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PubMedDate not supplied

The peanut orbit: a modified elliptical orbit for single-photon emission computed tomography imaging.

The front collimator surface of a conventional single-photon emission computed tomography (SPECT) detector system transcribing an elliptical orbit to approximate body contour could, under certain circumstances, penetrate the ellipse and make patient contact. The problem is associated both with the large front surface dimensions of tomographic cameras and the need to maintain the camera perpendicular to a radius through the axis of rotation. To aid in the development of an improved body contour orbit, software has been developed to simulate SPECT imaging systems. A major feature of the algorithms is a spatially calibrated graphic representation of the pallet, patient and orbit of the camera head. Based on computer simulations performed with this software, a modified elliptical orbit has been proposed for patient contour SPECT scanning on two different types of tomographic acquisition systems: a dual camera, rotating ring system and a single camera, multimotion stand system. This peanut orbit has the advantage of minimizing collimator patient distance, as does the elliptical orbit, but also compensates for camera motion that could potentially produce patient contact. Versions of the peanut orbit algorithms have been installed and are operational on clinical systems similar to those that were simulated. The ring-based gantry system (with cameras mounted on cantilevered arms) requires additional software to correct for translational shift in the field of view as a function of radial distance from the center of the system. This is done during uniformity correction. Standard unmodified backprojection software is used for reconstruction. The peanut orbit may represent an improved approach to body contour imaging in rotational SPECT.

Algorithms↗

PubMed1999

Use of an orbital epidural catheter to control pain after orbital implant surgery.

BACKGROUND: The surgical placement of orbital implants for eviscerations, enucleations, and secondary implantations can cause severe postoperative pain that may not be relieved with high doses of narcotics. We analyzed the effectiveness of a method for postoperative pain control in orbital implant surgery using an orbital epidural pain catheter connected to a patient-controlled analgesia bupivacaine hydrochloride pump. METHODS: One hundred nineteen patients undergoing orbital hydroxyapatite implant surgery received placement of an orbital epidural catheter for the infusion of local anesthetics at the conclusion of their surgery. Patients were asked to gauge their level of comfort into the following 3 categories: total, some, or no pain relief in the first week after surgery. A separate numerical grading scale was used to further quantitate pain. Blood samples were collected in 4 patients to assess the systemic levels of bupivacaine. RESULTS: Most patients (88.2%) responded with total or some pain relief, with only 11.8% suffering severe pain. The mean numerical pain score was 2.8, within a range of 0 (no pain) to 10 (severe pain). The average plasma bupivacaine level in the 4 patients in whom this was measured was 0.38 microg/mL, which is well below the toxic level of 4.0 microg/mL. Furthermore, there were only 5 minor complications caused by the catheters, ie, 1 retrobulbar hemorrhage and 4 catheters that did not work. No permanent problems arose from any of the complications. CONCLUSIONS: The orbital epidural pain catheter is an effective means to achieve postoperative pain control after orbital implant surgery. The simple technique of insertion and management of the catheters was well tolerated in our patient population.

Adolescent↗

PubMed1995

The combined pterional and orbitocygomatic approach to extensive tumours of the lateral and latero-basal orbit and orbital apex.

Using standardized transcranial (pterional, subfrontal, fronto-orbital) approaches, complete removal of tumours located in the latero-basal aspect of the orbit and the lateral orbital apex with or without extension to the temporal fossa is not possible or can only be achieved if excessive traction is applied to the contents of the orbit and the brain. In contrast, the combined pterional and orbitocygomatic approach provides unhindered access to the superior, lateral and latero-basal orbit, superior and inferior orbital fissure and, if required, to the temporal fossa including the foramina ovale and rotundum. Six patients with extensive orbital lesions underwent surgery using this technique with good operative results.

Adult↗

PubMed2006

Orbital stress analysis--Part I: Simulation of orbital deformation following blunt injury by finite element analysis method.

PURPOSE: The purpose of this study was to develop a 3-dimensional finite element model (FEM) of the human orbit, housing the globe, to predict orbital deformation in subjects following a blunt injury. MATERIALS AND METHODS: A FEM of the human orbit including the eye, fatty tissues, and extraocular muscles was constructed. Simulations were performed with a computer using the finite element software NISA (EMRC, Troy, MI). The orbit was subjected to a blunt injury of a 0.5 kg missile with 30 m/s velocity. The FEM was then used to predict principal and shear stresses/strains at each node position. RESULTS: Two types of orbital deformation were predicted during different impact simulations: a) horizontal distortion and b) rotational distortion. Stress values ranged from 112.12 to 262.3 MPa for the maximum principal stress, from -226.8 to -552.1 MPa for the minimum principal stress, and from 111.3 to 343.3 MPa for the maximum shear stress. CONCLUSION: This is the first finite element study that demonstrates different and concurrent patterns of orbital deformation in subjects following a blunt injury. FEM is a powerful and invaluable tool to study the multifaceted phenomenon of orbital deformation.

Biomechanical Phenomena↗

PubMed1999

Orbital vascular malformations: a consensus statement on terminology and its clinical implications. Orbital Society.

PURPOSE: Orbital venous anomalies and lymphangiomas have been generally classified on morphologic grounds. However, conflicting concepts of these lesions have hampered scientific dialogue and confused clinicians, with occasionally serious consequences for patients. As a step toward uniform nomenclature and better communication, a consensus on the terminology of orbital vascular malformations was sought among the members of the Orbital Society. METHODS: A classification of orbital vascular malformations based on their hemodynamic relationships, as revealed by clinical and imaging features, was presented, discussed, and adopted at the 1998 Annual Meeting of the Orbital Society. A consensus statement was drafted and distributed to all members. The statement was then modified in accordance with members' responses, which included minor stylistic recommendations but no substantive dissent. RESULTS: Orbital vascular malformations may be classified according to their hemodynamic relationships as no flow, venous flow, and arterial flow lesions. Assignment to each group is based on pertinent clinical and imaging criteria. Mixed forms with both venous and no flow components are grouped within the venous flow category to emphasize the clinical importance of that relationship. CONCLUSIONS: A hemodynamic classification of orbital vascular malformations emphasizes features most germane to their management. It should reduce the clinical confusion resulting from purely morphologic differentiation. Widely accepted definitions may allow a better comparison of therapeutic protocols for these troublesome lesions.

Arteries↗

PubMed2005

Free orbital fat graft to prevent porous polyethylene orbital implant exposure in patients with retinoblastoma.

PURPOSE: To determine if porous polyethylene orbital implant (Medpor) exposure can be prevented in retinoblastoma patients when the implant is placed in combination with a free orbital fat graft over the anterior surface of the implant. METHODS: Free orbital fat grafts were performed after enucleation and Medpor implantation, and results were compared with patients who underwent conventional enucleation and Medpor implantation without an orbital fat graft. RESULTS: Although implant exposure occurred in 13 of 39 eyes (33.3%) that had conventional enucleation and Medpor implantation, exposure did not develop in any of the 38 eyes that had the combined procedure with a free orbital fat graft. CONCLUSIONS: These findings suggest that a free orbital fat graft is a simple, effective way to prevent orbital implant exposure in patients requiring enucleation and Medpor implantation.

Adipose Tissue↗

PubMed1980

Palliative orbital decompression for metastatic melanoma to the orbit.

Although relatively rare, metastatic carcinomas to the orbit are the second most common orbital neoplasm in the adult. There are only ten cases reported in the literature of cutaneous melanoma metastatic to the orbit and, of these, only two had disease involving both orbits. This paper presents the third case of bilateral orbital melanoma; however, in this case, the primary site was the uveal tract in the first eye, with contralateral involvement being a metastasis of the orbital primary. The patient developed severe unilateral proptosis in his only seeing eye with progressive loss of vision. A palliative orbital decompression was performed which successfully restored visual acuity for an extended period of time. A brief discussion of the rationale for this procedure in this type of case is presented.

Ciliary Body↗

PubMed1990

Orbital compartment syndrome. Direct measurement of orbital tissue pressure: 1. Technique.

Many disorders of the orbit produce an increase in intraorbital pressure, which may result in the development of an orbital compartment syndrome and visual loss. Traditionally, orbital tension is assessed clinically by indirect means based on retrodisplacement of the globe. The authors describe their experience with the "slit-catheter" technique for direct tissue pressure measurement as applied to the orbit. The preliminary results indicate that normal orbital pressure ranges from 3.0 to 6.0 mm Hg. In patients with Graves' orbitopathy the values ranged from 7.0 to 15.0 mm Hg. The results suggest that the technique may have many exciting possibilities as a clinical research tool in orbital disease, and its use will result in better understanding of orbital compartment syndromes.

Equipment Design↗

PubMed1995

[Orbital varix presenting orbital apex syndrome].

On 7 July 1993, a 61 year-old female presented a seven-day history of double vision and retro-ocular pain. Neurological examination on admission demonstrated right oculomotor palsy and pain in the right frontal nerve. Routine CT scan and MRI disclosed no abnormalities. Her symptoms deteriorated progressively and increased in severity, resulting in complete ptosis and visual disturbance in the right eye, for which she was hospitalized. Angiography also failed to demonstrate any lesion. Herrical CT scan demonstrated a small mass lesion at the right orbital apex. A frontotemporal extradural approach operation was performed on July 6, 1993. The anterior clinoid process and minor wing of the sphenoid were drilled to expose the optic canal and the superior orbital fissure. When the periorbita just beside the optic sheath was opened, a large vein was observed to be impinging on the optic nerve and nerves which pass through the superior orbital fissure. This vein was carefully dissected, coagulated and removed. The postoperative course was uneventful. Her severe retro-ocular pain completely disappeared immediately after the operation. Although complete remission of ptosis and return of eye movements to normal were noted, her visual acuity is at present limited to hand movement. Orbital varix is a common cause of unilateral intermittent proptosis. However, there has been no report in the literature of orbital varix with orbital apex syndrome as the initial clinical appearance. In this type of patient with orbital varix and retrobulbar hemorrhage or impairment of intraorbital nerves, surgical intervention using a transcranial approach to the lesion should be undertaken.

Cranial Nerve Diseases↗

PubMed1997

[Orbital neurinoma presenting orbital apex syndrome].

A 75-year-old man presented a twelve-day history of double vision and retro-ocular pain with rapid deterioration of visual acuity. Neurological examination on admission demonstrated right oculomotor palsy and abducence palsy, visual loss in the right eye, and hypesthesia and pain in the right supraorbital nerve. CT scan and MRI disclosed a mass in the right orbital apex. An emergency operation via a frontotemporal extradural approach was performed to decompress the optic nerve. The anterior clinoid process and minor wing of the sphenoid were drilled to expose the optic canal and superior orbital fissure. When the periorbita just beside the optic sheath was opened, a grayish colored mass was observed beneath the superior rectus muscle. The mass was dissected from the surrounding intraorbital tissue and was removed completely. The postoperative course was uneventful. The patient experienced complete disappearance of the ocular pain and complete restoration of his visual acuity. Orbital neurinoma is a benign tumor accounting for between 2.1 and 6.8% of all orbital tumors in the large series. The salient clinical symptom is exophthalmos followed by mass palpability. However, an orbital neurinoma presenting orbital apex syndrome is quite rare. In the case with orbital apex syndrome, it is sometimes impossible to recover visual acuity even though the optic nerve decompression is promptly performed. In such a case, only an emergency approach to the lesion can rescue the visual acuity.

Abducens Nerve↗

PubMed2003

Combined endoscopic medial and inferior orbital decompression with transcutaneous lateral orbital decompression in Graves' orbitopathy.

PURPOSE: To determine the clinical efficacy and morbidity of combined endoscopic transnasal medial and inferior wall orbital decompression performed in conjunction with transcutaneous lateral orbital decompression. DESIGN: Retrospective noncomparative case series. PARTICIPANTS: Thirty-four subjects (64 orbits) underwent combined orbital decompression procedures for treatment of Graves' orbitopathy. INTERVENTION: Transnasal endoscopic medial wall and floor with simultaneous transcutaneous lateral orbital decompression. MAIN OUTCOME MEASUREMENTS: Ocular motility, visual acuity, and exophthalmometry. RESULTS: No new ocular motility disturbances occurred. There was a mean gain of 0.7 Snellen lines in acuity (range +9 to -10 lines). A mean proptosis reduction of 4.2 mm was observed (range 1-9 mm). CONCLUSIONS: Combined endoscopic transnasal medial and inferior orbital wall decompression done in conjunction with transcutaneous lateral orbital decompression carries a low risk of morbidity, including new onset motility disorders, and yields anatomic retropulsion of the globe that is comparable to other methods.

Adolescent↗

PubMed2004

Orbital pythiosis: a non-fungal disease mimicking orbital mycotic infections, with a retrospective review of the literature.

In the past decade there have been four well-documented cases of orbital pythiosis caused by Pythium insidiosum. All were recorded in apparently healthy children. Although pythiosis seems to be a rare infection in humans, we recently conducted a review of the medical literature to investigate misdiagnosed cases of orbital pythiosis in the past 100 years in children. To track putative cases of orbital pythiosis, we first identified orbital cases initially diagnosed as fungal infections. We were particularly interested in cases (a) involving apparently young healthy hosts, (b) the presence of hyaline, aseptate hyphal elements in the infected tissues, (c) the morphological features of the hyphal elements, (d) the presence of an eosinophilic granulomatous reaction with the Splendore-Hoeppli phenomenon around the mycelial elements, (e) resistance to antifungal therapy, (f) outcome after therapy, if any, and (g) cultural strategies. This study showed that indeed, there had been five other recorded cases of orbital infections, all in young children in the USA, with characteristics consistent with infections caused by P. insidiosum. The reports had described those cases of orbital-cranial-arterial diseases as patients with aspergillosis (one case), penicilliosis infection (one case), and zygomycosis (three cases). We reviewed those anomalous cases and discuss details about their clinical, pathologic, therapeutic, and etiologic evidence used to reclassify them as putative cases of orbital pythiosis.

Aspergillosis↗

PubMed2006

The survival of freely grafted orbital fat on porous polyethylene orbital implants in the rabbit.

PURPOSE: To investigate the long term survival of orbital fat grafted on a Medpor implant as a method of preventing porous polyethylene orbital implant (Medpor) exposure in anophthalmic sockets. METHODS: In one orbit in each of 8 rabbits, a small amount of retrobulbar orbital fat was grafted between the anterior surface of the Medpor implant and overlying conjunctiva, during the enucleation and Medpor implantation procedure. Two rabbits were sacrificed at 2, 4, 8 and 12 weeks postoperatively and grafted orbital fats were examined by light microscopy. RESULTS: Grafted orbital fat was well-maintained at 2 and 4 weeks, postoperatively. However, fat amounts were significantly reduced at 8 weeks, and viable fat was barely visible at 12 weeks. CONCLUSIONS: In rabbits, orbital fat grafted on Medpor implants was gradually resorbed, and the fat-occupied volume was not maintained.

Adipose Tissue↗

PubMed1987

The acute orbit. Preseptal (periorbital) cellulitis, subperiosteal abscess and orbital cellulitis due to sinusitis.

The clinical picture of an acute orbit, as manifest by preseptal cellulitis, subperiosteal abscess or orbital cellulitis, is still frequently seen in ENT practice. The commonest cause is sinusitis and the authors advocate early surgical intervention in acute orbits due to sinusitis. Clinically, it can be difficult to distinguish between a subperiosteal abscess and orbital cellulitis and a CAT scan may be helpful. Surgically, a subperiosteal abscess is the more important (and probably more frequent) entity as it may require drainage. It may be suspected in an acute orbit which progresses rapidly or fails to settle on treatment and it may require drainage to allow the condition to resolve and avoid potentially damaging sequelae. A classification of the stages of the inflammatory processes seen in the acute orbit is given and the management of 34 cases due to sinusitis is discussed. The other causes of acute orbits are discussed and the further complications that may occur are also mentioned. Blindness, cavernous sinus thrombosis and cerebral involvement are still frequently recorded and death may still occur.

Abscess↗

PubMed1984

The late treatment of vertical orbital dystopia resulting from an orbital roof fracture.

Traumatic fracture of the orbital roof is uncommon and it may be unrecognized at the time of injury. In this article we describe a patient with progressive vertical orbital dystopia four years after he sustained a fracture of his "frontal" bone. Surgical exploration revealed an orbital roof fracture complicated by a chronic dural leak. An intracranial-extracranial approach through a modified frontal craniotomy provided excellent visualization to elevate the bony orbit and globe safely and repair the dural tear. Our study illustrates the need to correct residual soft tissue deformity at a second operation. Orbital roof fracture is a complex injury and is best treated by a multispecialty team using the methods learned from the treatment of patients with congenital orbital dystopia.

Child↗

PubMed2004

Parallel, linear-scaling building-block and embedding method based on localized orbitals and orbital-specific basis sets.

We present a linear scaling method for the energy minimization step of semiempirical and first-principles Hartree-Fock and Kohn-Sham calculations. It is based on the self-consistent calculation of the optimum localized orbitals of any localization method of choice and on the use of orbital-specific basis sets. The full set of localized orbitals of a large molecule is seen as an orbital mosaic where each tessera is made of only a few of them. The orbital tesserae are computed out of a set of embedded cluster pseudoeigenvalue coupled equations which are solved in a building-block self-consistent fashion. In each iteration, the embedded cluster equations are solved independently of each other and, as a result, the method is parallel at a high level of the calculation. In addition to full system calculations, the method enables to perform simpler, much less demanding embedded cluster calculations, where only a fraction of the localized molecular orbitals are variational while the rest is frozen, taking advantage of the transferability of the localized orbitals of a given localization method between similar molecules. Monitoring single point energy calculations of large poly(ethylene oxide) molecules and three dimensional carbon monoxide clusters using an extended Huckel Hamiltonian are presented.

Journal Article↗

PubMed1991

Solitary extramedullary plasmacytoma of the maxillary antrum and orbit presenting as acute bacterial orbital cellulitis.

Orbital involvement by plasma cell tumours is rare. Orbital tumours do not generally present as an acute orbital inflammatory disease in adults, though tumours such as rhabdomyosarcoma may cause clinical signs similar to an acute orbital cellulitis in children. We describe a patient with bacterial orbital cellulitis and sinusitis who was found to have an extra-medullary plasmacytoma of the maxillary antrum and orbit and coexisting testicular seminoma.

Cellulitis↗

PubMed2000

Chronic, traumatic intraconal hematic cyst of the orbit removed through the fronto-orbital approach--case report.

A 22-year-old male presented with a chronic encapsulated intraorbital hematoma 3 months after blunt trauma to his left eyeball. Ophthalmological examination found the best corrected visual acuity was 4/20 in the left eye, and 20/20 in the right eye. The orbit exhibited exophthalmus and inability of the eye to move above the horizontal level. Orbital magnetic resonance imaging showed a fairly well-demarcated area in the medial aspect of the orbit appearing as hyperintense on T1-weighted images and isoto hyperintense on T2-weighted images. This area was believed to be hemorrhage. No other abnormalities were found. The diagnosis was hematic cyst. The cyst was approached through a left fronto-orbital route and its location identified within the periorbita and orbital fat. The cyst was removed partially. Histological examination demonstrated cystic accumulation of blood and breakdown products in a non-epithelium-lined fibrous capsule, compatible with hematic cyst. The presence of hemosiderin in the cyst wall suggested that the cyst was a chronically enlarging lesion. Hematic cysts of the orbit usually present as subperiosteal mass months to years after trauma. Surgical removal of the cyst wall rather than needle aspiration is recommended to prevent recurrence.

Adult↗