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At least 73 records · Page 4Linked to original sources
PubMed2004

Microprocessor-controlled optical stimulating device to improve the gait of patients with Parkinson's disease.

Different types of visual cue for subjects with Parkinson's disease (PD) produced an improvement in gait and helped some of them prevent or overcome freezing episodes. The paper describes a portable gait-enabling device (optical stimulating glasses (OSGs) that provides, in the peripheral field of view, different types of continuous optic flow (backward or forward) and intermittent stimuli synchronised with external events. The OSGs are a programmable, stand-alone, augmented reality system that can be interfaced with a PC for program set-up. It consists of a pair of non-corrective glasses, equipped with two matrixes of 70 micro light emitting diodes, one on each side, controlled by a microprocessor. Two foot-switches are used to synchronise optical stimulation with specific gait events. A pilot study was carried out on three PD patients and three controls, with different types of optic flow during walking along a fixed path. The continuous optic flow in the forward direction produced an increase in gait velocity in the PD patients (up to + 11% in average), whereas the controls had small variations. The stimulation synchronised with the swing phase, associated with an attentional strategy, produced a remarkable increase in stride length for all subjects. After prolonged testing, the device has shown good applicability and technical functionality, it is easily wearable and transportable, and it does not interfere with gait.

Aged↗
PubMed2003

Dirac-algebraic approach to the theory of device operators in polarization optics.

An alternative approach to the theory of polarization optical devices, based on the Dirac-algebraic formalism, is presented. The advantages of this treatment over the widespread Jones-matrix formalism are discussed. The operators of some basic homogeneous optical devices are expanded in their eigenbases and in the Cartesian basis. The global and spectral properties of some cascades of polarization devices are analyzed.

Journal Article↗
PubMed2000

Characterization of antiresonant reflecting optical waveguide devices by scanning near-field optical microscopy.

Silicon-based antiresonant reflecting optical waveguide (ARROW) devices were studied by means of a scanning near-field optical microscope. Various structures such as a Y junction of a Mach-Zehnder interferometer and a directional optical coupler were characterized, showing the propagation of the light inside the devices simultaneously with the topography. Scattering on the splitting point of the Y junction was shown, as well as a partial coupling of the light between the two branches of the coupler. Measurements on the decay length of the evanescent field were also performed to study the use of the ARROW waveguide for sensor purposes.

Journal Article↗
PubMed2003

Fabrication and performance of a medium-dependent SiO2/Si photonic heterostructure device.

An optical device based on a photonic bandgap heterostructure is designed, fabricated, and characterized. The sample contains two sets of Si/SiO2 photonic crystals with different periods. When the device is working in air, it reflects omnidirectionally both TE and TM mode lights at the wavelength near 1.3 microm. The reflectivity measured in the bandgap is higher than 98% in an incident angle range 0 degrees-70 degrees. When the device is surrounded with silica (n > 1.33), it permits the total transmission for the TM mode but prevents the TE mode from propagating, thus behaving as a polarization splitter. The experimental extinction ratio of the reflected TE/TM is approximately 31 dB. The uniformity of the device performance over a large sample area is demonstrated.

Journal Article↗
PubMed2003

Optical nonreciprocal devices with a silicon guiding layer fabricated by wafer bonding.

Optical nonreciprocal devices with a silicon guiding layer fabricated by wafer bonding are proposed. The optical nonreciprocal devices are composed of a magneto-optic waveguide with a magnetic garnet/Si/SiO2 structure. Nonreciprocal characteristics are obtained by an evanescent field penetrating into the upper magnetic garnet cladding layer. Several kinds of the optical nonreciprocal device are investigated with the magneto-optic waveguide and designed at a wavelength of 1.55 microm. As a preliminary experiment, wafer bonding between Gd3Ga5O12 and Si was studied. Wafer bonding was successfully achieved with heat treatment at 220 degrees C in H2 ambient.

Journal Article↗
PubMed1994

Tomographic time-of-flight optical imaging device.

Time-resolved optical imaging has been used to image phantoms, animals, and humans, and offers the potential for the production of functional images of human tissues, such as the oxygenation of brain during stroke. We had previously reported a transmission scanner, and now give an early report on conversion to a rotational tomographic scanner with a non-parallel ray geometry similar to early CAT scanners. Initial scans show that 1) spatial imaging in turbid media using time-of-flight measurements, non-recursive algorithms, and standard tomographic geometry is possible, 2) separation of absorbance and scattering as an image is attainable, a key step in performing spatially-resolved chemometric analysis, 3) imaging of multiple objects buried within scattering material is feasible, demonstrating that equations derived for homogeneous media can be applied in at least some cases to inhomogeneous media such as tissue-like phantoms, and 4) imaging of brain pathology produces recognizable images with sufficient resolution for diagnostic decisions. We conclude that optical tomography is feasible for clinical use and that conversion of the present mechanically scanning device to a clinical scanner should be possible with retention of the current processing algorithms. Such a clinical scanner should ultimately be able to generate images in a few minutes with centimeter resolution at the center of living human brain.

Algorithms↗
PubMed2004

[Devic's optic neuromyelitis and viral hepatitis type A. A paediatric case report].

INTRODUCTION: Devic optic neuromyelitis is a rare clinical disease that involves severe transverse myelitis and unilateral or bilateral optic neuropathy. Its pathogenesis would be explained by demyelinization triggered by bacterial or viral infections phenomena. According to several author, prognosis would be better in children. CASE REPORT: We report a case of optic neuromyelitis in an 8-year-old child with an uneventful history who was admitted because he suffered from flaccid tetraplegia and sudden decline of the visual acuity. The ophthalmologic examination revealed bilateral neuropapillitis. The medullary MRI visualized a spreading myelitis with bifocal arachnoiditis. Search for a precipitating infectious factor showed positive IgM for viral hepatitis A. With corticosteroid treatment the child achieved total recovery of vision and recovered motor and sensorial function of the upper limbs and the trunk. Paraplegia with sphincteral disorders persisted. CONCLUSION: This case characterized by the precipitating factor (hepatitis virus A), illustrates this rare syndrome. We present a general review of the pediatric cases reported in the literature.

Child↗
PubMed2005

A geological history of reflecting optics.

Optical reflectors in animals are diverse and ancient. The first image-forming eye appeared around 543 million years ago. This introduced vision as a selection pressure in the evolution of animals, and consequently the evolution of adapted optical devices. The earliest known optical reflectors--diffraction gratings--are 515 Myr old. The subsequent fossil record preserves multilayer reflectors, including liquid crystals and mirrors, 'white' and 'blue' scattering structures, antireflective surfaces and the very latest addition to optical physics--photonic crystals. The aim of this article is to reveal the diversity of reflecting optics in nature, introducing the first appearance of some reflector types as they appear in the fossil record as it stands (which includes many new records) and backdating others in geological time through evolutionary analyses. This article also reveals the commercial potential for these optical devices, in terms of lessons from their nano-level designs and the possible emulation of their engineering processes--molecular self-assembly.

Animals↗
PubMed2005

[Devic's optic neuromyelitis and pulmonary tuberculosis].

INTRODUCTION: Optic neuromyelitis or Devic's syndrome is a very rare disease affecting the optic tracts and the spinal cord. Its association with evolving pulmonary tuberculosis has been noted in a handful of case reports. CASE REPORT: The authors reportthe case of a 40 year old patient with evolving pulmonary tuberculosis who experienced bilateral blindness followed by paraplegia and sphincter disturbance. Clinical examination and investigations excluded direct tuberculous involvement of the nervous system or a reaction to antituberculous therapy and Devic's syndrome was diagnosed, based on Wingerchurk's criteria. Following treatment with corticosteroids and antituberculous chemotherapy, the patient recovered normal mobility and sphincter control but remained completely blind. CONCLUSIONS: Throughout this case report, the authors emphasise the rarity of this association and discuss the pathophysiological mechanism, which appears to be an immune dysfunction triggered by mycobacterial infection.

Adult↗
PubMedDate not supplied

[Devic's optic neuromyelitis: analysis of 7 cases].

INTRODUCTION: Devic's optic neuromyelitis is an unusual condition characterized by the association of unilateral or bilateral optic neuritis and myelitis, both of which are relapsing. Prognosis is usually poor, both for the optic nerve and for the spinal medulla which becomes cavitated. This leads to severe handicap and deterioration in quality of life, except in cases presenting as children. PATIENTS AND METHODS: We studied seven cases of this condition and describe their clinical and neuroimaging features, cerebrospinal fluid (CSF), evaluation, complications, prognosis and treatment. This data was compared with that in the literature. RESULTS AND CONCLUSIONS: 1. It is an unusual condition--only 7 cases have been seen at our centre--making up approximately 0.1% of the inflammatory pathology of the spinal cord seen. 2. During the first few hours or days the clinical and radiological findings may not correspond. There may be marked deterioration of CNS function but with normal neuroimaging findings. This may lead to serious problems in diagnosis, which can usually be resolved by repeating the investigation. 3. Differential diagnosis should be made with intramedullary tumors when on neuroimaging there is increased spinal cord diameter with uptake of contrast, and psychiatric disorders when this is normal. 4. The condition usually deteriorates leading to severe disability, since loss of visual acuity is added to the severe spinal cord lesion. 5. Diagnosis should be made by application of the criteria of clinical evolution, imaging and biochemistry defined in the literature, although firm diagnosis can only be made on anatomopathological studies, usually at autopsy.

Adolescent↗
PubMed2002

Active aberration correction for the writing of three-dimensional optical memory devices.

We describe an active optical system that both measures and corrects the aberrations introduced when writing three-dimensional bit-oriented optical memory by a two-photon absorption process. The system uses a ferroelectric liquid-crystal spatial light modulator (FLCSLM) configured as an arbitrary wave-front generator that is reconfigurable at speeds as great as 2.5 kHz. A method of aberration measurement by the FLCSLM wave-front generator is described. The same device is also used to correct the induced aberrations by preshaping the wave fronts with the conjugate phase aberration as well as to scan the focal spot in three dimensions. Experimental results show the correction of both on- and off-axis aberrations, allowing the writing of data at depths as great as 1 mm inside a LiNbO3 crystal.

Journal Article↗
PubMedDate not supplied

[Devic's optic neuromyelitis: presentation as an inflammatory spinal tumour].

INTRODUCTION: Devic s optic neuromyelitis is a clinical syndrome described over 100 years ago and characterized by episodes of severe transverse myelitis, affecting several spinal segments, and simultaneously or otherwise, neuritis of the optic nerve. Both types of disorder may be acute or subacute. In spite of many reviews in recent years, it is still not clear whether it is a distinct clinical entity or whether it is really a form of Multiple Sclerosis. In recent years several authors have drawn up a list of diagnostic criteria to distinguish between Devic s Disease and Multiple Sclerosis. Several aetiologies have been implicated in causing this syndrome, from infectious diseases to demyelinating disorders. However, there is a group of patients who have no associated pathology, in whom it is correct to speak of Devic s Disease. CLINICAL CASE: We studied a patient with a clinical condition compatible with Devic s disease, with an inflammatory tumour in the cervical region, a radiological finding not previously reported. CONCLUSION: When making the diagnosis in patients with inflammatory spinal tumors and no symptoms of demyelination in the rest of the central nervous system, Devic s disease should be borne in mind.

Female↗
PubMed1997

[Devic's optic neuromyelitis. Follow-up of the evolution of the medullary lesions using magnetic resonance].

The nosology of Devic's optic neuromyelitis (NMOD) is controversial. Although classically considered to be a variety of multiple sclerosis, there are a number of differentiating characteristics which would permit classification as a separate condition. The evolution of changes in the medulla, as shown by magnetic resonance, is described in a patient with recurrent episodes of myelitis and optic neuritis. In successive exacerbations widening of the medulla was seen, with the appearance of areas of cavitation which later gave rise to atrophy of the medulla. During an 18 year follow-up period the symptoms were only of visual and medullary pathology, on magnetic resonance no other lesions were found in other parts of the central nervous system. The condition corresponded to Devic's optic neuromyelitis (NMOD). Whether it is a variant type of multiple sclerosis or a distinct entity, NMOD shows differentiating characteristics.

Atrophy↗
PubMed1976

The effect of visual feedback and self-scaling on plaque control behavior.

Psychological factors are involved in inducing patients to practice the plaque control necessary for periodontal health. It is suggested that oral hygiene behavior can be modified by increasing visual feedback by means of optical devices, and by giving patients the task of scaling their own teeth. The optical devices used for intraoral inspection must be specifically designed for this task. A pilot study was undertaken to test the modification in plaque control behavior in patients using a specially-designed optical system and performing self-scaling. Twelve patients participated in the study; six were given optical devices and taught self-scaling and plaque control, whereas the other six acted as controls, received a scaling from a hygienist, and were taught plaque control. All subjects received 3 hours of chairside time. Before treatment both groups had mean PHP indiced (plaque) of 3.2. Five months after the completion of treatment, the experimental group had a mean PHP index of 0.7, whereas the control group had a score of 1.9. The patients performing self-scaling demonstrated that they could remove supragingival calculus and extrinsic stains as effectively as a trained hygienist.

Dental Equipment↗
PubMed2003

All-fiber spot-size transformer for efficient free-space optical interconnecting devices.

A new concatenated configuration of optical fibers is proposed to improve misalignment tolerance and working distance in a free-space optical interconnection. The structure is composed of three segments: a thermally expanded core fiber, a coreless silica fiber, and a claddingless graded-index fiber. A numerical analysis for the design of each fiber segment is performed completely, and the device characteristics are experimentally evaluated in terms of the tolerances for a 1-dB coupling-loss increment against longitudinal, transverse, and angular misalignments.

Journal Article↗
PubMed1999

Systemic lupus erythematosus with optical neuromyelitis (Devic's syndrome). A case with a 35-year follow-up.

Optical neuromyelitis or Devic's syndrome is a very uncommon neurological manifestation of systemic lupus erythematosus. It is also associated with antiphospholipid antibodies, limited responsiveness to glucocorticoid treatment and a poor prognosis. We report the case of a female systemic lupus erythematosus patient who developed recurrent flares of optical neuritis and transverse myelitis. These flares consistently responded to glucocorticoid therapy. Despite the absence of overt anticardiolipin antibodies in the course of the disease, long-term anticoagulant therapy has been introduced with positive results. Treatments are usually of limited efficacy in Devic's syndrome. In our patient, however, aggressive glucocorticoid treatment resulted in prolonged survival.

Adolescent↗
PubMed1998

Tests of a linear model of visual-vestibular interaction using the technique of parameter estimation.

The goal of this study was to test whether a superposition model of smooth-pursuit and vestibuloocular reflex (VOR) eye movements could account for the stability of gaze that subjects show as they view a stationary target, during head rotations at frequencies that correspond to natural movements. Horizontal smooth-pursuit and the VOR were tested using sinusoidal stimuli with frequencies in the range 1.0-3.5 Hz. During head rotation, subjects viewed a stationary target either directly or through an optical device that required eye movements to be approximately twice the amplitude of head movements in order to maintain foveal vision of the target. The gain of compensatory eye movements during viewing through the optical device was generally greater than during direct viewing or during attempted fixation of the remembered target location in darkness. This suggests that visual factors influence the response, even at high frequencies of head rotation. During viewing through the optical device, the gain of compensatory eye movements declined as a function of the frequency of head rotation (P < 0.001) but, at any particular frequency, there was no correlation with peak head velocity 9P > 0.23), peak head acceleration (P > 0.22) or retinal slip speed (P > 0.22). The optimal values of parameters of smooth-pursuit and VOR components of a simple superposition model were estimated in the frequency domain, using the measured responses during head rotation, as each subject viewed the stationary target through the optical device. We then compared the model's prediction of smooth-pursuit gain and phase, at each frequency, with values obtained experimentally. Each subject's pursuit showed lower gain and greater phase lag than the model predicted. Smooth-pursuit performance did not improve significantly if the moving target was a 10 deg x 10 deg Amsler grid, or if sinusoidal oscillation of the target was superimposed on ramp motion. Further, subjects were still able to modulate the gain of compensatory eye movements during pseudo-random head perturbations, making improved predictor performance during visual-vestibular interactions unlikely. We conclude that the increase in gain of eye movements that compensate for head rotations when subjects view, rather than imagine, a stationary target cannot be adequately explained by superposition of VOR and smooth-pursuit signals. Instead, vision may affect VOR performance by determining the context of the behavior.

Adult↗
PubMed1991

Magnetostrictive calibration of a precision optical measurement device for studies of tooth eruption.

In order to calibrate a precision-measuring instrument for studies of tooth eruption, a calibration device capable of repositioning an optical grating in steps accurate to at least 0.02 microns was required. At this level, piezoelectric and similar pushers encounter problems. A new calibration device based on the magnetostrictive properties of nickel was developed. Accuracy better than 0.02 microns was verified by relating its movements to the wavelength of the green line of mercury, and the device was successfully used to calibrate the instrument for establishing tooth position. Magnetostriction offers a way to calibrate precision measurement instruments for other applications.

Bicuspid↗