Accessory Muscles Associated With the Levator Palpebrae Superioris Muscle in 100 Cadavers.

PURPOSE: This study aimed to determine the variations of the levator palpebrae superioris muscle and to reveal its morphological features. METHODS: This study conducted on 100 adult orbit cadavers in the Department of Anatomy, Istanbul University, used an exploratory, descriptive research design. The anatomical and morphological variations of the levator palpebrae superioris muscle and its relationship with the superior ophthalmic vein were evaluated. RESULTS: Variations of levator palpebrae superioris muscle were discovered in 11 of 100 orbits. Single (9%), double (1%), and triple (1%) accessory muscle slips were observed. The origin of accessory muscle slips showed variation as the accessory muscle slips originated either from the proximal or distal half of the levator palpebrae superioris muscle. Also, the insertions of accessory muscle slips were variable, as they were inserted into levator aponeurosis, trochlea, lacrimal gland, lateral orbital wall, or the fascia of the superior ophthalmic vein. CONCLUSIONS: Accessory muscles associated with levator aponeurosis were found in a significant proportion of cadavers. These muscles may cause confusion in orbital surgery and should be taken into account during surgical planning and orientation in the superior orbit.

Orbital structures in the pediatric age group: A normative assessment using magnetic resonance imaging.

PURPOSE: Many diseases of traumatic, infectious, endocrinologic and neoplastic origin can lead to orbital involvement and related morphological changes. In the present study, we aimed to determine the age-based normal orbital measurements using magnetic resonance imaging (MRI) in pediatric patients. METHODS: Our retrospective study included 186 patients with normal orbital MRI findings. The patients were divided into the following five groups based on their age. Group 1: 1-24 months; Group 2: 25-60 months; Group 3: 61-120 months; Group 4: 121-168 months; and Group 5: 169-216 months. Globe position relative to interzygomatic line (IZL) and orbital rim, optic nerve-sheath complex, extraocular muscle diameters, were measured. RESULTS: The differences among the age groups for the distances between cornea and sclera in relation to IZL, for the distances between cornea and sclera relative to orbital rim, and for the extraocular muscle diameters were statistically significant. In terms of the extraocular muscle diameter, it was found that the thinnest muscle of all groups was the lateral rectus muscle while the thickest was the medial rectus muscle. CONCLUSION: In pediatric patients who were divided into five groups based on their age, the positions of bulbus oculi relative to IZL or orbital rim and the normal diameter ranges of extraocular muscles and of the optic nerve-sheath complex in orbital MRI were determined. We are of the opinion that the presence of such a scale could be a guide in the evaluation of orbital MRI in pediatric patients.

Topographical anatomy of the annulus of Zinn.

The anatomy and even existence of a common tendinous origin of the extraocular eye muscles, or annulus of Zinn, has widely been debated in anatomical literature. This study explored the anatomical origins of the recti muscles, their course into the orbit and the dural connections of the common tendinous origin with the skull base. Twenty orbits of ten adult human cadavers were dissected. The orbital apex and its dural connections were photographed. Histological examination of apical specimens was performed. In all cadavers, extraocular muscles were observed to have a common tendinous origin at the orbital apex, continuous with dural connections extending into the skull base. Accessory slips of the medial rectus were observed across all cadavers. Dual heads of the lateral rectus were observed in fourteen orbits of seven cadavers. The origin of the levator palpebrae superioris appeared to be contiguous with the superior rectus at the common tendinous origin in all but one cadaver. These results support the existence of a common tendinous origin of the extraocular muscles, that is continuous with the skull base dura. In addition, they support the existence of variations in orbital anatomy including dual or accessory muscle slips of the extraocular muscles.

"Hammock" suspending the superior ophthalmic vein: a magnetic resonance imaging study.

PURPOSE: The present study aimed to explore the hammock-like structure suspending the superior ophthalmic vein (SOV) using magnetic resonance imaging (MRI). METHODS: Following conventional MRI examination, 93 outpatients underwent thin-sliced, coronal T2-weighted and contrast imaging of the orbit. RESULTS: SOVs were consistently detected in all 93 patients. In 90.3% of patients, a hammock-like structure suspending the SOV was identified, which was present on both sides in 64.5% of patients. The structure was frequently located in the anterior and middle thirds of the retrobulbar orbit, suspended from the superolateral corner of the orbital walls. The medial edge of the hammocks did not reach the orbital walls; therefore, they partially encased the SOV. The morphology of the hammock was highly variable between patients, although none were tethered to the extraocular muscles. In addition, a septal band connecting the hammock and optic sheath was identified in 36.6% of patients, most frequently located in the posterior third of the retrobulbar orbit. CONCLUSIONS: The hammock suspending the SOV and the septal band connecting the hammock and optic sheath may be structures that loosely anchor the SOV to the orbital fat to maintain a constant SOV flow, in addition to preventing excessive bends and obstructions.

Anatomical connections between the inferior fibers of the musculus orbicularis oculi and musculus levator labii superioris alaeque nasi / Conexiones anatómicas entre las fibras inferiores del músculo orbicular del ojo y levantador nasolabial

SUMMARY: This study aimed to determine the anatomical connections between the inferior fibers of M. orbicularis oculi (OOc inf.) and the M. levator labii superioris alaeque nasi (LLSAN), providing anatomical variations of the connecting fibers. This study examined the OOc and LLSAN of 44 specimens from 22 embalmed adult Korean cadavers. Connecting fibers between the OOc inf. and LLSAN were observed in 29.5 % of the specimens. Connecting patterns of the OOc inf. to the LLSAN were classified into three categories according to the directions of the connecting fibers; Type I (13.6 %), in which some of the OOc inf. coursed medially to blend with the lateral originating fibers of the LLSAN. Type II (11.4 %), in which some of the OOc inf. descended vertically to blend with the LLSAN. Type III (4.5 %), in which both types I and II were found simultaneously. Some of the OOc inf. coursed medially to blend with the lateral originating fibers of the LLSAN, and some of the OOc inf. descended vertically to blend with the LLSAN. These findings provide greater knowledge of the connecting fibers between the OOc inf. and LLSAN, thereby helping us understand complicated expressions, inject BoNT-A into related wrinkles, and analyze EMG activities.

RESUMEN: Este estudio tuvo como objetivo determinar las conexiones anatómicas entre las fibras inferiores del músculo orbicular del ojo (MOO inf.) y el levantador nasolabial (Musculus levator nasiolabialis; M. levator labii superioris alaeque nasi) (LNL), proporcionando variaciones anatómicas de las fibras conectoras. Se examinó el orbicularis oculi (MOO) y LNL de 44 especímenes de 22 cadáveres coreanos adultos embalsamados. Se observaron fibras conectoras entre los MOO inf. y LNL en el 29,5 % de los especímenes. Patrones de conexión del OOc inf. a LNL se clasificaron en tres categorías según las direcciones de las fibras conectoras; Tipo I (13,6 %), en el que algunos de los MOO inf. cursaban medialmente para mezclarse con las fibras de origen lateral del LNL. Tipo II (11,4 %), en el que algunos de los MOO inf. descendían verticalmente para mezclarse con el LNL. Tipo III (4,5 %), en el que se encontraron simultáneamente los tipos I y II. Algunos de los MOO inf. cursaron medialmente para mezclarse con las fibras de origen lateral de la LNL y algunas de las MOO inf. descendían verticalmente para mezclarse con el LNL. Estos hallazgos aportan un mayor conocimiento de las fibras conectoras entre los MOO inf. y LNL, lo que nos ayuda a comprender expresiones complicadas, inyectar BoNT-A en las arrugas relacionadas y analizar las actividades de EMG.

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)

Stereological quantification of extraocular muscles in humans / Cuantificación estereológica de músculos extraoculares en humanos

SUMMARY: The aim of this study is to quantify muscular and connective tissue volumes of extraocular muscles (EOM) in humans with no ophthalmological disease using stereology. EOM from five cadaveric non-strabismic humans were obtained. The number of muscle fibers in 5,000 µm2 and volume density (Vv) of muscle and collagen were measured using stereology. Comparisons between antagonist EOM were conducted using Wilcoxon signed rank test for paired samples. A secondary analysis examining differences between pairs of EOM was also conducted. Bilateral tests were performed, and significance was set at 0.05. The horizontal rectus muscles (medial and lateral rectus) had the highest Vv of muscle and the lowest Vv of collagen. The inferior rectus muscle tended to have a fewer number of fibers per 5,000 µm2 than the rest of the EOM. However, these differences did not reach statistical significance. This is the first published study describing the normal histology of human EOM using stereology. Our investigation, through the quantification of the proportion of muscle and collagen tissue, as well as the number of muscle fibers in 5,000 µ2, establishes normal stereological parameters for EOM of humans without ophthalmological disease.

RESUMEN: El objetivo de este estudio es cuantificar el volumen de tejido muscular y conectivo de los músculos extraoculares en humanos sin enfermedad oftalmológica conocida utilizando estereología. Los músculos extraoculares fueron obtenidos de cinco cadáveres humanos sin estrabismo. El número de fibras musculares en 5.000 µm2 y la densidad de volumen (Vv) de músculo y colágeno fueron medidas usando estereología. Las comparaciones entre músculos extraoculares antagonistas se realizaron a través de la prueba de los rangos con signo de Wilcoxon para muestras pareadas. Un análisis secundario examinando diferencias entre pares de músculos extraoculares también fue llevado a cabo. Se realizaron pruebas bilaterales y la significancia fue fijada en 0,05. Los músculos rectos horizontales (recto medial y lateral) tuvieron el mayor Vv de músculo y el menor Vv de colágeno. El músculo recto inferior tuvo la tendencia a poseer menos número de fibras por 5.000 µm2 que el resto de los músculos extraoculares. No obstante, estas diferencias no llegaron a ser estadísticamente significativas. Este es el primer estudio publicado describiendo la histología normal de los músculos extraoculares usando estereología. Nuestra investigación, a través de la cuantificación de la proporción de tejido de músculo y colágeno, así como el número de fibras musculares en µm2, establece parámetros estereológicos normales para músculos extraoculares en humanos sin enfermedad oftalmológica.

The oblique extraocular muscles in cetaceans: Overall architecture and accessory insertions.

The oblique extraocular muscles (EOMs) were dissected in 19 cetacean species and 10 non-cetacean mammalian species. Both superior oblique (SO) and inferior oblique (IO) muscles in cetaceans are well developed in comparison to out-groups and have unique anatomical features likely related to cetacean orbital configurations, swimming mechanics, and visual behaviors. Cetacean oblique muscles originate at skeletal locations typical for mammals: SO, from a common tendinous cone surrounding the optic nerve and from the medially adjacent bone surface at the orbital apex; IO, from the maxilla adjacent to lacrimal and frontal bones. However, because of the unusual orbital geometry in cetaceans, the paths and relations of SO and IO running toward their insertions onto the temporal ocular sclera are more elaborate than in humans and most other mammals. The proximal part of the SO extends from its origin at the apex along the dorsomedial aspect of the orbital contents to a strong fascial connection proximal to the preorbital process of the frontal bone, likely the cetacean homolog of the typical mammalian trochlea. However, the SO does not turn at this connection but continues onward, still a fleshy cylinder, until turning sharply as it passes through the external circular muscle (ECM) and parts of the palpebral belly of the superior rectus muscle. Upon departing this "functional trochlea" the SO forms a primary scleral insertion and multiple accessory insertions (AIs) onto adjacent EOM tendons and fascial structures. The primary SO scleral insertions are broad and muscular in most cetacean species examined, while in the mysticete minke whale (Balaenoptera acutorostrata) and fin whale (Balaenoptera physalus) the muscular SO bellies transition into broad fibrous tendons of insertion. The IO in cetaceans originates from an elongated fleshy attachment oriented laterally on the maxilla and continues laterally as a tubular belly before turning caudally at a sharp bend where it is constrained by the ECM and parts of the inferior rectus which form a functional trochlea as with the SO. The IO continues to a fleshy primary insertion on the temporal sclera but, as with SO, also has multiple AIs onto adjacent rectus tendons and connective tissue. The multiple IO insertions were particularly well developed in pygmy sperm whale (Kogia breviceps), minke whale and fin whale. AIs of both SO and IO muscles onto multiple structures as seen in cetaceans have been described in humans and domesticated mammals. The AIs of oblique EOMs seen in all these groups, as well as the unique "functional trochleae" of cetacean SO and IO seem likely to function in constraining the lines of action at the primary scleral insertions of the oblique muscles. The gimble-like sling formed by SO and IO in cetaceans suggest that the "primary" actions of the cetacean oblique EOMs are not only to produce ocular counter-rotations during up-down pitch movements of the head during swimming but also to rotate the plane containing the functional origins of the rectus muscles during other gaze changes.

Upper Eyelid Ptosis Correction with Levator Advancement in Asian Patients using the Musculoaponeurotic Junction of the Levator as the Key Reference Point.

Upper eyelid ptosis correction is a complex procedure. The ethnic differences in the Asian upper eyelid anatomy are compounded by the technical challenges of primary and revision ptosis correction. The authors present a technique of upper eyelid ptosis correction that estimates the exact location of suture fixation that uses the musculoaponeurotic junction of the levator as the reference point. The preoperative considerations in determining the fixation point relative to the musculoaponeurotic junction include the following: A, the extent of ptosis correction needed; B, the degree of compensatory brow elevation with eye opening; and C, eye dominance. The benefits of this approach are the shortened operative time because of more precise preoperative planning and greater predictability and reproducibility of the results. The authors have found that this technique produced consistent and superior results for ptosis correction in Asian patients.

Estudio de correlación en las medidas de ducciones pasivas oblicuas y de ciclorrotación / Correlation study in the measurements of oblique passive ductions and cyclorotation

OBJETIVO: Evaluar la repetibilidad intraobservador e interobservador de la «prueba de ducción forzada exagerada» o «prueba de tracción oblicua» y la «prueba de exciclo e inciclorrotación pasiva» o «prueba de tracción de ciclorrotación». MATERIALES Y MÉTODOS: Se estudiaron 44 ojos de 22 pacientes. Fueron evaluados bajo anestesia general profunda. La ducción pasiva se probó en supraducción e infraducción mediante la «prueba de ducción exagerada». La limitación en el movimiento se graduó de 0 a -4. La prueba de ciclorrotación pasiva se evaluó con retropulsión del globo hasta que se observa la primera resistencia. Utilizamos el anillo de Méndez y los puntos azules marcados en el limbo para medir la cantidad de ciclorrotación. Se registraron los resultados obtenidos de exciclo e inciclorrotación. Todas las mediciones se realizaron por duplicado para cada uno de los 2 observadores. RESULTADOS: El coeficiente de correlación intraclase de la «prueba de tracción oblicua» entre los 2 observadores para el oblicuo inferior fue 0,738 (intervalo de confianza del 95%, 0,62-0,83) y 0,910 para el oblicuo superior (intervalo de confianza del 95%, 0,85-0,94). El coeficiente de correlación intraclase de «prueba de tracción de ciclorrotación» de los 2 observadores fue de 0,827 (intervalo de confianza del 95%, 0,74-0,89) para excicloducción y 0,792 (intervalo de confianza del 95%, 0,67-0,85) para incicloducción. El porcentaje de pacientes dentro de 5̊ de rotación interobservador fue de 84,1% para exciclo y 81,8% para inciclorrotación. Ambas pruebas tuvieron una mejor correlación intraobservador que en la evaluación interobservador. CONCLUSIONES: La evaluación de «prueba de tracción oblicua» y «prueba de tracción de ciclorrotación» tuvo una correlación de moderada a buena entre los 2 observadores y buena a excelente en la evaluación intraobservador

PURPOSE: To evaluate intraoserver and inteobserver repeatability of the "exaggerated forced duction test" or "oblique traction test" and the "excyclo and incyclo passive rotation test" or "cyclorotation traction test". METHODS: 44 eyes of 22 patients were evaluated under deep general anesthesia. Passive duction was tested on supraduction and infraduction by the "exaggerated duction test". The limitation on movement was graduated from 0 to - 4. Passive cyclorotation test was evaluated with retropulsion of the globe until the first resistance is noted. We used the Mendez ring and blue dots marked on the limbus to measure the amount of cyclorotation. The results obtained of excyclo and incyclorotation were recorded. All measurements were made in duplicate for each of the two observers. RESULTS: The intraclass correlation of the "oblique traction test" coefficient between the two observers was for the IO was 0,738 (95% confidence interval, 0,62-0,83) and 0,910 for the superior oblique (SO) (95% confidence interval, 0,85-0,94). The "cyclorotation traction test" intraclass correlation coefficient of the between the two observers was 0,827 (95% confidence interval, 0,74-0,89) for exclycloduction and 0,792 (95% confidence interval, 0,67-0,85) for inclycloduction. The percentage of patients within 5° of rotation interobserver was 84,1% for excyclorotation and 81,8% for inclyclorotation. Both tests had better correlation on the intraobserver than interobserver evaluation. CONCLUSIONS: Evaluation of the "oblique traction test" and "cyclorotation traction test" had moderate to good correlation between the two observers and good to excellent on the intraobserver evaluation

Comparison of the Superior and Inferior Rectus Muscles in Humans: An Anatomical Study with Notes on Morphology, Anatomical Variations, and Intramuscular Innervation Patterns.

A comparison of the superior and inferior rectus muscles was performed to determine whether they have similar structures and innervation attributable to their participation in the same type of, although antagonistic, eye movements. The study was conducted on 70 cadaveric hemiheads, and the anatomical variations in the superior and inferior rectus muscles were assessed. Sihler's whole mount nerve staining technique was used on 20 isolated superior and 20 isolated inferior rectus muscle specimens to visualize the intramuscular distribution of the oculomotor nerve subbranches. In two cases (~2.8%), variant muscular slips were found that connected the superior and inferior rectus muscles. In 80% of cases, muscular branches arising directly from the inferior branch of the oculomotor nerve innervated the inferior rectus muscle, while in 20% of cases, the nerve to the inferior oblique muscle pierced the inferior rectus muscle and provided its innervation. In 15 of 70 specimens (21.4%), a branch to the levator palpebrae superioris muscle pierced the superior rectus muscle. The distance between the specific rectus muscle's insertion and the anterior-most terminations of the nerves' subbranches with reference to the muscle's total length ranged from 26.9% to 47.2% for the inferior rectus and from 34.8% to 46.6% for the superior rectus, respectively. The superior rectus muscle is slightly longer and its insertion is farther from the limbus of the cornea than is the inferior rectus muscle. Both muscles share a common general pattern of intramuscular nerve subbranches' arborization, with characteristic Y-shaped ramifications that form the terminal nerve plexus located near half of the muscles' length. Unexpected anatomical variations of the extraocular muscles may be relevant during orbital imaging or surgical procedures.

Haplotype-Based Genome-Wide Association Study and Identification of Candidate Genes Associated with Carcass Traits in Hanwoo Cattle.

Hanwoo, is the most popular native beef cattle in South Korea. Due to its extensive popularity, research is ongoing to enhance its carcass quality and marbling traits. In this study we conducted a haplotype-based genome-wide association study (GWAS) by constructing haplotype blocks by three methods: number of single nucleotide polymorphisms (SNPs) in a haplotype block (nsnp), length of genomic region in kb (Len) and linkage disequilibrium (LD). Significant haplotype blocks and genes associated with them were identified for carcass traits such as BFT (back fat thickness), EMA (eye Muscle area), CWT (carcass weight) and MS (marbling score). Gene-set enrichment analysis and functional annotation of genes in the significantly-associated loci revealed candidate genes, including PLCB1 and PLCB4 present on BTA13, coding for phospholipases, which might be important candidates for increasing fat deposition due to their role in lipid metabolism and adipogenesis. CEL (carboxyl ester lipase), a bile-salt activated lipase, responsible for lipid catabolic process was also identified within the significantly-associated haplotype block on BTA11. The results were validated in a different Hanwoo population. The genes and pathways identified in this study may serve as good candidates for improving carcass traits in Hanwoo cattle.

Anatomical variations and innervation patterns of the superior oblique muscle.

GOAL: The location and anatomical relationships of the superior oblique muscle make surgical intervention difficult. The aim of the present paper was therefore to supplement existing anatomical descriptions of this muscle. Its anatomical variability is particularly emphasized, including variations in muscle and tendon size and details of the innervation pattern. MATERIALS AND METHODS: The study was conducted on 78 orbits from 39 adult human cadavers of both sexes (18 males and 21 females). The roof and upper part of the medial and lateral walls of the orbit were carefully removed, which allowed the superior oblique muscle and trochlear nerve to be exposed along their entire course. Sihler's stain was applied to visualize the intramuscular distribution of the trochlear nerve. RESULTS: The length of the muscle between the origin and trochlea ranged from 37.8 to 56.5mm, the length of the tendinous expansion ranged from 16.3 to 22.8mm, and the width of the scleral insertion of the muscle's tendon ranged from 5.4 to 9.6mm. In two cadavers, accessory muscular slips connecting the levator palpebrae superioris muscle to the trochlea of the superior oblique muscle were present unilaterally. The distance from the level of the trochlea attachment to the anteriormost endings of the intramuscular branches varied from 17.2 to 21.5mm. CONCLUSIONS: The intramuscular nervous branches of the trochlear nerve form a tree-like pattern. Unexpected anatomical variations such as accessory muscular bands could be relevant during orbital imaging or surgeries.

A New Anatomy Finding of Levator Aponeurosis and Müller Muscle at Pretarsal Plate in Asian Males.

PURPOSE: To examine the fine anatomic structures between levator aponeurosis and Müller muscle in front of the tarsus. MATERIALS AND METHODS: Postmortem specimens of 6 Chinese males (5 elderly men, aging from 68 to 86 years; 1 child, 10 years old) were used. A 3-µm thickness sagittal section of the central part of the upper eyelid was prepared, and the samples were examined microscopically by using hematoxylin-eosin, Masson trichrome, and anti-smooth muscle actin antibodies staining. RESULTS: There are 2 new findings in this study, one is the posterior layer of the levator aponeurosis and the other is the extensions of Müller muscle. The posterior levator aponeurosis had different insertion patterns that approximately paralleled the extension line of the levator aponeurosis at the confluence of attachment site of the orbital septum on the levator superioris. Below the confluence, it took the form of a layered insertion, and then extended to the orbicularis oculi muscle and subcutaneous tissue rather than inserting directly into tarsus. The Müller muscle was a multilayered structure at the upper border of tarsus. The superior Müller muscle extended above the peripheral arcade, and the inferior Müller muscle tendon was attached to the surface of tarsus with an Umbrella-shaped fiber. CONCLUSIONS: The authors discovered that the levator aponeurosis had different insertion patterns of the posterior layers. The Müller muscle gave branches at the peripheral arcade: the anterior one crossed the peripheral arcade and extended to the tarsus, and the posterior one attached and extended to the tarsus.

Cetacean Orbital Muscles: Anatomy and Function of the Circular Layers.

Dissections of cetacean orbits identified two distinct circular muscle layers that are uniquely more elaborate than the orbitalis muscles described in numerous mammals. The circular orbital muscles in cetaceans form layers that lie both external and internal to the rectus extra ocular muscles (EOMs). A cone-shaped external circular muscle (ECM) that invests the external surface of the rectus EOMs was found in all cetacean specimens examined. The cetacean ECM corresponds generally to descriptions of the musculus orbitalis in various mammals but is more strongly developed and has more layers than in noncetaceans. A newly identified internal circular muscle (ICM) is located internal to the rectus EOMs and external to the retractor bulbi (RB). The RB is massive in cetaceans and is encased in a connective tissue layer containing convoluted bundles of blood vessels. The most robust ECM and ICM layers were in sperm whale (Physeter macrocephalus) where they form complete rings. Surprisingly, histological analysis showed the sperm whale ECM to contain both smooth and striated (skeletal) muscle layers while the ICM appeared to contain solely skeletal muscle fibers. The extreme development of the ECM (orbitalis) and RB suggest a co-evolved system mediating high degrees of protrusion and retraction in cetaceans. We know of no homolog of the ICM but its function seems likely related to the complex vascular structures surrounding and deep to the retractor muscle. Skeletal muscle components in orbital circular muscles appear to be highly derived specializations unknown outside of cetaceans. Anat Rec, 2019. © 2019 American Association for Anatomy Anat Rec, 303:1792-1811, 2020. © 2019 American Association for Anatomy.

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.

Regional Anesthesia for Pediatric Ophthalmic Surgery: A Review of the Literature.

Ophthalmic pediatric regional anesthesia has been widely described, but infrequently used. This review summarizes the available evidence supporting the use of conduction anesthesia in pediatric ophthalmic surgery. Key anatomic differences in axial length, intraocular pressure, and available orbital space between young children and adults impact conduct of ophthalmic regional anesthesia. The eye is near adult size at birth and completes its growth rapidly while the orbit does not. This results in significantly diminished extraocular orbital volumes for local anesthetic deposition. Needle-based blocks are categorized by relation of the needle to the extraocular muscle cone (ie, intraconal or extraconal) and in the cannula-based block, by description of the potential space deep to the Tenon capsule. In children, blocks are placed after induction of anesthesia by a pediatric anesthesiologist or ophthalmologist, via anatomic landmarks or under ultrasonography. Ocular conduction anesthesia confers several advantages for eye surgery including analgesia, akinesia, ablation of the oculocardiac reflex, and reduction of postoperative nausea and vomiting. Short (16 mm), blunt-tip needles are preferred because of altered globe-to-orbit ratios in children. Soft-tip cannulae of varying length have been demonstrated as safe in sub-Tenon blockade. Ultrasound technology facilitates direct, real-time visualization of needle position and local anesthetic spread and reduces inadvertent intraconal needle placement. The developing eye is vulnerable to thermal and mechanical insults, so ocular-rated transducers are mandated. The adjuvant hyaluronidase improves ocular akinesia, decreases local anesthetic dosage requirements, and improves initial block success; meanwhile, dexmedetomidine increases local anesthetic potency and prolongs duration of analgesia without an increase in adverse events. Intraconal blockade is a relative contraindication in neonates and infants, retinoblastoma surgery, and in the presence of posterior staphylomas and buphthalmos. Specific considerations include pertinent pediatric ophthalmologic topics, block placement in the syndromic child, and potential adverse effects associated with each technique. Recommendations based on our experience at a busy academic ophthalmologic tertiary referral center are provided.

Location of the myoneural junction of the inferior oblique muscle: An anatomic study.

PURPOSE: To examine both the horizontal and vertical locations of the myoneural junction of the inferior oblique muscle (IOM) in reference to the ala nasi, IOM origin, and inferior orbital rim. MATERIALS AND METHODS: Fifty-six orbits from 56 Japanese cadavers (15 male and 41 female cadavers; average age at time of death, 86.5±9.4 years) were used in this experimental anatomical study. The inter-alae-nasi distance and the horizontal distances from the ipsilateral ala nasi to the IOM origin (ala-nasi-origin distance) and to the myoneural junction (ala-nasi-junction distance) were measured. The horizontal distance from the IOM origin to the myoneural junction (origin-junction distance) was calculated by subtraction of the ala-nasi-origin distance from the ala-nasi-junction distance. The vertical distance from the inferior orbital rim to the myoneural junction (rim-junction distance) was also measured. RESULTS: The ala-nasi-junction, origin-junction, and rim-junction distances were 12.2±3.2mm, 10.6±3.2mm, and 3.4±1.0mm, respectively. Males had a longer inter-alae-nasi distance than females (P<0.001), although the other distances did not show statistically significant sex-related difference (P>0.050). The ala-nasi-junction distance tended to be negatively correlated with the inter-alae-nasi distance (r=-0.222, P=0.050). CONCLUSIONS: The ala-nasi-junction distance can be affected by the inter-alae-nasi distance, which was found to be longer in males. Therefore, the IOM origin and the inferior orbital rim can be considered as more practical and reliable reference points to predict the location of the myoneural junction during the posterior inferior orbitotomy, irrespective of sex.

T2 mapping of the extraocular muscles in healthy volunteers: preliminary research on scan-rescan and observer-observer reproducibility.

BACKGROUND: T2-mapping technique and derived T2 relaxation time allows quantitative assessment of extraocular muscles; however, the reproducibility of T2 mapping-derived parameters was seldom studied till now. PURPOSE: To evaluate the scan-rescan and observer-observer reproducibility of T2 relaxation time measurements of extraocular muscles in young healthy volunteers. MATERIAL AND METHODS: Fourteen volunteers underwent T2-mapping examinations of the extraocular muscles three times within one month on a 3.0-T MR system. Scan-rescan and observer-observer reproducibility of T2 relaxation time measurements of the extraocular muscles were assessed using intraclass correlation coefficient and coefficient of variation. RESULTS: Both scan-rescan (short-term and long-term) and observer-observer could achieve good to excellent reproducibility, while better short-term than long-term scan-rescan reproducibility was obtained. The coefficient of variation of the T2 relaxation time of each extraocular muscles during both scan-rescan and observer-observer reproducibility assessment were <6%. CONCLUSION: T2 relaxation time measurement of the extraocular muscles is proven to be highly reproducible at 3.0 T. T2 mapping may be a potential imaging technique in the diagnosis and follow-up of orbital diseases involved extraocular muscles in further studies.

An accurate interactive segmentation and volume calculation of orbital soft tissue for orbital reconstruction after enucleation.

BACKGROUND: Accurate measurement and reconstruction of orbital soft tissue is important to diagnosis and treatment of orbital diseases. This study applied an interactive graph cut method to orbital soft tissue precise segmentation and calculation in computerized tomography (CT) images, and to estimate its application in orbital reconstruction. METHODS: The interactive graph cut method was introduced to segment extraocular muscle and intraorbital fat in CT images. Intra- and inter-observer variability of tissue volume measured by graph cut segmentation was validated. Accuracy and reliability of the method was accessed by comparing with manual delineation and commercial medical image software. Intraorbital structure of 10 patients after enucleation surgery was reconstructed based on graph cut segmentation and soft tissue volume were compared within two different surgical techniques. RESULTS: Both muscle and fat tissue segmentation results of graph cut method showed good consistency with ground truth in phantom data. There were no significant differences in muscle calculations between observers or segmental methods (p > 0.05). Graph cut results of fat tissue had coincidental variable trend with ground truth which could identify 0.1cm3 variation. The mean performance time of graph cut segmentation was significantly shorter than manual delineation and commercial software (p < 0.001). Jaccard similarity and Dice coefficient of graph cut method were 0.767 ± 0.045 and 0.836 ± 0.032 for human normal extraocular muscle segmentation. The measurements of fat tissue were significantly better in graph cut than those in commercial software (p < 0.05). Orbital soft tissue volume was decreased in post-enucleation orbit than that in normal orbit (p < 0.05). CONCLUSION: The graph cut method was validated to have good accuracy, reliability and efficiency in orbit soft tissue segmentation. It could discern minor volume changes of soft tissue. The interactive segmenting technique would be a valuable tool for dynamic analysis and prediction of therapeutic effect and orbital reconstruction.