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The effect of the optical design of multifocal contact lenses on choroidal thickness
摘要： Studies have found reduced myopia progression with multifocal contact lenses, albeit with an unclear mechanism behind their protective effect. It is hypothesized that the induced myopic defocus of the addition zones of the multifocal contact lenses leads to choroidal thickening and therefore inhibits eye growth. In the current study, the effect of the optical design of multifocal contact lenses on choroidal thickness was investigated. Eighteen myopic participants wore four different contact lenses ((1) single-vision lenses corrected for distance, (2) single-vision lenses with +2.50 D full-field defocus, (3) Multifocal center-distance design, (4) Multifocal center-near design, both with addition power +2.50 D) for 30 min each on their right eye. Automated analysis of the macular choroidal thickness and vitreous chamber depth were performed before and after the wear of each of the contact lenses. Peripheral refraction profiles in primary gaze were obtained using eccentric photorefraction prior to contact lens wear. Choroidal thickness and vitreous chamber depth showed no significant differences to baseline with any of the contact lenses (all p > 0.05). Choroidal thickness increased by +2.1 ± 11.1 μm with the Multifocal center-distance design, by +2.0 ± 11.1 μm with the full-field defocus lens, followed by the Multifocal center-near design with +1.6 ± 11.3 μm and the single-vision contact lens correcting for distance with +0.9 ± 11.2 μm. Multifocal contact lenses have no significant influence on choroidal thickness after short-term wear. Therefore, changes in choroidal thickness might not be the main contributor to the protective effect of multifocal contact lenses in myopia control.
关键词： multifocal contact lenses,choroidal thickness,optical design,defocus,myopia control
更新于2025-09-10 09:29:36
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Clinical Correlation between Retinal Sensitivity and Foveal Thickness in Retinitis Pigmentosa Patients
摘要： Purpose: To investigate the relationship between retinal structure and retinal sensitivity comparing data obtained using spectral-domain optical coherence tomography (SD-OCT) and microperimetry in retinitis pigmentosa (RP) and healthy patients. Methods: A total of 49 patients (98 eyes) with RP were divided into 4 groups according to the OCT findings: group A, patients with no macular changes; group B, patients with cystoid macular edema (CME); group C, patients with vitreomacular traction (VMT); group D, patients with retinal thinning. As a control group, we enrolled 27 healthy subjects. All subjects underwent a complete ophthalmologic examination, including SD-OCT and microperimetry. For the statistical analysis, Pearson correlation test and linear regression analysis were used. A p value <0.05 was considered statistically significant. Results: We did not find any significant difference in best-corrected visual acuity (BCVA), foveal thickness, or retinal sensitivity between group A and the healthy subjects (p>0.05). In group B, linear regression of logMAR versus foveal thickness and retinal sensitivity versus foveal thickness gave r values of 0.931 and 0.786, respectively. In group C, r values were 0.786 and 0.842, respectively, while in group D they were 0.816 and 0.795. Conclusions: This article shows the first application of the new microperimeter MP3 in patients with RP, which has proven to be very sensitive in detecting functional abnormalities in all the patients. Future studies should investigate the relationships among photoreceptor cell loss, retinal sensitivity, and fixation in patients with RP.
关键词： MP3,Microperimetry,Retinitis pigmentosa,Optical coherence tomography,Retinal sensitivity,Foveal thickness
更新于2025-09-10 09:29:36
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - All-Electronic High-Resolution Terahertz Thickness Measurements
摘要： Broadband laser based terahertz systems become currently established for inline multilayer paint inspection in the automotive industry. This technology has also proven to be suitable for inspections of certain multilayer plastic structures with up to a few millimeters of thickness. We present a complementary technique for the measurement of dielectric multilayer structures with thicknesses of submillimeter to several centimeters, using frequency-modulated continuous-wave electronic transceivers. In order to resolve layers below the inherent resolution limit by the modulation bandwidth, we take advantage of model-based signal processing techniques.
关键词： signal processing,thickness measurements,frequency-modulated continuous-wave,terahertz,multilayer structures
更新于2025-09-10 09:29:36
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Numerical Simulation and Optimization of An a-ITZO TFT Based on a Bi-Layer Gate Dielectrics
摘要： This work is an optimization study by numerical simulation of the performance of a bottom gate amorphous indium tin zinc oxide thin film transistor (a-ITZO TFT) using SILVACO-ATLAS software. The optimization process is focused on the gate dielectric conception, namely, thicknesses, number of layers and materials. The electrical characteristics calculated are the gate capacitance per unit area (Ci), the on-current (Ion), the on–off current (Ion=Ioff ) ratio, the threshold voltage (VT), the field-effect mobility (lFE), the sub-threshold swing (SS) and the resistivity (q) of the a-ITZO channel. The obtained results indicate that using a bi-layer dielectrics (SiO2/HfO2) with a relatively high thickness (BDT ? 70 nm) improves the electrical response compared to TFT based on the mono-layer dielectric, for the same physical thickness, and the optimized outputs obtained are Ci ? 3:45 (cid:2) 10(cid:3)7 F/cm2, Ion ? 4:12 (cid:2) 10(cid:3)5 A, lFE ? 29:34 cm2 V(cid:3)1 s(cid:3)1, Ion=Ioff ? 4:67 (cid:2) 108, VT ? (cid:3) 0:45 V, SS ? 6:42 (cid:2) 10(cid:3)2 V/dec, and q ? 2:60 (cid:2) 10(cid:3)2 X cm.
关键词： Silvaco Atlas,equivalent oxide thickness,SiO2,a-ITZO,HfO2,TFT,high-k
更新于2025-09-10 09:29:36
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Enhanced Depth Imaging Optical Coherence Tomography in Adult-Onset Foveomacular Vitelliform Dystrophy
摘要： Purpose: To compare mean choroidal thickness in patients with adult-onset foveomacular vitelliform dystrophy (AOFVD) and healthy subjects, to analyze patients with AOFVD in order to evaluate choroidal thickness disease-related changes, also in relation to the different stages of AOFVD disease and to the retinal pigment epithelium (RPE) features, and to correlate mean choroidal thickness with age in both groups. Methods: In this prospective observational cross-sectional study, a total of 63 eyes of 51 consecutive subjects were examined, consisting of a control group (n = 28 eyes) and the AOFVD group (n = 35 eyes). A complete ophthalmologic examination, fundus autofluorescence, and spectral-domain optical coherence tomography were performed in all patients. Results: Mean subfoveal choroidal thickness was 214.78 ± 62.35 μm in healthy subjects and 222.31 ± 73.29 μm in the AOFVD group (p = 0.33). In the vitelliruptive group, the mean choroidal thickness was significantly thicker than in the control group at each choroidal location. Mean choroidal thickness was significantly increased in the pseudohypopyon stage when compared to the vitelliform one (+66.34 μm, p = 0.02). Eyes with subretinal fluid (SRF) showed significantly thicker choroid when compared with those without SRF. No significant correlations were found between age and choroidal thickness in the study group. Conclusions: The study of the choroid in patients with AOFVD suggested a possible role in the pathologic changes during the different stages of disease, and could help us to evaluate progression of the disease. Greater choroidal thickness associated with SRF and RPE bumps are signs of RPE alterations and could be related to evolution of the AOFVD lesion to a different stage.
关键词： Choroidal thickness,Enhanced depth imaging optical coherence tomography,Adult-onset foveomacular vitelliform dystrophy
更新于2025-09-10 09:29:36
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Visualization of the pulp chamber roof and residual dentin thickness by spectral-domain optical coherence tomography in vitro
摘要： The aim of this study was to evaluate the ability of spectral-domain optical coherence tomography (SD-OCT) to display the roof of the pulp chamber and to estimate the residual dentin thickness (RDT) of the pulp complex. The roots of 20 extracted human molars were embedded in epoxy resin, and crowns were longitudinally sectioned in the mesial-distal direction, exposing the pulp chamber. The coronal part of the crown was removed up to an RDT to the pulp chamber roof of 2 mm. Samples were imaged by SD-OCT from coronal view and by light microscopy (LM) in the sagittal plane. Using a microtome, dentin was subsequently removed in four levels from the occlusal aspect in steps of 250 μm. At each level, RDT was documented and measured by both methods. The data were compared (Spearman’s rho correlation coefficient, Wilcoxon signed-rank test). Using OCT, the roof of the pulp chamber was first displayed at a maximum RDT of 1.94 mm. The minimal RDT that could be imaged by OCT was 0.06 mm. Values from both methods were strongly correlated (r, 0.83–0.95; pi ≤ 0.05) and differed significantly for large RDTs (dentin levels 1, 2; pi < 0.05) but not for small RDTs (levels 3, 4; pi ≥ 0.226). The roof of the dental pulp chamber could be already visualized by SD-OCT with a RDT of 1.94 mm. Therefore, the method could be a useful diagnostic tool during the preparation of deep dentin cavities and might help to preserve the integrity of the pulp chamber.
关键词： Pulp protection,Residual dentin thickness,OCT,Dental pulp,Deep dentin cavities,Diagnosis
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Near-Real Time Detection of the Re-Opening of the Weddell Polynya, Antarctica, from Spaceborne Infrared Imagery
摘要： A hole in the Antarctic sea ice cover, the Weddell Polynya, unexpectedly re-opened in winter 2017 for the first time since 1976. Models suggest that the polynya opened because warm oceanic water moved up to the surface, melting the ice from below. Here three temperature thresholds applied to near-hourly spaceborne infrared imagery (AVHRR) successfully detect the appearance of a warm spot up to five days before the polynya opened in June and September 2017. Traditional sea ice concentration and thickness criteria could only detect the polynya once it was open. An automatised warning system, using near-real time passive monitoring of warm spots, would allow researchers to reroute vessels or autonomous sensors in order to finally study the polynya as a whole when it opens again, from its preconditioning to its impacts on the climate system.
关键词： AVHRR,infrared imagery,Weddell Polynya,sea ice concentration,sea ice thickness,Antarctic sea ice
更新于2025-09-10 09:29:36
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[IEEE 2018 International CET Conference on Control, Communication, and Computing (IC4) - Thiruvananthapuram, India (2018.7.5-2018.7.7)] 2018 International CET Conference on Control, Communication, and Computing (IC4) - Computerized Detection of Macular Edema Using OCT Images Based on Fractal Texture Analysis
摘要： Macular edema (ME) is a significant cause that results in blindness among majority. It happens due to the anomalous leakage and builds up of fluids within macular region. Anything that relates with the performance of eyes can drive the chances to become a ME patient. ME can occur as a downstream of eye related surgeries, degradation due to aging or any eye disorders causing inflammation. The main fact about ME that if the disease is not identified and diagnosed at the earlier stages, the chance of recovery is minimal and can ultimately affect the ability to see. One of the main causes of ME is the disease which can injure in the retina. Laser photocoagulation and blood vessels vitrectomy are the common method available now for diagnosing the disease. Optical Coherence Tomography alias OCT, an advanced imaging technique to capture retinal layer region. Different algorithms were implemented to detect ME from OCT images, but early detection of ME is not possible. This paper utilizes segmentation based fractal texture analysis (SFTA) to derive the feature vector. Graph based segmentation employs in the detection of layers and QDA classifies the ME images. This algorithm will help the ophthalmologist to treat the patient at early stages. The algorithm is deployed successfully on a macular edema dataset, with 97.5% accuracy rate.
关键词： layer detection,Graph shortest path,SFTA,thickness profile,OCT,Macular Edema,QDA
更新于2025-09-10 09:29:36
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Computable translucency as a function of thickness in a multi-layered zirconia
摘要： Statement of problem. Determining the relationship between variable thicknesses and the translucency of dental ceramics is essential for optimizing esthetics in different clinical situations. Purpose. The purpose of this in vitro study was to analyze the relationship between layer thickness and translucency of 2 multi-layered monolithic zirconia materials and to develop an equation by which the grade of translucency can be calculated dependent on the materials’ layer thicknesses in advance. Material and methods. Two semisintered multi-layered zirconia blanks, namely KATANA Zirconia Super Translucent Multi-Layered Disk (Noritake Dental Supply Co, Ltd) and Zirconia Ultra Translucent Multi-Layered Disk (UTML) (Noritake Dental Supply Co, Ltd), were sectioned (N=96) to separate the 4 layers (n=12 per layer): enamel layer, transition layer 1, transition layer 2, body layer. All specimens were sintered in a furnace (M2 Plus; Thermo-Star) at 1500°C for 2 hours and automatically polished under water cooling up to P2400 for the thicknesses of 1.6, 1.3, 1.0, 0.7, and 0.4 mm. Transmittance of visible light was measured using a spectrophotometer (Lambda 35; Perkin Elmer). Data were analyzed using the Kolmogorov-Smirnov, 2-way ANOVA, and Scheffé post hoc tests (a=.01) and curve fitting. Results. Analyzing the fitting of the values of the 8 material groups to the linear, exponential, and logarithmic curves, 7 of the 8 groups (not UTML body layer) fitted the most (R-square value closer to 1.0) to the logarithmic curve. Constants were obtained from the distance to the x-axis and the curvature. Conclusions. The methodology of this study provided the materials’ specific constants a and b by analyzing the translucency behavior of KATANA Super Translucent Multi-Layered Disk and Ultra Translucent Multi-Layered Disk in different thicknesses, allowing further translucency calculation by applying the developed formula and the constants.
关键词： zirconia,translucency,thickness,esthetics,dental ceramics
更新于2025-09-10 09:29:36
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High-speed Fizeau interferometry for film topography measurement during spray film interaction
摘要： This work presents a novel high-speed interferometric thickness measurement system for thin films (1 μm-23 μm). The system is based on a Fizeau-interferometer and combines a high-speed camera for 2-D topographic fringe images with a spectrally resolved white light interferometer. The aim of this combination is to overcome the ambiguities of the phase demodulation process during fringe pattern analysis. The system is able to measure spatially and temporally resolved film thickness distributions during fast processes. The measurement error of the system is around 5% compared to a commercial 0-D interferometer. First, the results during a diesel spray impingement onto a predefined diesel film are shown, and at the impingement point, an increase in a fluid volume of 24.3% can be seen.
关键词： interferometric thickness measurement,High-speed Fizeau interferometry,thin films,spray film interaction,film topography measurement
更新于2025-09-10 09:29:36