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Results for “Optical Devices”

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At least 721 records · Page 40Linked to original sources
PubMed1992

[The adverse effects of local anesthetics on the eye in the development of ocular irritation test].

Referring to the ocular damage produced by local anaesthetics applied to the eye, the authors suggest the use of a test, to reveal the danger that some ophthalmic preparations may represent for patients. They review the studies devoted to the evaluation of ocular damage, particularly those which resulted into tests based on the methodology of Draize. A test scaled down to the mouse eye is described, in which the subjective appreciation is completed by an objective measurement. The test is based on the increased permeability of injured cornea for fluorescein. The fluorescence emitted by this tracer depends on the extent of the micro-lesions and is measured with an optical electronic device. The possibilities and limitations of this test are determined by the relationship between dose and extent of ocular damage. Such a relationship has been established for oxybuprocain. An appropriate concentration of this local anaesthetic allows to investigate the influence of adjuvants, preservatives and viscosifiers on the effect of oxybuprocain on the cornea. The authors conclude that it is possible to apply this test to the development of well-tolerated ophthalmic preparations.

Anesthetics, Local↗
PubMedDate not supplied

[Our experience with treatment of varicocele in a day-surgery protocol].

In the last few years the increasing interest for non-invasive operating techniques has allowed to reevaluate the sublinguinal varicocelectomy surgical technique for idiopathic varicocele surgical treatment. During the years 1998-2001, 29 patients have been operated on sub-inguinal varicocelectomy (14 patients were suffering from idiopathic varicocele of third grade, 11 of second grade, 3 of first grade, and 1 subclinical). Out of the 29 patients, only 10 were unable to procreate. All patients were operated under local anesthesia and discharged the same day (day-surgery). Owing to Authors' experience, the sublinguinal varicocelectomy by optical magnifying devices represents the "gold standard" in the idiopathic varicocele treatment because it allows to minimize relapsing rates, to limit post-operation complications, to improve the reproductive faculty of seminal fluid both qualitatively and quantitatively, to cut patient's operating costs significantly, to keep the operation time within acceptable limits, and to be easily learned and carried out.

Adult↗
PubMed2004

[Measurements of diffusion reflectance and transmittance of biological tissues by using CCD].

The CCD experimental setup and the CCD image analysis system that were developed by using C Language were presented, and the spatially resolved diffusion reflectance and transmittance of porcine muscle and fat were determined by using CCD experimental setup. The experimental results were compared with those of Monte Carlo simulations and those of the two models based on diffusion theory, and we found good agreement between theory and experiment for the range from the beam center to 12 mm. It i s shown that the CCD experimental setup and the CCD image analysis system can be used to measure the spatially resolved diffusion reflectance and transmittance of biological tissues, and this work offers the experimental bases for noninvasive and fast measurement of optical parameters of biological tissues.

Algorithms↗
PubMed2004

[Double light beam multi-channel analysis for laser induced fluorescence spectroscopy].

The incident pulse intensity wave will cause the induced fluorescence wave, which will lead to the obvious error of experiment results. A double-light-beam correlation method between the incident laser and the fluorescence was used to decrease such error efficiently in the experiments. A good correlation factor over 0.9 was obtained by the method in the experiment of R6G fluorescence enhanced by SDS. The method is better than sampling-averaging method when the incident laser intensity has more waves.

Fluorescence↗
PubMed2005

[Optical detection system for micro biochemical analyses].

For the need of biochemical chip, which consumes fewer specimens and is easy to integrate with micro-fluid chip, two kinds of spectrophotometric analysis methods are described in the present paper. Both the direct detection method and evanescent wave detection method are used in the experiments with visible light (460-800 nm). The experimental results proved that the direct detection is simple and evident; on the other hand the evanescent wave detection method consumes much less reagent and is easy to integrate with microchips.

Microfluidic Analytical Techniques↗
PubMed2005

[Analysis of spectral properties of novel holographic transmission notch filter].

Optical filter has extremely important applications in spectroscopy, optical measurement and laser physics. Holographic filter, especially the transmission volume holographic notch filters using dichromate gelatin (DCG), is a new kind of filter with the main characteristic of a very narrow bandwidth. In this paper, measurements were carried out on the spectral properties of this transmission volume holographic notch DCG filter using an ultraviolet-visible transmittance spectrometer. The experimental results show that the relative transmittance of main spectrum of this filter is less than 2% in the visible region between 400 and 800 nm, and the relative transmittance of other spectra are more than 85%. Moreover, the filter has a narrow bandwidth with a half-bandwidth less than 12 nm, and a 1/10 width of the bandwidth less than 15 nm. These results indicate that this new kind of filter has an excellent filter characteristic to the main spectrum of Ar+ laser at the wavelength of 514.5 nm.

Holography↗
PubMed2006

[Surface enhanced Raman scattering spectra of carbozole and azobenzene disperse red polymer].

Surface enhanced resonance Raman scattering (SERRS) was employed to study the molecule alignment of carbozole and azobenzene disperse red polymer on the surface of rough silver thin film. According to the selection rule of optical transitions and experiment results, it was found that the surface geometry of carbozole and azobenzene disperse red polymer was: this was physical adsorption between the carbazole group, which is from the monomer of carbazole and nitro-group which is from the monomer of azobenzene on the surface of rough silver film, and there is almost no interaction between the principal chain and the substrate because of the distance. This geometrical configuration of CAP on the surface of the substrate was proposed to damage the stabilities and efficiency of azobenzene derivatives based optical storage devices.

English Abstract↗
PubMed2007

Influence of impression material and time on the 3-dimensional accuracy of implant impressions.

OBJECTIVE: To investigate, in vitro, the effect of time on the 3-dimensional accuracy of open-tray implant impression copings made of polyvinyl siloxane and polyether impression materials. METHOD AND MATERIALS: Reference models with 4 internal connection implants were fabricated. Four sets of 71 direct impressions were made with square impression copings using an open-tray technique. One set of impressions was made with polyether material (material A) and each of 3 polyvinyl siloxane materials (materials B, C, and D). Three-dimensional changes in spatial orientation of the implant analogs were measured over 48 hours using an optical measurement device. Deviation values were summed over 4 points and averaged per impression. Global differences were tested with a nonparametric Kruskal-Wallis test followed by pairwise comparisons using the Mann-Whitney U test. RESULTS: The mean dimensional accuracy of implant impressions significantly differed over time (P < .001). Materials A and B were found to produce comparable results, For materials C and D there was a significant increase in deviations, with a maximum increase at 2 hours. Deviations for material C were comparable to materials A and B at 48 hours. Baseline values were not maintained by any material. CONCLUSIONS: Within the limits of this in vitro study, it can be concluded that time cannot be neglected as a factor affecting the accuracy of implant master casts.

Dental Implants↗
PubMed1991

Physiology of aging and its influence on the contact lens prescription.

The normal progressive physiological and visual effects of aging and its influence on the ability of contact lenses to provide ametropic correction is examined in this article. Of primary significance is the aging eye's perceptual ability especially in the mesopic range of vision. In addition, a recap of current available techniques is included for correction of presbyopia with contact lenses from the perspective of prescribing for an aging patient--not merely a patient who has lost only the ability to accommodate. One of the hallmarks of the profession of optometry has been its traditional support of the premise that patients should be provided with the best possible optical correction. While there are presbyopic patients who can achieve satisfactory vision via the contact lens modalities now in use, the physiological influences discussed here have been generally ignored by the profession. A redefinition of the criteria indicating patient "success" has evolved from achieving satisfaction through excellent vision derived from the optimum optical correction, to satisfaction obtained through patient selection and indoctrination to wear an optically inferior device. Unless the physiological, visual, and psychological effects of aging are adequately compensated by future contact lens designs, most elderly patients will remain likely to return to spectacles as the deficiencies of contact lens correction become progressively more apparent to them.

Accommodation, Ocular↗
PubMed1991

Speech-perception aids for hearing-impaired people: current status and needed research. Working Group on Communication Aids for the Hearing-Impaired.

Both the overall aging of the population and its exposure to higher noise levels have increased the tendency to hearing loss and the importance of improved hearing aids for speech perception. This article reviews improvements in conventional electroacoustic hearing aids, as well as recently developed alternative classes of speech-perception aids, including surgically implanted cochlear stimulators, and vibrotactile, electrocutaneous and optical stimulating devices. It is concluded that the most effective aid for the vast majority of hearing-impaired persons is, and will remain for the immediate future, the electroacoustic hearing aid. In those cases for which no benefit is demonstrated for the electroacoustic aid, generally meaning persons with profound hearing loss, either the cochlear implant or a tactile aid may provide some improvement in the understanding of speech. In rare cases, some speech understanding in the absence of lip reading is achieved by patients with cochlear implants, for unexplained reasons. This and other pressing questions about speech processing need to be addressed by the research community if more effective aids are to be developed for the use of the 36.5 million hearing-impaired persons expected in the U.S. by the year 2050.

Aged↗