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PubMedDate not supplied

[A computer system for the analysis of television images as a new objective clinical method for assessing the status of the crystalline lens].

The aim of study was the development of a diagnostic device for the determination and analysis of the optic densities of various lenticular laminae on the basis of computer-aided system for analysis of TV images (CASATI). The potentialities of the developed system were evaluated in examinations of 57 diabetics, aged 27 to 78, with opacities beneath the posterior capsule and in the cortical layers of the lens. The reference group consisted of 48 normal subjects without noticeable lens opacities, aged 23 to 76. Comparative densitometry of the lens was carried out in the same patients by reproductive microdensitometry and CASATI. The new method permitted an objective assessment of the optic densities of various layers of the lens and may be used to predict the development of opacities therein. Another possible application of this method is the assessment of the conjunctival vessels status and prediction of the course of various diseases and monitoring the efficacy of therapy thereof.

Adult↗
PubMed2001

Excitability of a semiconductor laser by a two-mode homoclinic bifurcation.

We report on the preparation of optical excitability in a distributed feedback semiconductor laser. The device integrates a single-mode laser and a 250 microm long passive section with cleaved facet. The phase of the light fed back from the passive section is tunable by current. The theoretical analysis shows an ultimate hop between external cavity modes within every phase cycle that is associated with a two-mode homoclinic bifurcation close to which the system becomes excitable. This excitability is clearly demonstrated in the experimental response to optical injection comparing well with simulation calculations.

Journal Article↗
PubMedDate not supplied

Feedback-controlled laser-mediated cartilage reshaping.

OBJECTIVE: To demonstrate feedback-controlled laser-mediated cartilage reshaping using dynamic measurements of tissue optical properties and radiometric surface temperatures. DESIGN: Flat cartilage specimens were reshaped into curved configurations using a feedback-controlled laser device. MATERIALS: Fresh porcine nasal septum, stripped of perichondrium and cut into uniform strips (25 x 10 x 1.5-2.1 mm) with a custom guillotine microtome. INTERVENTIONS: Cartilage specimens secured in a cylindrical reshaping jig (2.5 cm in diameter) and irradiated with an Nd:YAG laser (lambda = 1.32 microns, 25 W/cm2, 50-Hz pulse repetition rate). During laser irradiation, radiometric surface temperature was measured along with changes in forward-scattered light from a diode probe laser (lambda = 650 nm, 5 mW), using a lock-in detection technique. Sequential irradiation of the specimen outer surface was made (3 laser passes). Characteristic changes in tissue temperature and light-scattering signals were used to terminate laser irradiation. RESULTS: Effective reshaping was accomplished for both thin (1.5-mm) and thick (2.1-mm) specimens. Following reshaping, specimens were stored in saline solution at 4 degrees C for 21 days. No return to the original flat configuration was noted during this period. CONCLUSIONS: The prototype device effectively reshapes flat native porcine cartilage into curve configurations. The use of optical and thermal signals provides effective feedback control for optimizing the reshaping process.

Animals↗
PubMed2000

Assessment of fetal scalp oxygen saturation determination in the sheep by transmission pulse oximetry.

OBJECTIVE: Electronic fetal heart rate monitoring has an unacceptable false-positive nonreassuring rate, which results in an excess of operative interventions. As a more objective measure of fetal oxygenation, fetal scalp pulse oximetry has been used to assess fetal blood oxygen saturation (SO (2)). The current devices use reflectance oximetry, which has inherent limitations. These include varying depths of signal penetration, variation with position, and potential for optical interference. In this study we evaluated a newly developed transmission pulse oximetry device consisting of transmitter and receiver diodes mounted within the coil of a standard scalp electrode (Spiral O(2)CTG; Respironics Inc, Marietta, Ga). STUDY DESIGN: Six pregnant ewes at 127 to 135 days' gestation (term, 145 days' gestation) were anesthetized, intubated, and prepared with a femoral artery catheter. Fetuses were prepared with brachial artery and jugular vein catheters. Maternal inspired oxygen fraction was titrated from 21% to 3%. Oximetry O(2)CTG devices were positioned on the fetal scalp, and recordings were compared with directly determined fetal arterial pH, PO (2), and SO (2) values. RESULTS: Maternal SaO (2) and PaO (2) ranged from 102% to 16% and 110 to 18 mm Hg, respectively. Fetal SaO (2) and PaO (2) ranged from 76% to 12% and 28 to 8 mm Hg, respectively. There was excellent correlation between direct fetal SaO (2) and scalp SO (2) (r (2) = 0.90; scalp SO (2) = 0.79 SaO (2) + 6.89). With an SaO (2) of <30% as the cutoff point for assessment of fetal compromise, scalp SO (2) measurements had a 94% +/- 10% specificity and a 94% +/- 10% positive predictive value. CONCLUSION: (1) Preliminary studies of the Spiral O(2)CTG sensor demonstrated high correlation of scalp SO (2) with fetal SaO (2). (2) Although potential inaccuracies remain, transmission oximetry may offer potential advantages in consistency, ease of application, and technology with respect to the current reflection oximeter devices.

Animals↗
PubMedDate not supplied

An artificial compound eye for stereoendoscopy.

A scanning endoscope has been designed with the ability to both project three-dimensional images and provide precise measurements of internal structures. This is beneficial for minimally invasive surgery, where surgeons suffer from a lack of depth perception, limited field of view, and the absence of a reference frame for dimensional measurements. Borrowing from the insect compound eye, the design uses an array of prisms, each facing a different direction but with overlapping fields of view. The prisms redirect their respective images normal to a fibre optic imaging plane and are individually controlled by electro-chromic shutters. The device thereby retains the ability to scan in multiple directions without mechanical parts and uses only a single camera. Comparison of the overlapping images with known prism positions allows for the calculation of absolute coordinates. Results from large-scale models show that the technology is plausible, and fabrication methods for a smaller device are discussed.

Depth Perception↗
PubMed1998

Development of the optical waveguide solar lighting system for space-based plant growing.

This article summarizes the study on the Optical Waveguide (OW) Solar Lighting System for space-based plant growing. In the OW solar lighting system, solar radiation is collected by the concentrator, which transfers the concentrated solar radiation to the OW transmission line consisting of low-loss optical fibers. The OW line transmits the solar radiation to the plant growing units where the solar radiation from the optical fibers is defocused and directed to the plants for optimum intensity for plant growing. In this study, the laboratory OW solar lighting system was constructed and tested for plant growth. The OW system consists of: 1) tracking reflective concentrators; 2) the optical waveguide transmission line; and 3) the plant lighting device. Results of the performance tests and the plant growth tests of the OW solar lighting system showed that the OW system is a viable plant lighting system for growing plant in space.

Ecological Systems, Closed↗
PubMed2000

A streptavidin surface on planar glass substrates for the detection of biomolecular interaction.

Based on the requirements of biomolecular interaction analysis on direct optical transducers, a streptavidin surface is examined. A general protocol was developed allowing the immobilization of biotinylated compounds using the rife biotin-streptavidin system. This type of surface modification can be applied to all biosensors using glass surfaces as sensor devices. Reflectometric interference spectroscopy (RIfS), a label-free, direct optical method was used to demonstrate the quality of the transducer surfaces. The surface modification is based on an aminofunctionalized polyethylene glycol layer covalently bound to the silica surface of the transducer and shows very little nonspecific binding. Biotin molecules can be easily coupled on such layers. Streptavidin followed by a biotinylated estrone derivative was immobilized by incubation of the biotinylated transducer surface. For the streptavidin layer we obtained interference signals corresponding to a protein monolayer. Finally, using a surface prepared as described above, biomolecular interaction experiments with an antibody against estrone were carried out to show the quality of the transducer surface. With RIfS all of the affinity-based surface modifications can be detected online and time resolved.

Antibodies↗
PubMedDate not supplied

Contrast and glare sensitivity after implantation of AcrySof and Human Optics 1CU intraocular lenses.

PURPOSE: To evaluate contrast and glare sensitivity of a newly developed, potentially accommodative intraocular lens. METHODS: The clinical interventional prospective randomized study included 20 patients (23 eyes) undergoing standard phacoemulsification with clear cornea incision in topical anesthesia. In the study group (10 eyes), the 1CU Human Optics intraocular lens (optics diameter 5.5 mm) was implanted. The control group (13 eyes) received the monofocal AcrySof intraocular lens (optics diameter: 6.0 mm). Using a newly developed contrast measuring device, contrast and glare sensitivity were tested 4 weeks after surgery. RESULTS: The study group and control group did not vary significantly in contrast (p=0.38) or glare sensitivity (p=0.52). CONCLUSIONS: The results suggest that the newly developed 1CU Human Optics intraocular lens and the standard AcrySof intraocular lens do not vary significantly in glare and contrast sensitivity.

Acrylic Resins↗
PubMed2001

Characteristics of the pediatric/adolescent low-vision population at the Illinois School for the Visually Impaired.

BACKGROUND: There are few descriptive studies of children and adolescents with low vision in the United States. Our study describes a pediatric/adolescent population at the Illinois School for the Visually Impaired (ISVI), detailing the etiologies of low vision and the devices prescribed. METHODS: A retrospective record review was conducted of 260 consecutive students who had been examined at the twice-yearly Lions of Illinois Low Vision Clinic at ISVI between the years 1991 and 1999. Data collected included age, race, sex, best-corrected visual acuity, ocular diagnoses, the etiology of low vision (if known), and low-vision devices prescribed. RESULTS: The population was 60% male. Ages ranged from less than 1 year to 20 years of age. The mean best-corrected distance visual acuity was approximately 20/200. Optic atrophy, cataracts, and retinopathy of prematurity were significant etiologies of low vision; however, the largest group of patients had a diagnosis classified as "other." Hand-held telescopes, bifocals/high adds, and tinted lenses were the major low-vision devices prescribed. CONCLUSIONS: While optic atrophy, cataracts, and retinopathy of prematurity were common causes of vision impairment among students at ISVI, the largest group of students had an etiology from a wide range of disorders. Information on the causes of low vision can help with decisions on the allocation of research funds and resources for low-vision devices.

Adolescent↗
PubMed2006

Raman spectroscopic monitoring of droplet polymerization in a microfluidic device.

Microfluidic methodologies are becoming increasingly important for rapid formulation and screening of materials, and development of analytical tools for multiple sample screening is a critical step in achieving a combinatorial 'lab on a chip' approach. This work demonstrates the application of Raman spectroscopy for analysis of monomer composition and degree of conversion of methacrylate-based droplets in a microfluidic device. Droplet formation was conducted by flow focusing on the devices, and a gradient of component composition was created by varying the flow rates of the droplet-phase fluids into the microchannels. Raman data were collected using a fiber optic probe from a stationary array of the droplets/particles on the device, followed by partial least squares (PLS) calibration of the first derivative (1600 cm(-1) to 1550 cm(-1)) allowing successful measurement of monomer composition with a standard error of calibration (SEC) of +/-1.95% by volume. Following photopolymerization, the percentage of double bond conversion of the individual particles was calculated from the depletion of the normalized intensity of the C[double bond, length as m-dash]C stretching vibration at 1605 cm(-1). Raman data allowed accurate measurement of the decrease in double bond conversion as a function of increasing crosslinker concentration. The results from the research demonstrate that Raman spectroscopy is an effective, on-chip analytical tool for screening polymeric materials on the micrometre scale.

Journal Article↗
PubMed1987

Review of medical biosensors and associated materials problems.

Developers of biosensors as medical devices are using emerging technologies that incorporate chemical assays with fiber optics and semiconductors. These biosensors will eventually become indwelling catheters for monitoring blood analyte concentrations as well as functioning as controlled feedback elements for artificial organs. Materials used in these devices are subject to problems of manufacture and reliability as well as those induced by the human body's response to these "foreign agents." The Division of Mechanics and Materials Science in the Center for Devices and Radiological Health at the Food and Drug Administration has initiated a program to investigate factors that effect sensitivity, selectivity and reliability of sensors used in biological applications. Our group's principle focus is on sensors of chemical processes. This article is an outgrowth of our research efforts and is a review of some of the technologies that are currently available or becoming available for these applications. The goal of our research is to identify factors that will have an impact on the reliability of long-term implanted medical devices with particular attention to sensors used in feedback-controlled therapeutic systems.

Artificial Organs↗
PubMed2002

Fabrication of an optoelectrochemical microring array.

In this paper, we describe a novel approach for fabricating an optoelectrochemical microring array. The array was fabricated by coating individual optical fibers of 25-microm diameter with a 1-microm layer of gold nanoparticles via electroless gold deposition. A SAM layer around the individual gold-coated imaging fibers prevented electrical contact with neighboring ring electrodes. To achieve better mechanical stability and to make the device more practical, the electrode/fiber bundle comprising approximately 600 individual gold-coated optical fibers was dipped into epoxy. By polishing the ends of such a device, a ring microelectrode array comprising 600 individual and insulated ring electrodes was formed. To limit diffusional overlap of current, only 20-30% of the microring fiber/electrodes were wired. The inner diameter of the ring electrode is fixed by the diameter of the individual optical fibers (25 microm), while the outer radius is determined by the thickness of the deposited gold. The array was characterized using ferrocyanide in aqueous solution as a model electroactive species to demonstrate that this microelectrode array format exhibits steady-state currents at short response times. In addition, cyclic voltammetry experiments were performed using conventional potentiostats due to the amplification of current inherent in the array format. Finally, electrochemiluminescence at the ring electrode array was demonstrated through the oxidation of Ru(bpy)3(2+) in tri-n-propylamide in a pH 7 phosphate buffer solution, where the light generated was collected and detected via the fiber bundle.

Electrochemistry↗
PubMed1985

Adherence of coagulase-negative staphylococci to plastic tissue culture plates: a quantitative model for the adherence of staphylococci to medical devices.

The adherence of coagulase-negative staphylococci to smooth surfaces was assayed by measuring the optical densities of stained bacterial films adherent to the floors of plastic tissue culture plates. The optical densities correlated with the weight of the adherent bacterial film (r = 0.906; P less than 0.01). The measurements also agreed with visual assessments of bacterial adherence to culture tubes, microtiter plates, and tissue culture plates. Selected clinical strains were passed through a mouse model for foreign body infections and a rat model for catheter-induced endocarditis. The adherence measurements of animal passed strains remained the same as those of the laboratory-maintained parent strain. Spectrophotometric classification of coagulase-negative staphylococci into nonadherent and adherent categories according to these measurements had a sensitivity, specificity, and accuracy of 90.6, 80.8, and 88.4%, respectively. We examined a previously described collection of 127 strains of coagulase-negative staphylococci isolated from an outbreak of intravascular catheter-associated sepsis; strains associated with sepsis were more adherent than blood culture contaminants and cutaneous strains (P less than 0.001). We also examined a collection of 84 strains isolated from pediatric patients with cerebrospinal fluid (CSF) shunts; once again, pathogenic strains were more adherent than were CSF contaminants (P less than 0.01). Finally, we measured the adherence of seven endocarditis strains. As opposed to strains associated with intravascular catheters and CSF shunts, endocarditis strains were less adherent than were saprophytic strains of coagulase-negative staphylococci. The optical densities of bacterial films adherent to plastic tissue culture plates serve as a quantitative model for the study of the adherence of coagulase-negative staphylococci to medical devices, a process which may be important in the pathogenesis of foreign body infections.

Animals↗
PubMed1996

A prospective comparison of fibre-optic and fluid-filled single lumen bolt subdural pressure transducers in ventilated neurosurgical patients.

A clinical comparison was made between fibre-optic and fluid-filled Bolt subdural pressure transducers in ventilated head injured patients. Twelve subjects had both devices inserted in neighbouring sites. In two patients there were obvious technical problems with the fibre-optic system and the results were therefore excluded from further analysis. In the remaining 10 patients, 2167 pairs of simultaneous recordings were made for up to 9 days and the degree of correspondence studied. A quarter of paired readings differed by more than 5 mmHg. There was no evidence of any overall bias, but in individual patients one device often read higher or lower than the other. The proportion of closely corresponding readings tended to diminish after 4 days. Therapeutically relevant episodes, where treatment might have been initiated on the basis of the readings from only one of the two systems, were equally likely with both devices and occurred on average approximately every 30 h. The relative accuracy of the two devices remains uncertain, but there is evidence suggesting that both were prone to errors.

Adolescent↗
PubMed1997

[Experience in the use of flow scintillator Cobas Micros-18 OT in hematological practice].

Clinical analysis of the blood is a most prevalent investigation in practical medicine. The need in effective assessment of the results of blood analysis prompted the creation of automated flow systems. Our task was to analyze the blood of normal subjects and patients by Hoffmann La Roche Cobas Micros-18 OT (France). It is a completely automated hematological analyzer used for in vitro diagnostic tests of whole blood. The work consisted of two steps: 1) comparison of the results of leukocyte and red cell counting by Cobas Micros and Goryayev chamber and 2) assessment of the leukocyte formula in blood donors and patients with diseases other than hematological by the Cobas Micros device and compare the results with the data of visual assessment in optic microscope. The results of analysis by the automated scintillator, Goryayev's chamber, and optic microscopy were compatible. Cobas Micros is very convenient for analysis of liquid blood on an outpatient and inpatient basis and during overall screenings. The device facilitates the deciphering of the leukocytic formula and assessment of the status of formed elements of the blood in mass screenings and detection of abnormalities.

Erythrocyte Count↗
PubMed2003

Effects of dehydration on the optical properties of in vitro porcine liver.

BACKGROUND AND OBJECTIVES: It is of crucial importance to determine the effects of dehydration on the optical properties of tissue so that optimization of therapy and device for laser applications in medicine can be made. STUDY DESIGN/MATERIALS AND METHODS: After being incubated directly or indirectly in an oven of 37 degrees C for different periods of time, the porcine liver samples were weighed with an electronic scale and their optical properties were measured by a double integrating sphere system. RESULTS: When samples were incubated directly for 20 hours, the average weight loss was 68.5% +/- 1.2%, and the absorption coefficient and scattering coefficient increased 146.1% +/- 26.9% and 10.8% +/- 1.1%, respectively. In comparison, there was only 21.5% +/- 1.0% of water loss for the control samples, and the absorption coefficient increased 30.7% +/- 7.6%, while the reduced scattering coefficient increased 386.5% +/- 29.7%. The effective attenuation coefficients increased 111% and 103% for dehydration group and control group, respectively. CONCLUSIONS: The absorption coefficient and effective attenuation coefficient increase with dehydration level of tissue. However, there is no direct correlation between dehydration and reduced scattering coefficient.

Animals↗
PubMed2006

A standardized method to create optic nerve crush: Yasargil aneurysm clip.

It is often difficult to compare results obtained by different investigators on nerve compression injuries, owing to differences in method of pressure application and noncomparable pressure levels. In the present study, we described a new method to crush the optic nerve by using a specially designed and commercially available device. We think that standardization of the compression methods is necessary to compare interlaboratory results.

Animals↗
PubMed2004

Bacteria detection using disposable optical leaky waveguide sensors.

Novel disposable absorbing material clad leaky waveguide sensor devices (LWD) have been developed for the detection of pathogenic particles such as bacteria. These chips are tailored to give the maximum extension of the evanescent field at the sensor surface in order to place the entire volume of the bacteria captured by immobilized antibodies on the chip surface within this field. This in turn increases the interaction of the light with the bacteria's bulk volume. Disposable LWD chips were fabricated at room temperature and without the use of expensive fabrication equipment. These LWDs have been characterised by detecting refractive index (RI) changes, scattering and fluorescence from bacterial spores at the sensor surface when illuminated at the coupling angle. The detection limit of Bacillus subtilis var. niger (BG) bacterial spores was 10(4) spores/ml and the illumination intensity of the spores was found to be three times greater than the illumination intensity generated using the surface plasmon resonance (SPR).

Bacillus↗

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