Bilaminar Structure of the Human Optic Nerve Sheath.

Purpose/aim: We aimed to characterize the connective tissue microanatomy, elastin abundance, and fiber orientation in the human optic nerve sheath, also known as the optic nerve dura mater, for correlation with its biomechanical properties.

Materials And Methods: Seven whole human orbits aged 4-93 years, and five isolated human optic nerve sheaths aged 26-75 years were formalin fixed, paraffin embedded, coronally sectioned, stained by Masson trichrome and van Gieson's elastin methods, and analyzed quantitatively for elastin fiber abundance and orientation. Elastin area fraction was defined as area stained for elastin divided by total area.

Bilaminar Mechanics of the Human Optic Nerve Sheath.

Purpose/aim: The adult human optic nerve (ON) sheath has recently been recognized to be bilaminar, consisting of inner layer (IL) and outer layer (OL). Since the ON and sheath exert tension on the globe in large angle adduction as these structures transmit reaction force of the medial rectus muscle to the globe, this study investigated the laminar biomechanics of the human ON sheath.

Materials And Methods: Biomechanical characterization was performed in ON sheath specimens from 12 pairs of fresh, post-mortem adult eyes.

Compartmental Innervation of the Superior Oblique Muscle in Mammals.

Purpose: Intramuscular innervation of mammalian horizontal rectus extraocular muscles (EOMs) is compartmental. We sought evidence of similar compartmental innervation of the superior oblique (SO) muscle.

Methods: Three fresh bovine orbits and one human orbit were dissected to trace continuity of SO muscle and tendon fibers to the scleral insertions.

Nonclassical innervation patterns in mammalian extraocular muscles.

Purpose: The abducens (CN6) and oculomotor (CN3) nerves (nn) enter target extraocular muscles (EOMs) via their global surfaces; the trochlear (CN4) nerve enters the superior oblique (SO) muscle on its orbital surface. Motor nn are classically described as entering the EOMs in their middle thirds. We investigated EOM innervation that does not follow the classic pattern.

Characterization of ocular tissues using microindentation and hertzian viscoelastic models.

Purpose: The authors applied a novel microindentation technique to characterize biomechanical properties of small ocular and orbital tissue specimens using the hertzian viscoelastic formulation, which defines material viscoelasticity in terms of the contact pressure required to maintain deformation by a harder body.

Methods: They used a hard spherical indenter having 100 nm displacement and 100 μg force precision to impose small deformations on fresh bovine sclera, iris, crystalline lens, kidney fat, orbital pulley tissue, and orbital fatty tissue; normal human orbital fat, eyelid fat, and dermal fat; and orbital fat associated with thyroid eye disease. For each tissue, stress relaxation testing was performed using a range of ramp displacements.

Intramuscular innervation of primate extraocular muscles: unique compartmentalization in horizontal recti.

Purpose: It has been proposed that the lateral rectus (LR), like many skeletal and craniofacial muscles, comprises multiple neuromuscular compartments subserving different physiological functions. To explore the anatomic potential of compartmentalization in all four rectus extraocular muscles (EOMs), evidence was sought of possible regional selectivity in intramuscular innervation of all rectus EOMs.

Methods: Whole orbits of two humans and one macaque monkey were serially sectioned at 10 μm thickness and stained with Masson's trichrome.

Compartmentalized innervation of primate lateral rectus muscle.

Purpose: Skeletal and craniofacial muscles are frequently composed of multiple neuromuscular compartments that serve different physiological functions. Evidence of possible regional selectivity in LR intramuscular innervation was sought in a study of the anatomic potential of lateral rectus (LR) muscle compartmentalization.

Methods: Whole orbits of two humans and five macaque monkeys were serially sectioned at 10-microm thickness and stained with Masson trichrome.

Effects of intracranial trochlear neurectomy on the structure of the primate superior oblique muscle.

PURPOSE. Although cyclovertical strabismus in humans is frequently attributed to superior oblique (SO) palsy, anatomic effects of SO denervation have not been studied. Magnetic resonance imaging (MRI) and orbital histology was used to study the effects of acute trochlear (CN4) denervation on the monkey SO.

Fascicular specialization in human and monkey rectus muscles: evidence for anatomic independence of global and orbital layers.

Purpose: Connective tissue pulleys inflect the extraocular muscles (EOMs) and receive insertions from some fibers. The authors investigated insertions and anatomic relationships of fiber fascicles within rectus EOMs to clarify the relationship to their pulleys.

Methods: Two human and two monkey orbits were removed intact, serially sectioned in the coronal plane, histologically stained, and digitally photographed.

Horizontal rectus muscle anatomy in naturally and artificially strabismic monkeys.

Purpose: Structural abnormalities of extraocular muscles (EOMs) or their pulleys are associated with some forms of human strabismus. This experiment was conducted to investigate whether such abnormalities are associated with artificial or naturally occurring strabismus in monkeys.

Methods: Binocular alignment and grating visual acuities were determined in 10 monkeys representing various species using search coil recording and direct observations.

Fatal toxic shock syndrome associated with Clostridium sordellii after medical abortion.

Endometritis and toxic shock syndrome associated with Clostridium sordellii have previously been reported after childbirth and, in one case, after medical abortion. We describe four deaths due to endometritis and toxic shock syndrome associated with C. sordellii that occurred within one week after medically induced abortions.

Superior oblique muscle layers in monkeys and humans.

Purpose: Rectus and the inferior oblique extraocular muscles (EOMs) consist of orbital layers (OLs), inserting on connective tissues, and global layers (GLs), inserting on the sclera. This study was performed to clarify the anatomic relationships of the corresponding layers of the superior oblique (SO) muscle.

Methods: Two whole human and two monkey orbits were serially sectioned en bloc at 10-mum thickness in the coronal plane and stained for collagen with Masson's trichrome and for elastin with van Gieson's stain.

Demonstration of systematic variation in human intraorbital optic nerve size by quantitative magnetic resonance imaging and histology.

Purpose: To use magnetic resonance imaging (MRI) to measure the diameter along the course of the intraorbital optic nerve in living subjects and cadaveric specimens, and to validate measurements histologically in the same specimens.

Methods: Measurements of the intraorbital optic nerve were made in 23 living human subjects and in three formalin-fixed orbits using high-resolution, surface coil MRI in the coronal plane. Fixed orbits were then serially sectioned in the same plane, and stained by Masson's trichrome for digital morphometry of nerve diameter and densitometry of connective tissue constituents.

Evidence for a pulley of the inferior oblique muscle.

Purpose: This study was undertaken to investigate evidence for a connective tissue pulley constraining the path of the inferior oblique (IO) muscle.

Methods: From magnetic resonance images, the cross-sectional area, path, and orbital relationships of the human IO were determined in multiple gaze positions. Rectus pulleys were directly imaged with intravenous gadodiamide contrast.

Extraocular connective tissue architecture.

Extraocular muscle pulleys, now well known to be kinematically significant extraocular structures, have been noted in passing and described in fragments several times over the past two centuries. They were late to be fully appreciated because biomechanical modeling of the orbit was not available to derive their kinematic consequences, and because pulleys are distributed condensations of collagen, elastin and smooth muscle (SM) that are not sharply delineated. Might other mechanically significant distributed extraocular structures still be awaiting description?An imaging approach is useful for describing distributed structures, but does not seem suitable for assessing mechanical properties.

Quantitative analysis of the structure of the human extraocular muscle pulley system.

Purpose: Extraocular muscle (EOM) paths are constrained by connective tissue pulleys serving as functional origins. The quantitative structural features of pulleys and their intercouplings and orbital suspensions remain undetermined. This study was designed to quantify the composition of EOM pulleys and suspensory tissues.