptico, gordura órbitária e músculos extraoculares. Para classificar como um vaso linfático, os critérios histológicos incluíram vasos endoteliais de parede única sem membrana basal bem desenvolvida, irregulares e lúmen sem hemácias, e os critérios imunohistoquímicos incluíram vasos endoteliais de parede única, com formato irregular e lúmen sem hemácias e reagentes a podoplanina D2-40. Resultados: As lâminas histológicas de glândula lacrimal, nervo óptico, tecido adiposo e músculos extraoculares reagiram positivamente a podoplanina D2-40. Conclusão: Este estudo demonstrou vasos linfáticos na órbita humana, mais exatamente, na glândula lacrimal, no nervo óptico, na gordura orbitária e nos músculos extrínsecos extraoculares via microscopia óptica e imunohistoquímica.(AU)

Gross anatomy, histological, and histochemical analysis of the eyelids and orbital glands of the neonate pygmy hippopotamus (Suina: Choeropsis liberiensis or Hexaprotodon liberiensis, Morton 1849) with reference to its habitat.

The pygmy hippopotamus is phylogenetically related to members of both the Suidae and Cetacea. However, differences in their habitats may have resulted in variation in the anatomy and physiology of the ocular adnexa between these species. Therefore, this study focuses on the identification of accessory organs of the eye, which are typical for the pygmy hippopotamus and are comparable to organs present in mammals related to it. Moreover, the secretions produced by the superficial gland of the third eyelid, the deep gland of the third eyelid and the lacrimal gland were examined, as they ensure eyeball protection. In the upper and lower eyelids, numerous serous glands where identified, which were typical for the pygmy hippopotamus and similar as in the Cetacea. This study enabled to identify additional folds in the eyelids of the pygmy hippopotamus. Lymphoid follicles and diffuse lymphocytes were not found in the lymphoid region in the upper or lower eyelids and the third eyelid, which was most likely caused by the age of the studied hippopotamuses. An accurate histochemical analysis revealed that the secretions of the pygmy hippopotamus are very similar to the Sus scrofa. The structural differences between the pygmy hippopotamus and representatives of Cetacea are most likely caused by the fact that most of Cetacea live in saltwater and are exposed to more frequent fluctuations in water temperature compared to the pygmy hippopotamus, which lives in fresh water and does not lead a migratory lifestyle like the Cetacea.

Anatomic Danger Zones of the Head and Neck.

BACKGROUND: Dermatologic procedures require a detailed understanding of surface anatomy to avoid complications. The head and neck region has prominent danger zones including nerves and vasculature that may be at risk during cutaneous surgery. A thorough understanding of these danger zones can help avoid complications that may lead to functional or cosmetic impairment. METHODS: The anatomic literature regarding the course of high-risk structures of the head and neck was reviewed. Structures deemed at risk during dermatologic procedures were included in the analysis. The final analysis focused on branches of the facial nerve, parotid duct, spinal accessory nerve, trigeminal nerve, and the lacrimal system. Anatomical information was compiled regarding each high-risk structure to develop a "danger zone" at which each respective structure is at risk. RESULTS: The danger zone for each structure was compiled based on the review of the literature and depicted in the figures. CONCLUSION: With careful attention to anatomy and the meticulous surgical technique, there is great potential for reduction in surgical injury to danger zones of the head and neck.

The Human Lacrimal Gland: Historical Perspectives, Current Understanding, and Recent Advances.

PURPOSE: The lacrimal glands produce the aqueous component of the pre-ocular tear film, which is essential for ocular health and optimal vision. This review explores its history, current understanding, recent advances, and scope for future research. METHODS: The authors reviewed the major studies discussing the history of lacrimal glands and their anatomical description, including microscopic anatomy, innervation patterns, imaging, and ongoing translational research. RESULTS: The review traces the evolution of human knowledge about the source of tears across several millennia, with specific emphasis on the individuals who made seminal contributions to this field. It provides a detailed update on the morphology, microscopic structure, innervation, vascular supply, and imaging modalities of both the main and accessory lacrimal glands. The review also summarizes the recent advances in lacrimal gland regeneration and repair for the treatment of dry eye disease, particularly the role of mesenchymal stem cells. Lastly, the review gazes into the future of lacrimal gland research, which aims at translating the existing laboratory knowledge into clinical application, with the possibility of transplanting in vitro cultivated lacrimal constructs or the use of cell-based therapies for in situ repair of diseased human lacrimal glands. CONCLUSIONS: Knowledge about the lacrimal glands in health and disease has improved tremendously since its discovery in the mid-eighteenth century. Today we stand at the cusp of exploring potential regenerative approaches for the treatment of lacrimal gland damage in dry eye disease.

Adding myofibroblasts to the lacrimal pump.

The lacrimal sac (LS) empties in the nasolacrimal duct to drain the tears in the inferior nasal meatus. Different studies indicated the role of the lacrimal pump in the lacrimal drainage. Although controversial, the lacrimal pump mechanism is an extrinsic one, either active, or passive. An intrinsic contractile potential of the LS was not documented previously. We thus aimed a retrospective immunohistochemical study to test the alpha-smooth muscle actin (α-SMA) and h-caldesmon expression in the LS wall. We used archived paraffin-embedded samples of LS from ten adult patients. The α-SMA + phenotype was detected in basal epithelial cells, in subepithelial ribbons of stromal cells, in vascular smooth muscle cells, as well as in pericytes. H-caldesmon was exclusively expressed in pericytes, vascular smooth muscle cells and myoepithelial cells of the subepithelial glands. The most striking feature we found in all samples was a consistent stromal network of α-SMA+/h-caldesmon- myofibroblasts. This finding supports an intrinsic scaffold useful for the lacrimal pump.

Comparative study of the eyelids and orbital glands morphology in the okapi (Okapia johnstoni, Giraffidae), Père David's deer (Elaphurus davidianus, Cervidae) and the Philippine mouse-deer (Tragulus nigricans, Tragulidae).

The accessory organs of the eye represent part of the protective system of the eyeball. In the present study, an examination of the accessory organs of the eye of three species of captive ruminants was performed using light microscopy. In the okapi, the superficial gland of the third eyelid and lacrimal gland were complex branched multilobar tubular glands formed by mucous units with tubular secretory portions and no plasma cells. The deep gland of the third eyelid was absent in the okapi and present in both the Père David's deer and the Philippine mouse-deer. In the Philippine mouse-deer, the deep gland had a very thick connective capsule and thick interlobar septae. It contained fewer lobes forming the gland parenchyma compared to Père David's deer and other ruminants. Organized lymphoid follicles were present within the upper and lower eyelids only in the okapi and Père David's deer, while diffuse lymphocytes were observed in the Philippine mouse-deer. The orbital glands in the Père David's deer had a multilobar tubuloacinar structure with numerous plasma cells and a mucoserous character. In contrast to the Philippine mouse-deer, these glands had a serous character. The presence of several macroscopic and microscopic structural differences of the examined accessory organs of the eye in the three captive ruminant species may be understood within an ecological context and may be associated with different habitat-specific environmental conditions.

Anatomical variations of the levator palpebrae superioris, including observations on its innervation and intramuscular nerves' distribution pattern.

BACKGROUND: The levator palpebrae superioris muscle (LPS) acts as the upper eyelid's major elevator and retractor and is innervated by the oculomotor nerve. The muscle's paralysis is manifested by ptosis. MATERIAL AND METHODS: 70 orbits were dissected. After removing the orbital roof, the LPS' shape and anatomical variations (i.e., the presence of accessory muscular bands or atypical formation of the muscle) were assessed. To visualize the distribution of the oculomotor nerve's intramuscular sub-branches, the isolated levator palpebrae superioris muscles were stained using Sihler's staining technique. RESULTS: Several LPS anatomical variations were observed in the specimens examined, in seven of which (7/70; 10%) additional delicate muscular slips arose from the LPS' lateral border and reached the lacrimal gland. Histological examination confirmed the presence of striated skeletal muscle fibers in all those cases. In three other specimens (3/70; 4.28%), supernumerary muscular bands ("tensor trochleae") were found that linked the levator with the superior oblique muscle's trochlea. In the next case, the LPS' origin was double and the muscle was bipartite on its proximal half. In most cases (55/70; 78.6%), muscular branches formed a single bundle that wrapped around the superior rectus muscle's medial border to reach the levator's inferior surface. Intramuscular sub-branches were distributed largely within the proximal two-thirds of the LPS and formed an irregular, tree-like pattern. However, thin sub-branches and small retrograde sub-branches extended as far as the muscle's insertion. CONCLUSIONS: Plastic surgeons and ophthalmologists should be aware of the levator palpebrae superioris muscle's anatomic variations both in planning and conducting surgeries on the upper eyelid.

Positional relationship between medial canthal tendon and common canalicular orifice: A cadaveric study.

PURPOSE: To examine the positional relationship between the medial canthal tendon (MCT) and the common canalicular orifice (CCO) in cadavers. METHODS: This experimental anatomical study was conducted using 75 orbits from 48 embalmed Japanese cadavers fixed in 10% buffered formalin (24 orbits from 17 males and 51 orbits from 31 females; 38 right and 37 left; mean age at time of death, 84.1±9.2 years). The vertical width of the MCT on the level of the medial orbital rim and the angle between the MCT and axial plane were measured. In addition, the vertical distance from the CCO to the lower edge of the MCT was measured. Positive values of the distance were indicated when the CCO was located below the lower edge of the MCT. RESULTS: The vertical distance from the CCO to the lower edge of the MCT was -1.43±1.31mm. Only 13 orbits (17.3%) showed the CCO located on the same level (2 orbits, 2.7%) or below the lower edge of the MCT (11 orbits, 14.7%), while the CCO was located above the lower edge of the MCT in 62 orbits (82.7%). In multiple regression analyses, both the MCT width and angle between the MCT and axial plane were not correlated with the distance (P>0.050). CONCLUSIONS: As the CCO was mostly found to be located above the inferior margin of the MCT, the creation of the bony window up to the MCT's inferior margin is not sufficient in external dacryocystorhinostomy to completely expose the CCO.

Mohs Surgery for Periocular Tumors.

BACKGROUND: Skin cancers of the periorbital area present unique challenges to Mohs surgeons. OBJECTIVE: The need for precise and high-quality Mohs micrographic surgery (MMS) is paramount because of the complex anatomy, vital structures, and potential threat to vision. METHODS: A thorough comprehension of anatomy is essential to help predict tumor behavior and ensure successful outcomes for patients. RESULTS: Tumors occurring at the medial and lateral canthi are of greatest concern for deeper orbital penetration. CONCLUSION: In this study, we present our experience with MMS of periorbital tumors, including clinical pearls and techniques to aid the Mohs surgeon.

Transnasal prelacrimal approach to the inferior intraconal space: a feasibility study.

BACKGROUND: Endonasal access to the inferomedial and inferolateral intraconal space via the orbital floor has not been reported. The primary purpose of this study was to assess the feasibility of accessing the inferior intraconal space through the orbital floor via a transnasal prelacrimal approach. Secondarily, it aims to highlight anatomical relationships of neurovascular structures in this space, as a requirement to prevent complications. METHODS: Six cadaveric heads (12 sides) were dissected using a transnasal prelacrimal approach. The orbital floor, medial to the infraorbital canal, was removed and the periorbita opened to expose the inferior rectus muscle. The inferomedial and inferolateral intraconal space was accessed alongside the medial and lateral border of inferior rectus muscle, respectively. Various anatomical relationships of adjacent neurovascular structures were recorded, and the distances among the recti muscles and optic nerve were also measured. RESULTS: The infraorbital nerve is located at the inferolateral aspect of inferior rectus muscle. In the inferomedial intraconal space, we identified the inferomedial muscular trunk of the ophthalmic artery, optic nerve, and branches of the oculomotor nerve; whereas the inferolateral intraconal space contained the inferolateral muscular trunk of ophthalmic artery, branches of the oculomotor and nasociliary nerve, and abducens nerve. Distances from the medial, inferior, and lateral recti muscles to the optic nerve were (mean ± standard deviation) 4.70 ± 1.18 mm, 5.60 ± 0.93 mm, and 7.98 ± 1.99 mm, respectively. Distances from the inferior rectus muscle to the inferior borders of medial and lateral recti muscles were 4.45 ± 1.23 mm and 8.77 ± 1.80 mm. CONCLUSION: It is feasible to access the inferior intraconal space through the orbital floor via a transnasal prelacrimal approach. The access may be subdivided into inferomedial and inferolateral corridors according to the entry point at the medial or lateral border of the inferior rectus muscle. Neurovascular structures in the inferior intraconal space are visualized directly, which should enhance their preservation.

Punctal agenesis: Embryology, presentation, management modalities and outcomes.

Punctal agenesis is defined as the absence of the punctum occurring secondary to a failure of embryogenesis. This review synthesizes existing data on the embryology, anatomy, clinical presentation, symptomatology, management options and treatment outcomes of punctal agenesis. A foundational knowledge of the underlying embryologic and anatomical abnormalities is fundamental to understanding its clinical presentation and assists in choosing an appropriate management strategy. Existing outcomes data is generally favorable and suggests management with a step-wise approach can alleviate symptoms in patients across a spectrum of disease.

Anterior maxillary wall and lacrimal duct relationship in Orientals: CT analysis for prelacrimal access to the maxillary sinus.

BACKGROUND: The pre-lacrimal window approach (PLWA) is a promising technique in approaching lesions of the anterior wall and floor of the maxillary sinus. Simmen et al. previously reported that this approach is feasible in only 2/3 of their patients. This percentage appears to be lower than that of our local (mainly Chinese) population based on our clinical experience. Our study aims to measure the distance between the anterior maxillary wall and lacrimal duct in ethnic Chinese. A higher incidence of sphenoid-ethmoidal cells has been reported in Orientals. We postulate that there is also a higher incidence of wider pre-lacrimal recesses in Orientals thus making the PLWA more feasible to perform in Orientals. METHODS: 100 consecutive sinus CT scans of adult patients with various rhinologic diseases that did not distort the bony anatomy of the maxilla were reviewed (2 sides each). The distance between the anterior maxillary wall and the anterior border of the lacrimal duct was measured in 200 sides. We have adopted the methodology of measurements previously published by Simmen et al.  This is so that we could compare between Oriental and Occidental paranasal sinuses. RESULTS: A distance of more than 7 mm was found in 39.5% of our subjects and a distance of > 3-7 mm was seen in 53.5%. In 6.5% of our subjects we found a prelacrimal recess < 3 mm. CONCLUSION: The PLWA could have been performed without removal of the bony lacrimal canal in 39.5% of our subjects ( > 7 mm). Good access to the anterior maxilla wall could also have been possible for 53.5% with sub-periosteal removal of the bony lacrimal canal and medial maxillary wall. Thus, the PLWA would have been feasible for 93% of our subjects. These percentages are significantly higher than Simmen's study of 68.5% in an Occidental population.

A major review on disorders of the animal lacrimal drainage systems: Evolutionary perspectives and comparisons with humans.

PURPOSE: To provide a systematic review of the literature on the disorders and management of the lacrimal drainage system (LDS) in few of the species of the animal kingdom. METHODS: The authors performed a PubMed search of all articles that were published in English with specific reference to lacrimal drainage disorders in animals. Data captured include demographics, presentations, investigation, diagnoses and management modalities. Emphasis was also on anatomical differences, evolutionary perspectives and addressing the lacunae and potential directions for future research. RESULTS: The lacrimal drainage system is a terrestrial adaptation in vertebrates. Evolutionary development of the LDS is closely linked to the Harderian gland and the vomeronasal organ. Variable differences in the clinical presentations and management of lacrimal drainage disorders (LDD) are noted in comparison to humans. These are secondary to unique structural and pathophysiological differences. Uniformity in usage and reporting of disease terminologies is required. Diagnostic challenges in clinical examination can be met with the development of customized lacrimal instruments. Contrast dacryocystorhinography is a very useful investigation in the diagnosis of LDD. Multiple bypass procedures like conjunctivorhinostomy, conjunctivobuccostomy and conjunctivomaxillosinosotomy have been described for nasolacrimal duct obstruction (NLDO). Advances of endoscopy and radiological techniques are paralleled by minimally invasive lacrimal interventions. The search for an ideal animal model for human LDS is far from over and the choice of the animal needs to be customized based on the research objectives. CONCLUSION: The lacrimal drainage system is an ancestral feature in tetrapod vertebrates and it is present, in some form or another, in most descendant species. The lacrimal drainage system has evolved considerably, adapting to the needs of the species. It is essential to understand the lacrimal drainage disorders of domestic animals so that the animal and human lacrimal sciences contribute more meaningfully to each other.

Anatomical considerations in endoscopic lacrimal surgery.

PURPOSE: To provide a review of the anatomy of the lacrimal drainage system and lateral wall of the nose pertaining to endoscopic dacryocystorhinostomy. METHODS: The authors performed a PubMed search of articles published pertaining to the anatomy of the lateral wall of the nose and the anatomy of endonasal and external dacryocystorhinostomy surgery. RESULTS: The article covers the regional surface and surgical anatomy for endoscopic dacryocystorhinostomy (DCR), including the maxillary line, middle turbinate, agger nasi air cell, lacrimal sac and fossa and the upper portion of the nasolacrimal drainage system. It also explores the dimensions and location of bony ostium formation to ensure full exposure and marsupialisation of the lacrimal sac. Finally, it covers the anatomy of potential complications of endoscopic DCR surgery including penetration of the skull base and orbit, inadvertent entry to the maxillary sinus and breach of the skin. CONCLUSION: A good understanding of the anatomy of the lacrimal drainage system and the lateral wall of the nose will increase the likelihood of successful surgery and minimize the risk of complications and damage to neighbouring structures such as the orbit and skull base.