Orbital Anatomy Research Articles

Spectrum of infantile esotropia in primates: Behavior, brains, and orbits

Recent studies of human infants have described a spectrum of early-onset esotropia, from small angle to large heterotropias. We report here a similar spectrum of early-onset esotropia in infant monkeys, with emphasis on the relationship between visuomotor deficits, central nervous system circuitry, and orbital anatomy. Eye movements were recorded in macaque monkeys with natural, infantile-onset esotropia (n = 7) and in control monkeys (n = 2) to assess alignment, latent nystagmus, dissociated vertical deviation (DVD), and pursuit/optokinetic nystagmus (OKN) asymmetries. Acuity was measured by preferential-looking technique or spatial sweep visual-evoked potentials. Geniculo-striate pathways were then analyzed with neuroanatomic tracers and ocular dominance column labels. Extraocular muscles were examined by high-resolution magnetic resonance imaging (MRI) and anatomic sectioning of whole orbits. Esotropia ranged from 4 to 13.5 degrees (7-24(Delta)) with fixation preference (if any) varying idiosyncratically (as in human). Severity of ocular motor dysfunction (ie, nystagmus velocity, DVD amplitude, pursuit-OKN nasal bias index) increased as the magnitude of esotropia angle. Animals with greater ocular motor deficits tended to have greater visual area V1 (striate cortex) neuroanatomic deficits, evident as fewer binocular horizontal connections in V1. Orbital MRI/anatomic analysis showed no difference in horizontal rectus cross-sectional areas, muscle paths, innervation densities, or cytoarchitecture compared with normal animals. The infantile esotropia spectrum in nonhuman primates is remarkably similar to that reported in human infants. Concomitant esotropia in these primates cannot be ascribed to abnormalities of the extraocular muscles or orbit. These findings, combined with epidemiologic studies of humans, suggest that perturbations of cerebral binocular pathways in early development are the primary cause of the infantile esotropia syndrome.

Surgical Anatomy of the Chinese Orbit

To describe the metric measurements and normal anatomic variants in Chinese bony orbits. Orbital osteology was studied in 194 orbits from 97 Chinese skulls. Morphologic observations and metric measurements were made to elucidate the variations of the orbital bony anatomy and to localize important fissures and foramina within the orbit. Sexual dimorphism and side asymmetry of orbital features were analyzed. Results were then compared with data from other populations. The details of the orbital osteology in Chinese are described. Most orbital features show anatomic variations in terms of their existence, quantity, and location. Anatomic variants including quadruple and extrasutural posterior ethmoidal foramen are described for the first time. Side asymmetry and sexual dimorphism (male larger than female) are demonstrated in some orbital features. Compared with white and American populations, orbital measurements are generally smaller in Chinese, probably related to their smaller orbital size. The Chinese orbital osteology demonstrates considerable variability. The newly described anatomic variants found on the posterior ethmoidal foramen may affect surgical procedures related to the medial orbital wall. Sexual dimorphism and ethnic variations of the orbital bony anatomy may affect surgical approach to orbital diseases in different populations.

Surgery of the Globe and Orbit

Orbital anatomy and the indications and surgical techniques for a variety of small animal orbital/globe surgical procedures are discussed. Details of the more common orbital surgical procedures, including ocular evisceration, intrascleral prosthesis implantation, enucleation, and proptosis repair, are given. Common complications and postoperative considerations for these procedures are also discussed with an emphasis on the practical aspects.

Use of High-Resolution Microscopy Coil MRI for Depicting Orbital Anatomy

Objective: High-resolution MRI (HR-MRI) is a powerful non-invasive tool that provides images of higher spatial resolution and enables visualization of tissues previously unidentified with conventional techniques. The utilization of HR-MRI in the eye and orbit is essential due to the minute structure with great tissue diversity. The purpose of this study is to investigate the use of a novel surface coil and to explore the potential of this approach to depict normal anatomy. Methods: MR images were acquired using a commonly available 1.5T scanner. Ten normal volunteers were imaged using a surface microscopy coil of 47 mm inner diameter. T1- and T2-weighting and fat suppression techniques were used. HR-MR images were compared with conventional head coil MR images. Results: Overall exquisite anatomic detail of the eye and orbit is revealed. The in-plane resolution was 312 μ m and the displayed pixel dimension 156 μ m. Previously unobserved distinction of the globe layers and muscle groups is possible. To our best knowledge, our group was the first to demonstrate Tenon's capsule and the tarsal plate with MRI. The ciliary body and zonules of the lens are clearly visible. The superior muscle group is illustrated, being apparently divided into its components, namely the superior rectus and the levator palpebrae superioris muscles. Finally, the retrobulbar fat and parts of its connective tissue are depicted. Conclusion: High-resolution microscopy coil MRI improves the image resolution dramatically and enables a detailed tissue depiction of the orbital and globe structures. Therefore, its introduction in routine clinical use can facilitate diagnosis and pre-operative planning in challenging cases.

Evaluation and Treatment of Zygomatic Fractures

Orbitozygomatic fractures are some of the most common facial fractures evaluated and treated by plastic surgeons. A considerable debate remains surrounding the manner of evaluation and appropriate treatment modalities. On the one hand, some would suggest that few fractures need formal open reduction and internal fixation, whereas others would argue that the pull of the strong masseter muscle ultimately leads to inferior and lateral rotation of the zygoma, which justifies open reduction and internal fixation of most fractures excepting those fractures that are nondisplaced at all points of articulation. The authors hope to shed some light on these issues by conveying their perspective on these fractures that has developed over several decades while servicing a single, major Level I trauma center. In general, the authors feel that through a detailed evaluation including an accurate physical examination of the face and orbit combined with detailed computed tomographic scanning of the craniofacial skeleton and soft tissues, an appropriate treatment plan can be generated. The common goal among all treatment plans should be the exact three-dimensional restoration of the disturbed anatomy, that is, anatomical reduction and the need for accurate restoration of orbital anatomy and volume when necessary.

Peribulbar Anesthesia for Blepharoplasty

Peribulbar anesthesia for inferior blepharoplasty was used successfully in 788 selected cases over the past 9 years. This technique is largely accepted for ophthalmologic procedures, but is not yet specifically used for blepharoplasty. In the past 9 years, 788 patients ages 36 to 77 years were submitted to inferior peribulbar anesthesia for blepharoplasty procedures. Of these patients, 623 (79%) were women and 165 (21%) were men. The anesthetic procedure is performed using a needle introduced at the junction of the medial two-thirds and the lateral third of the inferior orbital rim (point A). With the patient staring forward, the needle is introduced through the lid at point A. It enters the orbital cavity just above the orbital floor periosteum until the globe equator is minimally trespassed (depth, approximately 31 mm). There, 3 ml of the local anesthetic solution (2% lidocaine + 0.5% bupivacaine) is slowly injected. None of our treated patients reported pain or discomfort during or after the surgical procedure. Immediately after inferior peribulbar anesthesia, chemosis was observed in 17 cases (2.2%) and orbital hematoma in 3 cases (0.4%). Diplopia, or a slight imaging distortion lasting a few hours may occur after inferior peribulbar anesthesia. Inferior peribulbar anesthesia for blepharoplasty offers surprising results. The surgical procedures are performed pain free, leaving the patients completely relaxed and allowing an easier surgical procedure. This technique should be performed only by highly skilled anesthesiologists or surgeons with a perfect knowledge of the complex orbital anatomy.

S212: Orbital Surgery for the Oral and Maxillofacial Surgeon: Anatomical and Imaging Considerations

The orbit is one of the most fascinating areas of anatomical enquiry because it exhibits unparalleled features of architectural organization to accommodate the complex demands of vision. Orbital involvement in trauma, infections as well as neoplastic processes spreading from the maxillofacial region, and during the course of certain orthognathic surgical techniques requires a thorough understanding of orbital anatomy by the Oral and Maxillofacial surgeon. Although the core principles of orbital surgery have not radically altered during the past decade, improvement in our knowledge of orbital anatomy has improved our understanding of orbital pathophysiology and has brought refinement to orbital surgery. Multislice CT and High resolution MR display orbital anatomy with considerable clarity and provide most of the information needed. However, the nature of pathological process and the compact anatomy of the orbit sometimes necessitate the use of more than one modality with creative juxtaposition of information through image data management to permit a lucid interpretation of the characteristics of orbital pathology. In this presentation, we will provide a comprehensive survey of orbital anatomy with particular emphasis on those aspects of particular relevance in orbital surgery. The application of various imaging modalities to display normal orbital anatomy and delineate specific changes induced by various pathological processes will be demonstrated and discussed. Case studies of common as well as uncommon orbital pathology from our experience illustrating specific problems and challenges in orbital surgery will be presented.

Retrobulbar hemorrhage

Retrobulbar hemorrhage is an uncommon, vision-threatening complication of orbit and eyelid surgery. We review the incidence of retrobulbar hemorrhage, risk factors, orbital anatomy, pathophysiology, diagnosis and treatment options. Preoperative, intraoperative and postoperative measures to prevent retrobulbar hemorrhage are discussed, and a treatment algorithm is presented.

Orbital Syndromes

The orbit is a complex anatomical structure with unique properties not observed in other regions of the body. Composed of seven bones, the orbit is filled by the eye, optic nerve, lacrimal gland, extraocular muscles, peripheral motor and sensory nerves, fat, arteries, and veins. All these structures are intimately related to one another within an intricate framework of connective tissue. A variety of traumatic, vascular, inflammatory, infectious, and neoplastic processes can affect the orbit and its structures. Aside from the many primary orbital diseases, systemic disorders and pathological processes from neighboring structures (eye, ocular adnexa, oral cavity, paranasal sinuses, and intracranial cavity) can involve the orbit. A careful history and complete physical examination, with special attention to the orbit and ocular adnexa, are required to identify subtle orbital abnormalities that otherwise could be overlooked or mistakenly contributed to a nonorbital process. This article reviews the pertinent orbital anatomy, discusses the clinical evaluation and manifestations of orbital syndromes, and highlights several important orbital syndromes germane to the neurologist, including thyroid-associated orbitopathy, nonspecific orbital inflammation (also known as inflammatory orbital pseudotumor), perineural orbital invasion of cutaneous squamous cell carcinoma, rhino-orbital-cerebral mucormycosis, and carotid-cavernous sinus fistula.

Spectrum of infantile esotropia in primates: Behavior, brains, and orbits

Introduction: Recent PEDIG studies have described a spectrum of early-onset esotropia (ET), from small variable angle to “classical” large heterotropias. We report here a similar spectrum of early-onset ET in infant monkeys, with emphasis on the relationship between visuomotor deficits, central nervous system circuitry, and orbital anatomy. Methods: Eye movements were recorded in macaque monkeys with natural (n = 3) and optically induced (n = 7) ET to assess alignment, disparity-vergence, latent nystagmus, DVD, and pursuit/OKN asymmetries. Acuity was measured by SSVEP and stereopsis thresholds established using random-dot stimuli. Geniculo-striate pathways were then analyzed with neuroanatomic tracers and metabolic labels. EOMs were examined by high-resolution magnetic resonance imaging and anatomic sectioning of whole orbits. Results: ET ranged from 4° to 25° (7–44Δ) with fixation preference (if any) varying idiosyncratically (as in human). Severity of ocular motor dysfunction (ie, vergence insensitivity, nystagmus velocity, DVD amplitude, nasotemporal gain asymmetry), and severity of stereopsis deficit related to ET angle and duration (regression analysis; p = 0.036). Animals with marked behavioral deficits tended to have marked V1 neuroanatomic deficits, evident as fewer binocular horizontal connections and denser metabolic suppression. Orbital MRI/anatomic analysis showed no EOM/pulley or cranial nerve end-plate anomalies compared with (n = 3) controls. Conclusions: The ET spectrum in nonhuman primates is remarkably similar to that reported in human infants. Concomitant ET in these primates cannot be ascribed to abnormalities of the extraocular muscles or orbit. These findings, combined with epidemiologic studies of human, indicate that perturbations of CNS binocular pathways in early development are the primary cause of the infantile ET syndrome.

Three dimensional digital atlas of the orbit constructed from multi-modal radiological images

The human orbit has numerous structures packed in a relatively small space, the study of which is essential and difficult due to complex three dimensional relationships. Available printed orbital atlases do not convey the three dimensional information and are not interactive. To overcome these limitations, we built a digital 3D orbital atlas presented in axial, coronal and sagittal planes, and as three dimensional geometric models of the muscles, bones, and eyeball. The bone models are from a CT scan, the muscle and optic nerve from a MR scan, and other components that cannot be distinguished radiologically are modeled as geometric primitives from anatomic literature. All multi-modal data including the models and images are registered into the same space to form a complete atlas. All structures in the atlas are labeled with their names. An atlas browser is developed for user-friendly manipulation and presentation of the atlas content. Each structure can be turned on or off, rotated, zoomed, or moved, either individually or in unison with other selected structures. Thus, the relationships between different structures can be studied in greater depth. The method developed to build the orbital atlas is general and can be used to create other atlases or to build patient specific geometric models. The orbital atlas may be used for studying the orbital anatomy, as a reference guide for practitioners, and as a base for simulation of orbital surgery.

High-Resolution Magnetic Resonance Imaging of the Upper Eyelid: Correlation with the Position of the Skin Crease in the Upper Eyelid

Purpose: The position and appearance of the upper eyelid crease is one of the challenges in eyelid surgery. The aim of this study was to compare the clinical appearance of the upper eyelid crease with its anatomy, including the position of the levator, the septum, and the orbital fat as determined by Magnetic Resonance Imaging (MRI). Materials and methods: Oculoplastic examination was performed in normal volunteers of the same age with different appearances of the upper eyelid. MRI (Intera 1.5 T, Philips, the Netherlands) was carried out with both head and surface coils in all volunteers. Subjects were asked to keep their eyes closed during the whole procedure, thus reducing artefacts due to eyeball movements. The protocol lasted 8 minutes and included a multiplanar scout to obtain T1-weighted 3D-images. Thin sagittal T2 sequences were obtained along the plane of the optic nerve and focused on both orbits, allowing a precise analysis of the orbital content and eyelid anatomy. Results: Six volunteers were included in this prospective study, three of Caucasian origin and three of North African, Central African and Asian origin, respectively. We distinguished two appearances of the crease: in some cases, the superior eyelid sulcus was convex, while in other cases it was concave. The superior eyelid fold was either high or low. Two Caucasian subjects had a deep, concave superior eyelid sulcus with a high crease. This crease appearance was correlated with a short concave appearance of the septum, which pulled back the pre-aponeurotic fat. The non-Caucasian volunteers all had a convex superior eyelid sulcus. The orbital septum insertion was low on the levator aponeurosis, and the orbital fat pad drooped onto the levator muscle, accounting for the convexity of the upper eyelid sulcus. A skin fold was formed by redundant skin over the crease. Conclusions: MRI provides excellent images and allows a good analysis of the upper eyelid components. It permits a detailed analysis of the architecture for a better understanding of its appearance and of the crease position, although further investigation with a larger number of volunteers is required.

Topographical CT-data analysis of the human orbital floor

The aim of this study was to evaluate the topographical anatomy of the human orbital floor for the production of prefabricated implants on the basis of computer tomography data. A database of 279 CT scans of Caucasian patients without traumatic deformation of the midface was analysed. 3D-image segmentation of the midfacial skeleton was performed using a computer-assisted protocol. A virtual plane (50 × 50 mm 2) was constructed using defined landmarks above the orbital floor. An automated procedure was used to measure the distance between the orbital floor and the constructed plane at 400 distinct points. A mathematical algorithm was used to analyse the data, and to calculate a map of the orbital floor. Statistical analysis of the data revealed that orbital floor topography could be classified as distinct clusters. There were 12 variations of orbital floor anatomy: three unique patterns of the orbital floor for the right orbit and three corresponding patterns for the left side, all of which varied between the sexes. The 12 patterns were constructed with a statistical confidence interval of 1.36 ± 0.6 mm.

Update on orbital anatomy

The orbit is a confined space bounded by four bony walls. Apart from the globe, orbital fat, and extraocular muscles it contains many important neurovascular structures. It is intimately related to the paranasal sinuses as well as the anterior and middle cranial fossae. Consequently, sinus pathology and intracranial disease may spread to involve the orbit and the converse applies. A thorough understanding of orbital anatomy is essential to fully appreciate the effects of disease on the orbit and is of paramount importance for performing safe orbital surgery. The anatomy of the orbit is discussed with reference to relevant orbital disease.

Upper and lower eyelid reconstruction: the year in review

Depending on the size, location, and extent of defects, a myriad of surgical approaches may be utilized to repair the eyelids. An understanding of the principles of lid reconstruction as well as orbital and periorbital anatomy is essential when approaching the repair of eyelid defects. While principles of eyelid reconstruction have been established, achieving good functional and aesthetic reconstruction remains challenging. This review examines the methodology of reconstructing eyelid defects, as reported over the last year. Eyelid reconstruction continues to encompass a wide range of reconstructive options. Reports range from simple modifications of traditional techniques to the use of complex flaps and grafts. While set algorithms have been proposed regarding eyelid reconstruction, the method of choice will ultimately depend on a combination of factors, including availability of tissues, and a surgeon's experience with the available modes of reconstruction.

Comprehensive therapy of orbital tumor

Although the popularization of the knowledge of orbital disease is increasing, some issues such as surgery complications, recurrence, metastases may significantly affect the outcome of treatment. The new concept of comprehensive therapy offers an integrated individual therapy to patients. Application the concept in clinical practice is a key measure to improve the cured rate. In order to enhance the rate of cure of orbit tumor, it is essential for ophthalmologist to get standardized training in the diagnosis, treatment of orbital disease, and familiar with orbital anatomy and other knowledge related to orbit diseases.

Orbital regional anesthesia.

Orbital regional anesthesia is a useful and safe modality for providing excellent operating conditions for the surgeon and painless, pleasant circumstances for the patient. It is especially suited for patients who are extremely sensitive and who could not tolerate topical anesthesia or a sub-Tenon's block without deep sedation. Both intraconal and extraconal techniques can be used safely and effectively if proper precautions are taken to enter the safest areas of the orbit and to avoid the vascular areas and the deep orbit where structures are tightly packed and thus more easily harmed. Thorough knowledge of orbital anatomy and understanding of the globe-orbit relationship of every patient are necessary to perform this form of regional anesthesia. In addition, knowledge of the effects and side effects of the anesthetics and adjuvants is also required.

Modélisation informatique tridimensionnelle de la cavité orbitaire et des paupières

To develop a virtual model of the orbital cavity and the eyelids using a three-dimensional model.Amapi Designer 7 and Carrara 3 Studio (Eovia, Mountain View, CA, USA) software were used to obtain 3D models of the orbital cavity and the eyelids. Three-dimensional creation is divided into two main processes. In the modeling process, a 3D model of the orbit, the arterial supply, and the eyelids are created using polygonal meshes and surgical tools with parametric surfaces. In the rendering process, colors are arbitrarily chosen to make elements in the model easier to read. A virtual camera is adjusted and light sources are created to produce virtual simulations of the orbit and the eyelids.Surgical techniques were illustrated with 3D models. Ptosis surgery (resection of the levator muscle and Müller's muscle conjunctival resection) and the transconjunctival approach to lower eyelid blepharoplasty were described step by step.Three-dimensional models have applications in many medical fields, providing representation of anatomical structures. They can be used to depict the anatomy of the orbital region in a realistic way. Three-dimensional computer-generated images are an aid in teaching residents in orbital anatomy and surgery.

Underdeveloped extraocular muscles in the naked mole rat (Heterocephalus glaber)

The extraocular muscles (EOM) are the final effector arm of the ocular motor system. These small muscles have a unique embryological origin and phenotype. Their diversity is highlighted by their resistance to some neuromuscular disorders (muscular dystrophy, ALS) and increased susceptibility to others (myasthenia gravis and mitochondrial myophathies). The naked mole rat (NMR) is a subterranean rodent with a reduced visual system; it is an ideal model to examine the potential codependence of full EOM and visual system phenotype development and evolution. Our goal was to compare the structural features of NMR EOMs to those of a similar sized rodent with a fully developed visual system. Whole orbits and EOMs were dissected from perfusion-fixed adult NMR and C57BL mice and examined by light and electron microscopy. NMR orbital anatomy showed smaller EOMs in roughly the same distribution around the eye as in mouse and surrounded by a very small Harderian gland. The NMR EOMs did not appear to have the two-layer fiber distribution (orbital and global) seen in mouse EOMs; fibers were also significantly smaller (118 vs. 551 sq um in mouse EOMs). Myofibrillar density was less in NMR EOMs, and triad and other membranous structures were rudimentary. Finally, mitochondrial volume density was significantly less in NMR EOMs than in mouse EOM (4.5% vs. 21.2% respectively). These results demonstrate that NMR EOMs are smaller and less well organized than those in a rodent with a fully developed visual system. It is likely that at least some aspects of EOM organization depend on visual experience.

Prosthetic Contact Lenses: Adventure or Miracle

To show that if fitted and handled properly, iris painted contact lenses can be good cosmetic prostheses for disfigured or blind eyes for which no evisceration or enucleation is indicated. Twenty patients with an opaque cornea were enrolled in this study. All patients underwent detailed ophthalmologic examinations, including corneal topography and keratometry. The close-up photographs of healthy eyes of the subjects were taken by a camera with a mounted macro lens under daylight. Twenty custom hand-painted contact lenses (Net Lens, Istanbul, Turkey) were selected from the catalog, made according to the photographs, and applied to the patients. Fitting and centration were examined by slitlamp biomicroscopy. Because of troubles in fitting and centralization, contact lenses could not be applied in three of the patients. In the remaining 17 patients, the lenses were applied successfully. All eyes achieved the desired cosmetic and anatomic result. Besides providing superior cosmesis to evisceration or enucleation, prosthetic contact lenses significantly improve the social relationships and well-being of patients. Fitting a prosthesis over a disfigured or an absolute (blind) eye could be a successful remedy for maintaining the integrity of the orbital anatomy, enhancing the cosmetic appearance, and accelerating the rehabilitation of patients with disfigured blind eyes.