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At least 739 records · Page 41Linked to original sources
PubMed1988

Usefulness of computerized visual acuity testing in a pediatric ophthalmology clinic.

We investigated the usefulness of a computerized illiterate-E-style acuity test in 111 children ranging in age from 3 to 13 (mean 6.56) years consecutively referred to a large pediatric ophthalmology clinic. Visual acuity was measured in both eyes of each subject by means of conventional testing with an optical projection device and computerized testing with a program run on a microcomputer. Of the 222 eyes 155 (70%) showed no difference in visual acuity between the two procedures. A difference of one acuity line was found for 63 eyes (28%), and a difference of two lines was found for 4 eyes (2%). The conventional test yielded a higher acuity score in 75% of the cases in which a one-line difference was found and 50% of those in which a two-line difference was found. Our results indicate that computerized testing is a valid and effective method of assessing visual acuity in children.

Adolescent↗
PubMed1988

[Quantifying the stimulus parameters in the neck torsion test].

Cervically induced eye movements can be observed when the trunk is rotated and the head fixed. In most test situations, rotating chair motion and head fixation are carried out manually. As a result, specific and non-specific sources of error are involved in these procedures that hamper the reproducibility of test conditions. A system is described that provides quantifiable and reproducible, electronically controlled movements of the rotating chair. Ramp and rectangular stimulus profiles are achieved by infrared optical gate devices on the chair axis. Various processor-controlled sequences of angular displacement and duration can be programmed and monitoring of chair movement is available to the operator during testing, which is otherwise performed in complete darkness. Individual casts of the upper jaw connected with a telescope wall clamp facilitate optimal head fixation. Since great caution is required when using an electronically controlled chair for such tests, and the possibility of damage to the vertebral column is increased by head fixation, several devices have been incorporated into the equipment to fulfil safety requirements such as release mechanism in the head fixation system, besides other safety devices. This system enables cervically induced eye movements which can be related to amplitude, acceleration and velocity of trunk rotation. The results are important for direction and extent of eye shifts, nystagmus and circular-vection.

Fixation, Ocular↗
PubMed1983

[2-dimensional ultrasonic scanning for irradiation planning].

The paper is concerned with the results of the utilization of echotomography in the topometric preparation of patients with malignant tumors for irradiation. Proceeding from the examination of 600 cancer patients in the All-Union Cancer Research Center. USSR AMS, it has been established that echotomography makes it possible not only to define the borders of pathology in the peritoneal cavity and retroperitoneal space but also to specify the relative position of the adjacent internal organs. Some practical aspects of the use of ultrasound for topometry are discussed. A possibility of using this method for the three-dimensional planning of irradiation is indicated. Using an echotomoscope one can obtain a contour of the section of a soft phantom with an accuracy of 5 +/- 1 mm that significantly exceeds the limits of precision of a contour measured with the help of a lead band where it equals 10 +/- 7 mm. Echotomography makes it possible to get a contour in any plane. In view of certain limitations of the echotomographic method one should also resort to x-ray methods for the topometric planning of irradiation to specify the position and size of the bearing osseous structures. While converting reduced ultrasound images in the scale of 1:1 the optic method with an episcope proved to be the most accurate one where an error of reproducibility of a contour reaches 1 mm. In the use of an optical-electronic device this value exceeds 10 mm and corresponds to 4 mm while utilizing a pantograph.

Humans↗
PubMed1995

Effects of time of day on self-paced performances of prolonged exercise.

Pre-exercise body temperature varies throughout the day due to its circadian rhythm. This study aimed to compared responses to sustained exercise in the morning and in evening. Rectal temperature was measured pre-exercise and throughout a 60 min test on a cycle ergometer against a fixed frictional resistance in seven males (aged 19-24 years). The subjects were instructed to work as hard as possible over the entire exercise period but could vary the pedal frequency at any time. Power output was calculated by computer, utilising an optical detection device to monitor flywheel revolutions. Tests were performed at 08:30 and 17:30 h, balanced for order with at least 72 hours between tests. Rectal temperature was lower pre-exercise in the morning (37.2 degrees C) than at evening (37.8 degrees C). This differences was reduced to 0.3 degrees C by the end of exercise. Mean power output was similar for the two times of day for the whole exercise period. A higher power output in the evening over the first half of the test was compensated for by a greater performance in the morning over the second 30 min (p < 0.05). It seems that the pacing of endurance performance is affected in the morning, but without any overall effect at least for the duration examined and at the ambient environmental temperature of 17-19 degrees C.

Adult↗
PubMed1997

[Laser thermocoagulation of adenoma of the prostate using an interstitial approach].

Interstitial laser coagulation (ILC) is a minimally invasive treatment for benign prostatic hyperplasia (BPH). The objective of ILC is to induce shrinking of the prostate while preserving all surrounding tissues. To achieve thermal coagulation well inside the adenoma, not at its urethral surface, laser radiation of a Nd:YAG laser or a diode laser is transmitted by specially designed laser fibers repeatedly placed in the prostate tissue. This results in secondary atrophy and regression of the prostate lobes, not sloughing of necrotic tissue. Since, July 1991, more than 800 patients have been treated in several studies. Based on initial experiences, many technical and procedural improvements of ILC have been introduced for clinical use, such as advanced radiation programs and new application devices including optical feedback systems. Imaging studies demonstrated treatment effects and allowed further treatment optimization. Clinical studies have demonstrated the safety and efficacy of ILC. This review summarizes several articles published on ILC and reports initial results of ongoing studies comparing ILC and transurethral resection of the prostate (TURP).

Aluminum Silicates↗
PubMed1996

Optical breast lesion localization fiber: preclinical testing of a new device.

Preclinical testing was performed of an optical breast lesion localization fiber to guide surgical excision. The prototype device comprised dual 0.010- inch (0.254-mm)-diameter hooks attached to the tip of a 1,000-microns (0.03937-inch)-diameter optical fiber, which allowed retention in soft tissue after passage through a 17-gauge extra-thin-wall needle. The proximal end of the optical fiber was attached to a 15-mW, 635-nm diode laser, with a thumbscrew connector. The tip of the optical fiber was visible through several centimeters of breast tissue in two human mastectomy specimens, which facilitated determination of the location of the hooks. The optical localization fiber may allow lesions to be approached at surgery by many different paths. Clinical tests are indicated to further evaluate this device.

Breast↗
PubMed2002

Low-loss ultrabroadband 90 degree optical rotator with collinear input and output beams.

An achromatic device to rotate optical polarization by 90 degrees is described. This is based on a series of reflecting surfaces that rotates incoming light about the optical axis and translates it such that the exiting light is collinear. Polarization rotation is achieved by rotation of the optical beam, as opposed to the more common approach of phase retardation by use of birefringent elements. For broadband operation from the UV to the near infrared, the device was constructed by use of total internal reflection in three fused-silica glass components. Losses are minimized with interstitial surfaces designed to be angled close to Brewster's angle.

Journal Article↗
PubMed2006

A silicon retina that reproduces signals in the optic nerve.

Prosthetic devices may someday be used to treat lesions of the central nervous system. Similar to neural circuits, these prosthetic devices should adapt their properties over time, independent of external control. Here we describe an artificial retina, constructed in silicon using single-transistor synaptic primitives, with two forms of locally controlled adaptation: luminance adaptation and contrast gain control. Both forms of adaptation rely on local modulation of synaptic strength, thus meeting the criteria of internal control. Our device is the first to reproduce the responses of the four major ganglion cell types that drive visual cortex, producing 3600 spiking outputs in total. We demonstrate how the responses of our device's ganglion cells compare to those measured from the mammalian retina. Replicating the retina's synaptic organization in our chip made it possible to perform these computations using a hundred times less energy than a microprocessor-and to match the mammalian retina in size and weight. With this level of efficiency and autonomy, it is now possible to develop fully implantable intraocular prostheses.

Algorithms↗
PubMed2005

Automation of liquid-liquid extraction-spectrophotometry using prolonged pseudo-liquid drops and handheld CCD for speciation of Cr(VI) and Cr(III) in water samples.

A simple spectrophotometric system, based on a prolonged pseudo-liquid drop device as an optical cell and a handheld charge coupled device (CCD) as a detector, was constructed for automatic liquid-liquid extraction and spectrophotometric speciation of trace Cr(VI) and Cr(III) in water samples. A tungsten halogen lamp was used as the light source, and a laboratory-constructed T-tube with two open ends was used to form the prolonged pseudo-liquid drop inside the tube. In the medium of perchloric acid solution, Cr(VI) reacted with 1,5-diphenylcarbazide (DPC); the formed complex was automatically extracted into n-pentanol, with a preconcentration ratio of about 5. The organic phase with extracted chromium complex was then pumped through the optical cell for absorbance measurement at 548 nm. Under optimal conditions, the calibration curve was linear in the range of 7.5 - 350 microg L(-1), with a correlation coefficient of 0.9993. The limit of detection (3sigma) was 7.5 microg L(-1). That Cr(III) species cannot react with DPC, but can be oxidized to Cr(VI) prior to determination, is the basis of the speciation analysis. The proposed speciation analysis was sensitive, yet simple, labor-effective, and cost-effective. It has been preliminarily applied for the speciation of Cr(VI) and Cr(III) in spiked river and tap water samples. It can also be used for other automatic liquid-liquid extraction-spectrophotometric determinations.

Automation↗
PubMed2006

Self-aligned spatial filtering using laser optical tweezers.

We present an optical spatial filtering device that has been integrated into a microfluidic system and whose motion and alignment is controlled using a laser optical tweezer. The lithographically patterned micro-optical spatial filter device filters out higher frequency additive noise components by automatically aligning itself in three dimensions to the focus of the laser beam. This self-alignment capability is achieved through the attachment of a refractive optical element directly over the circular aperture or pinhole of the spatial filter. A discussion of two different spatial filter designs is presented along with experimental results that demonstrate the effectiveness of the self-aligned micro-optic spatial filter.

Equipment Design↗
PubMed2003

Recent developments in compact ultrafast lasers.

Ultrafast lasers, which generate optical pulses in the picosecond and femtosecond range, have progressed over the past decade from complicated and specialized laboratory systems to compact, reliable instruments. Semiconductor lasers for optical pumping and fast optical saturable absorbers, based on either semiconductor devices or the optical nonlinear Kerr effect, have dramatically improved these lasers and opened up new frontiers for applications with extremely short temporal resolution (much smaller than 10 fs), extremely high peak optical intensities (greater than 10 TW/cm2) and extremely fast pulse repetition rates (greater than 100 GHz).

Journal Article↗
PubMed2007

Phase error corrected 4-bit true time delay module using a cascaded 2 x 2 polymer waveguide switch array.

A fully integrated 4-bit true time delay device using polymer optical switches and waveguide delay lines is demonstrated. The fabricated device, which contains five 2x2 thermo-optic switches, has a maximum power consumption of 143 mW and a switching time less than 3 ms. The rf phase error, which is affected by the optical switch cross talk, is also theoretically analyzed and proved to be negligible by experimental results.

Journal Article↗
PubMed2000

[Devic's neuromyelitis optica. A childhood case and review of the literature].

Neuromyelitis optical (NMO) or Devic's disease is an uncommon clinical syndrome associating unilateral or bilateral optic neuritis and transverse myelitis within about 8 weeks. Usually reported in adults, childhood cases constitute a distinctive clinical entity with good visual and neurological prognosis without long-term recurrence or sequelae. The pathogenesis is explained by autoimmune demyelinization triggered by a viral disease. Some authors suggest an infectious cause. The CT scan is usually negative while MRI shows nonspecific small foci in the white matter. Unlike multiple sclerosis, the main differential diagnosis, in NMO the cerebrospinal fluid may show pleocytosis with elevated protein level without an oligoclonal band. We report a case of neuromyelitis optica occurring in a 4-year-old child following a flu-like syndrome. Clinical outcome was favorable with a short course of high-dose corticosteroids.

Adrenal Cortex Hormones↗
PubMed2001

Microfluidic device for airborne BTEX detection.

We fabricated a microfluidic device for the optical detection of airborne benzene, toluene, ethylbenzene and xylenes (BTEX). The device consists of concentration and detection cells formed of 3 cm x 1 cm Pyrex plates. The concentration cell is composed of an adsorbent to concentrate the BTEX gases and a thin-film heater todesorb the concentrated gases from the adsorbent thermally. The collected gases are introduced into the detection cell, which is connected to optical fibers, to measure their absorption spectra. We optimized the device's operating conditions by studying the thermal characteristics of the concentration cell and the time profile of the gas concentration flowing in the detection cell. We used the device under optimized operating conditions to detect toluene gas as a typical example BTEX. The gas concentration amplification rate was approximately 2 orders of magnitude, and we successfully measured parts-per-million levels of toluene gas with this device.

Air Pollutants↗
PubMed2004

Illumination, optics, and clinical performance of a hand-held magnified visual inspection device (AviScope): a comparison with colposcopy.

OBJECTIVE: Colposcopy is the reference standard for a visual inspection device in terms of illumination, optics, and clinical performance. A hand-held magnification device such as the AviScope, developed as an alternative to naked eye visual inspection with acetic acid, is also of interest as a low-cost, more portable alternative to a colposcope in low-resource settings within the context of cervical cancer prevention programs and for microbicides research. DESIGN: A performance comparison of the AviScope, visual inspection with acetic acid, and three colposcopes. METHODS: An analysis was carried out of the optics and illumination of the colposcopes and the AviScope prototype and of the evidence for the reproducibility and clinical accuracy of visual methods for histologically confirmed high-grade cervical intraepithelial neoplasia. Using the findings, the feasibility of increasing the performance and reducing the cost of a hand-held scope was examined. RESULTS: Published studies have found the AviScope to have slightly higher sensitivity than visual inspection with acetic acid (60.7 versus 55.7%, P < 0.05) without loss of specificity. Despite the variability among the colposcopes, the field of view, resolution, depth of field, magnification, and quality of the illumination beam pattern and spectral output exceeded that of the AviScope. The clinical sensitivity and specificity of colposcopy were higher than that of the AviScope. The availability of improved materials for optics and illumination suggests that a hand-held scope with enhanced performance is feasible. CONCLUSION: Although the performance of the AviScope prototype was suboptimal compared with the colposcopes, it appears possible to design a hand-held magnification device at a reasonable price with better optics and illumination.

Colposcopes↗
PubMed2006

A simple light-emitted diode-induced fluorescence detector using optical fibers and a charged coupled device for direct and indirect capillary electrophoresis methods.

We constructed a simple fluorescence detector for both direct and indirect CE methods using a blue light-emitted diode (470 nm) as excitation source, a bifurcated optical fiber as a waveguide, and a CCD camera as a detector. The connection of all the components is fairly easy even for nonexperts and the use of a CCD camera improves the applicability of this detector compared to the others using PMTs because it permits the recording of 2-D electropherograms or phosphorescence measurements. This detector provides a compact, low cost, and rapid system for the determination of native fluorescence compounds which have high quantum yields by CE with direct fluorescence detection, showing an LOD of 2.6 x 10(-6) M for fluorescein; the determination of fluorescence derivative compounds by CE with direct fluorescence detection, showing an LOD of 1.6 x 10(-7) M for FITC-labeled 1,6-diaminohexane; and nonfluorescence compounds by CE with indirect fluorescence detection with an LOD of 2.7 x 10(-6) M for gallic acid.

Electrophoresis, Capillary↗
PubMed2003

Linear and nonlinear optical properties of ZnGeP2 crystal for infrared laser device applications: revisited.

Measurement of refractive indices in the spectral bands 9-11 microm and 1.32 microm from a cw CO2 laser and a Q-switched Nd:YAG laser, respectively, is reported in a ZnGeP2 crystal. A new set of Sellmeier dispersion relations has been derived from the measured refractive indices data in this crystal. Second-harmonic generation (SHG) of CO2 laser radiation in this crystal is also reported. It is also seen that the previously reported phase-matching data for others experiments in SHG and optical parametric devices is explained satisfactorily with this new set of Sellmeier dispersion relation.

Journal Article↗