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At least 271 records · Page 15Linked to original sources
PubMed1990

A magnetic measurement device for the kinematic analysis of unrestrained human hand movements.

A magnetic measurement device is described which was constructed to study human hand- and finger-movements. The system overcomes some problems frequently arising in the study of finger grip movements. It allows the simultaneous recording of several positions which cannot be observed with optical devices because they are hidden by other parts of the limb. Trajectories are recorded using small receiver coils moving in an alternating magnetic field of 3 transmitter coils. The performance of subject's movements is not significantly disturbed. A high sampling rate and a lack of mechanical damping permit a high temporal resolution which can analyze rapid movements. Subjects are not exposed to any biological risk or discomfort. Thus, a recording session can be repeated numerous times. The results obtained from this type of apparatus may allow quantification of the course of progressing diseases and to study the effects of remediation.

Electromagnetic Fields↗
PubMed2005

Beam shaping by use of hybrid acousto-optics with feedback.

We theoretically demonstrate beam shaping through adaptive feedback in an acousto-optic device with electrical feedback by using experimentally determined parameters. Cases of positive feedback and negative feedback from undiffracted and diffracted orders are investigated. In addition, we demonstrate the dependence of the final value of the induced grating strength in the acousto-optic cell on the feedback parameters.

Algorithms↗
PubMedDate not supplied

Subcutaneous capillary filtrate collector for measurement of blood glucose.

The capillary filtrate collector (CFC) is a device that creates an ultrafiltrate at 50-100 microliters/h from subcutaneous capillaries, and carries this filtrate out of the body for chemical analysis. From inside out, components include three looped hollow fiber ultrafiltration membranes, a polytetrafluoroethylene (PTFE) cuff, polyurethane tubing, a "Y" connector leading to a sampling port, a hub, and a needle placed into a 5 ml vacutainer tube. Animal studies have demonstrated that the CFC filtrate glucose level is exactly that of blood at the time the filtrate is created. The authors have performed clinical trials to determine the correlation of blood glucose and CFC glucose levels, and the time delay between contemporary samples. Seven diabetic patients wore the CFC device, tubing, and vacutainer tube for 1 month. In home monitored diabetic patients, fingerstick glucose measurements were performed at the usual daily schedule. The vacutainer was then evacuated, and this average sample analyzed and compared with the average of prior blood glucose levels. An optical device then was applied to measure the linear velocity of CFC fluid through external tubing, and predict the time for fluid to pass from fibers to the sampling port (average, 25 min). Capillary filtrate collector samples drawn at this time had glucose concentrations that generally correlated with blood levels. In diabetic patients on hemodialysis, the vacutainer was evacuated at the start of each treatment, and CFC and blood samples were drawn every 20 min during the treatment. Comparison of glucose-versus-time curves indicated a reasonable correlation between blood and CFC samples, with a delay related to flow rate (which declined 50% during dialysis).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗
PubMedDate not supplied

[Experience in the organization of offices for specific vision correction].

Three new kits of optic devices for the selection of means facilitating orientation in the space, for writing, reading, and other work involving the visual control, and devices that help operate these kits have been developed for rooms organized to correct the vision of poor-sighted patients. Problems of training personnel and rehabilitationologists for work at enterprises for blind people are discussed, as are those concerned with production, use, and realization of optic amplifiers.

Blindness↗
PubMed2001

Spatial confinement of avidin domains in microwell arrays.

Microwell arrays were chemically etched across the distal faces of coherent fiber-optic bundles. A typical 1.6 mm diameter array comprised approximately 3000 individual microwells that were approximately 1-14 microm deep and approximately 22 microm wide. A methodology involving organosilane functionalized microwell surfaces and site-selective photobiotin chemistry was developed to partially fill microwells with a thin avidin layer. Avidin microwell arrays were characterized using charge coupled device optical microscopy and scanning electron microscopy. The avidin microwell arrays had individual well volumes that were six orders of magnitude smaller and up to 30-fold more numerous than commercially available avidin-coated microtiter plates. Preliminary results indicated that individual avidin microwells were ideally suited to house single biological cells. Using standard epifluorescence microscope optics and a mercury-arc lamp, an individual 22 microm wide microwell could be optically addressed and selectively filled with avidin without the use of a photolithographic mask. The ability to control both the size and position of avidin domains on the microwell array surface demonstrates the utility of this methodology towards fabricating a single microwell array with multianalyte sensing capabilities.

Avidin↗
PubMed1959

Nonsurgical treatment of convergent strabismus.

It is generally agreed that surgical treatment of convergent strabismus should be withheld until all other less traumatic approaches have proved ineffectual. There are four categories of nonsurgical treatment. One is psychiatric. Too often psychiatric problems in the causation of convergent strabismus are either overlooked or unrecognized. Another is the proper employment of optical devices. For example, spectacle lenses to eliminate the need for excessive accommodation with its associated convergence excess, and the employment of prisms in the lenses to permit the two eyes to see as a unit even though they may not be properly anatomically oriented. Another kind of treatment is orthoptics, the use of exercises and rather complex optical equipment in a laboratory to train the patient in coordination between the two eyes. Treatment with drugs is based on the fact that certain drugs reduce the effort necessary for accommodation (much as eye-glasses do) and therefore lessen the stimulus toward convergence which may possibly tend toward the development of convergent strabismus.

Accommodation, Ocular↗
PubMed2001

Central corneal thickness measurement with a retinal optical coherence tomography device versus standard ultrasonic pachymetry.

PURPOSE: To demonstrate the capability of a standard, commercially available optical coherence tomography device (originally designed to measure retinal thickness) to image the human cornea in vivo and to measure central corneal thickness (CCT) in normal and edematous corneas. The intrapatient precision and interpatient variability of this novel application was compared to standard ultrasonic pachymetry. Also, the correlation of both methods was investigated. METHODS: CCT measurements using optical coherence tomography (OCT) and ultrasonic pachymetry (PACH) were obtained in 36 normal eyes and 16 eyes with corneal edema. RESULTS: Direct in vivo imaging of the cornea and measurements of CCT by OCT could be performed in all eyes. In normal subjects, CCT(OCT) was 530+/-32 microm and CCT(PACH) was 581+/-34 microm. The two methods showed a highly significant correlation with a standardized regression coefficient of 0.988. The difference between both methods was constant over the range of CCT (mean difference, 49.4+/-5.9 microm). The mean intrapatient SD of CCT measurements was 4.90 microm and 4.96 microm for OCT and PACH, respectively. In patients with corneal edema, mean CCT(OCT) was 601+/-59 microm, and mean CCT(PACH) was 667+/-68 microm. The difference between the two techniques increased slightly with increasing corneal edema (mean difference, 66.9+/-10.9 microm). CONCLUSION: Imaging of the human cornea can be performed by a standard retinal OCT device, and OCT measurement of CCT shows excellent correlation to values obtained by PACH, giving similar readings separated by a constant difference. In corneal edema, the difference between the two methods is additionally increased, but continues to demonstrate excellent consistency.

Adult↗
PubMed2006

Electro-optical microscopy: mapping nonlinear polymer films with micrometric resolution.

The first demonstration, to the best of our knowledge, of electro-optical microscopy is presented and applied to a polymer-based optical device. A confocal transmission microscope with interferometric homodyne detection is implemented to measure Pockels phase shifts with micrometric spatial resolution and an accuracy level down to 4 x 10(-7) rad. This technique is applied to poled polymer films in which noncentrosymmetric molecular orientation is preliminarily achieved in the sample plane between transverse planar electrodes. The electro-optic mapping of this structure exhibits nonuniform and asymmetric patterns of the nonlinear response that are characteristic of the poling spatial inhomogeneity as confirmed by second-harmonic generation microscopy.

Journal Article↗
PubMed2002

Control of the optical band structure of liquid crystal infiltrated inverse opal by a photoinduced nematic-isotropic phase transition.

Recently, photonic band gap (PBG) crystals with lattice parameters comparable to the wavelength of light have attracted much attention, because they offer unique ways in which to control the propagation of light. PBG crystals have applications in laser, quantum optical devices, and so on. For many of these applications, it is important to have the capability of tuning the photonic band structures. The fabrication of such tunable PBG crystals is still a challenge. In this paper, we proposed that switchable PBG crystals could be realized by taking advantage of the phase transition in liquid crystals induced by the photoisomerization of azo dyes. A dynamic change in the optical stop band was demonstrated. Such photoswitchable PBG crystals provide a method by which light can be routed using light.

Journal Article↗
PubMedDate not supplied

Management of the challenging airway with the Bullard laryngoscope.

The Bullard laryngoscope is a rigid fiber-optic device that offers a new approach to oral laryngoscopy. In this report, I present five cases illustrative of the use of the Bullard laryngoscope in patients with demonstrated or suspected difficult laryngoscopy and intubation.

Adult↗
PubMed1991

Sperm motility index: a new parameter for human sperm evaluation.

OBJECTIVE: The study was performed to evaluate the correlation between sperm motility index, a novel parameter of semen quality, and routine semen analysis parameters by microscopic evaluation. DESIGN: Sperm motility index was measured by an electro-optical device, the Sperm Quality Analyzer (United Medical Systems Inc., Santa Ana, CA). Human semen samples covering the whole span of qualities were analyzed prospectively and simultaneously by both methods. SETTING: Samples were collected from patients referred to university hospital infertility clinics. PATIENTS, PARTICIPANTS: Nine hundred sixty-eight semen samples of 812 patients and healthy men were analyzed. MAIN OUTCOME MEASURE(S): Sperm motility index is a measurement of optical density fluctuations caused by motile cells; therefore, a positive correlation was anticipated between its values and semen motility parameters. RESULTS: Sperm motility index values demonstrated statistically significant correlation with motile cell concentration, total cell concentration, and percent motile cells. They were also shown to reliably represent semen quality assessment obtained by two experienced andrologists. CONCLUSIONS: The sperm motility index provides a reliable and objective reflection of semen motility parameters and quality.

Autoanalysis↗
PubMedDate not supplied

Complications associated with cannula insertion techniques used for laparoscopy in standing horses.

OBJECTIVE: To report our experience and complications associated with different cannula insertion techniques for laparoscopy in standing horses. STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Forty horses that had laparoscopy for diagnostic or surgical purposes. METHODS: After a physical examination, including rectal palpation, standing laparoscopy was performed in 40 sedated horses. Local anesthetic was injected at each site of cannula insertion in the left flank. Horses were divided into 5 groups: Pneumoperitoneum was induced before cannula insertion using a Verres needle (group 1, n = 3) or a 12-g catheter (group 2, n = 14); the cannula was inserted before inducing a pneumoperitoneum (group 3, n = 9); the cannula was inserted under visual control, using an operating laparoscope (group 4, n = 2) or a Visiport Optical Trocar (group 5, n = 12). Horses were observed for 7 days. RESULTS: Problems with insufflation or cannula insertion occurred in 12 horses: 6 had peritoneal detachment, 4 had a splenic puncture, and 2 had descending colon puncture. Eleven of these complications occurred in groups 1 to 3 and only 1 in groups 4 and 5. CONCLUSIONS: The Visiport optical device allows controlled insertion of the initial trocar, and thus avoided potential problems associated with "blind" cannula insertion techniques and was used effectively in horses that had feed withheld for 12 hours. This technique enables direct insertion of a cannula directly into the right flank. CLINICAL RELEVANCE: Complications associated with initial cannula insertion in the paralumbar fossa, for laparoscopy, in standing horses can be minimized with the use of an optical cannula.

Anesthetics, Local↗
PubMedDate not supplied

Comparison of low-vision reading with spectacle-mounted magnifiers.

Reading is the most common goal among persons with age-related macular degeneration and other retinal diseases that lead to macular loss, as well as the functional task most affected by the resulting central scotomas. This project determined whether reading ability is different when persons with macular loss read with a new hybrid-diffractive spectacle magnifier versus a refractive-aspheric spectacle magnifier and an aplanatic spectacle magnifier. After subjects completed a low-vision examination, we assigned them to groups that compared different types of spectacle magnifiers and assessed their reading acuity, speed, critical print size (print size large enough to provide a subject's best fluent reading), accuracy, and comprehension. Subjects completed visual analog scales to indicate their perceptions of satisfaction with reading, comfort with reading, and cosmesis (comfort with allowing others to see them read) and were asked which of the compared spectacle magnifiers they preferred for prescription. We subjected the data to paired t-tests to ascertain whether differences existed in subjects' reading ability and perceptions between the types of reading devices. Subjects' reading comprehension, perception of satisfaction, and perception of cosmesis were significantly better with the hybrid-diffractive lens than with the refractive-aspheric lens. Although subjects' critical print size was significantly better with the aplanatic lens than with the hybrid-diffractive lens, functional reading ability was not significantly different. More subjects preferred the hybrid-diffractive lenses for prescription. The hybrid-diffractive spectacle magnifiers are an important addition to the optical-device armamentarium for reading with low vision.

Aged↗
PubMed2006

Proton-exchanged 36 degrees Y-X LiTaO3 waveguides for surface acoustic wave.

A nontoxic proton source, octanoic acid, was adopted to fabricate proton-exchanged (PE) waveguides in 36 degrees Y-X lithium tantalate (LiTaO3) substrates. The PE ability of octanoic acid on LiTaO3, the penetration depth, was investigated by secondary-ion mass spectrometry (SIMS). The penetration depth of hydrogen ion exhibited an obviously step-like profile, which will be excellent for waveguide application. The relationship between waveguide depth (d) and exchanging time (t) was represented by d = 0.0653 X square root of t at T = 200 degrees C. To deserve to be mentioned, the octanoic acid has a slight dissociation coefficient and low activation energy, thus the accurate waveguide depth control can be obtained. For the application of acoustic wave guided acousto-optic devices, the leaky surface acoustic wave (LSAW) properties of PE 36 degrees Y-X LiTaO3 waveguides were investigated. The phase velocity slightly decreased with the increase of kd, where k was wavenumber. An indispensable parameter of acoustic wave device, the temperature coefficient of frequency (TCF), calculated from the frequency change of the output of LSAW delay line showed an increase with increased kd.

Energy Transfer↗
PubMed1984

[Pulfrich phenomenon].

A physiological and clinical study of the Pulfrich stereo-phenomenon was performed. The most important physiological parameters are object movements, luminous factors, and the position and movement of the eyes. Our experimental research emphasizes the retinal illumination factors, modified by many optical devices (pinhole, stenopeic slit, etc.); the paradoxical perceptive aspects of the Pulfrich phenomenon; and, above all, outlines the negligible role of the metric factors. The Pulfrich phenomenon is mainly time-dependent, and is defined as a stereoscopic illusion related to the temporal disparity between the visual input arising from the two eyes at the time of their cortical integration. In ocular pathology, 267 subjects were studied, the ocular abnormalities being divided into diseases of the pupil, cornea and vitreous body, cataracts, retina, optic nerve, glaucoma and strabismus. The difference between the spontaneous Pulfrich phenomenon and the provoked Pulfrich phenomenon is stressed: the spontaneous Pulfrich phenomenon is rare (14% of subjects); by itself it is anomalous and is a functional symptom his mechanism may vary according to the etiology; on the contrary, the provoked Pulfrich phenomenon is a normal phenomenon, induced by a filter in front of one eye; its absence is pathological either with the filter in front of the better eye, the bad eye, or of each in turn. In clinical practice this lack is frequent (46% of subjects), and is related to an alteration of binocular vision, but without etiological specificity.

Depth Perception↗
PubMed2005

Pericardial exploration by pericardioscopy during a surgical sub xyphoid approach.

This clinical feasibility study was planned to evaluate pericardioscopy as a means of control of the pericardial cavity during drainage for pericardial effusion by a surgical sub xyphoid approach. Seventeen patients who underwent an operation for surgical drainage of the pericardium (11 medical and 6 postoperative pericardial effusions) benefited from a pericardial exploration with a mediastinoscope or rigid thoracoscope (Karl Storz, Germany). In 7 of the 11 medical cases, a severe inflammation of the pericardium associated with false membranes was visualized; in 3 cases, the pericardium was considered as normal; and in 1 case, pericardial metastases were visualized. In the 6 postoperative cases, clots were visualized with a venous bypass graft and the pulmonary cannula of a right ventricular assist device (Thoratec, USA) was also perfectly controlled. The cause of bleeding was reported in one case and suspected in another, but required total sternotomy for repair in both cases. No mortality or morbidity was reported to be directly due to the technique. The peroperative assessment of pericardial cavity is possible by use of pericardioscopy with a satisfactory resolution, but visualization of the left lateral part of the heart remains difficult. The possibility exists to partially remove clots and false membranes, obtain various samples, and control the position of the drains. Improvement in the optic device with the possibility of a flexible device that has a tip protector for optimal visualization, may improve both the technique and results.

Endoscopy↗
PubMed2005

Formulation of a Mueller matrix for modeling of depolarization and scattering of nitrobenzene in a Kerr cell.

We have studied the depolarization of light from nitrobenzene in a Kerr cell. We observed that absorption in nitrobenzene is electric-field dependent. For modeling a nitrobenzene device we formulated a Mueller matrix for the Kerr-cell assembly, and by operating it on a Stokes vector of the input light we obtained a corresponding Stokes vector for the output light. The first parameter of the output Stokes vector corresponds to the intensity transmittance. It was simulated and compared with the measured intensity transmittance for several orientations of the polarizer-analyzer pair with respect to the applied voltages. The measurement of all unknown coefficients in a Mueller matrix consisting of the superposition of nondepolarizing and depolarizing components predicts the depolarization, scattering, and absorption in the nitrobenzene electro-optic device. The output intensities of the orthogonally polarized and cross-coupled depolarizing coefficients are in good agreement for a semi-isotropic medium. The formulated Mueller matrix agrees with the experimentally measured transmittance.

Journal Article↗
PubMed2004

Phase plate to extend the depth of field of incoherent hybrid imaging systems.

A hybrid imaging system combines a modified optical imaging system and a digital postprocessing step. We describe a spatial-domain method for designing a pupil phase plate to extend the depth of field of an incoherent hybrid imaging system with a rectangular aperture. We use this method to obtain a pupil phase plate to extend the depth of field, which we refer to as a logarithmic phase plate. Introducing a logarithmic phase plate at the exit pupil of a simulated diffraction-limited system and digitally processing the detector's output extend the depth of field by an order of magnitude more than the Hopkins defocus criterion. We also examine the effect of using a charge-coupled device optical detector, instead of an ideal optical detector, on the extension of the depth of field. Finally, we compare the performance of the logarithmic phase plate with that of a cubic phase plate in extending the depth of field of a hybrid imaging system with a rectangular aperture.

Journal Article↗