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Choroidal imaging biomarkers
摘要： The choroid is the vascular coat of the eye,and its role has been studied in multiple chorioretinal disorders. The recent advancements in choroidal imaging techniques including enhanced depth imaging optical coherence tomography (EDI-OCT), swept source (SS-OCT), enface OCT and OCT angiography have facilitated an in-depth analysis of choroid. The gradual shift from manual to automated segmentation and binarization methods have led to precise and reproducible measurements of choroidal parameters. These qualitative and quantitative parameters, called choroidal imaging biomarkers, have evolved over the past decade from a simple linear subfoveal choroidal thickness to more complex 3 dimensional (3-D) choroidal reconstruction thus widening the spectrum encompassing multiple parameters. These biomarkers have provided a better understanding of the pathogenesis, are helpful in diagnostic dilemmas, and in future may also help to devise treatment options. The lack of normative data, absence of standardized parameters and limitations of the imaging techniques, however, have led to ambiguity and difficulty in the interpretation of these variables. We attempt to address these lacunae in the literature and provide a basic understanding of the choroid in both health and disease using these choroidal biomarkers.
关键词： Optical coherence tomography angiography (OCTA),En-face OCT,Swept source optical coherence tomography (SS-OCT),Choroidal thickness,Choroidal vascularity index (CVI),Choroidal imaging biomarkers,Choroidal volume
更新于2025-09-23 15:21:21
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Comparison of ultrasonic pachymetry and Fourier-domain optical coherence tomography for measurement of corneal thickness in dogs with and without corneal disease
摘要： Several ultrasonic and Fourier-domain optical coherence tomography (FD-OCT) pachymeters are used to measure corneal thickness in canine patients and research subjects. This study assessed the reliability of and consistency between two ultrasonic pachymetry (USP) devices, Pachette 3 and Accupach VI, as well as automated and manual measurements obtained using FD-OCT in dogs with and without corneal disease. Corneal thickness measurements were compiled from 108 dogs and analyzed using mixed effects linear regression, with Bonferonni adjustments for post-hoc comparisons, to determine the effects of age, weight and disease state. Data are presented as predicted mean ± standard error. Canine corneal disease can result in marked increases in thickness that frequently exceed the upper limits of measurement of some pachymetry devices developed for human use. In this study, the corneas of dogs with endothelial disease or injury frequently exceeded the upper limits of quantitation of 999 and 800 μm, respectively. Using values <800 μm for the Accupach VI and automated FD-OCT pachymeters, respectively. Of the two devices where measurements >1000 μm were obtained, manual FD-OCT demonstrated less variability than the Pachette 3. Corneal thickness increased linearly with age and weight with an increase of 6.9 ± 0.8 μm/year and 1.6 ± 0.38 μm/kg body weight (P < 0.005 and P = 0.038, respectively).
关键词： Corneal thickness,Corneal endothelial dystrophy,Optical coherence tomography,Ultrasonic pachymetry,Canine
更新于2025-09-23 15:21:21
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Point-of-care endoscopic optical coherence tomography detects changes in mucosal thickness in ARDS due to smoke inhalation and burns
摘要： Background: The prevalence of acute respiratory distress syndrome (ARDS) in mechanically ventilated burn patients is 33%, with mortality varying from 11–46% depending on ARDS severity. Despite the new Berlin definition for ARDS, prompt bedside diagnosis is lacking. We developed and tested a bedside technique of fiberoptic-bronchoscopy-based optical coherence tomography (OCT) measurement of airway mucosal thickness (MT) for diagnosis of ARDS following smoke inhalation injury (SII) and burns. Methods: 16 female Yorkshire pigs received SII and 40% thermal burns. OCT MT and PaO2-to-FiO2 ratio (PFR) measurements were taken at baseline, after injury, and at 24, 48, and 72h after injury. Results: Injury led to thickening of MT which was sustained in animals that developed ARDS. Significant correlations were found between MT, PFR, peak inspiratory pressure (PIP), and total infused fluid volume. Conclusions: OCT is a useful tool to quantify MT changes in the airway following SII and burns. OCT may be effective as a diagnostic tool in the early stages of SII-induced ARDS and should be tested in humans.
关键词： Burns,Bronchoscopy,Optical coherence tomography,Smoke inhalation injury,Acute respiratory distress syndrome
更新于2025-09-23 15:21:21
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Usefulness of peripapillary nerve fiber layer thickness assessed by optical coherence tomography as a biomarker for Alzheimer’s disease
摘要： The use of optical coherence tomography (OCT) has been suggested as a potential biomarker for Alzheimer’s Disease based on previously reported thinning of the retinal nerve fiber layer (RNFL) in Alzheimer’s disease’s (AD) and Mild Cognitive Impairment (MCI). However, other studies have not shown such results. 930 individuals (414 cognitively healthy individuals, 192 probable amnestic MCI and 324 probable AD) attending a memory clinic were consecutively included and underwent spectral domain OCT (Maestro, Topcon) examinations to assess differences in peripapillary RNFL thickness, using a design of high ecological validity. Adjustment by age, education, sex and OCT image quality was performed. We found a non-significant decrease in mean RNFL thickness as follows: control group: 100,20 ± 14,60 μm, MCI group: 98,54 ± 14,43 μm and AD group: 96,61 ± 15,27 μm. The multivariate adjusted analysis revealed no significant differences in mean overall (p = 0.352), temporal (p = 0,119), nasal (p = 0,151), superior (p = 0,435) or inferior (p = 0,825) quadrants between AD, MCI and control groups. These results do not support the usefulness of peripapillary RNFL analysis as a marker of cognitive impairment or in discriminating between cognitive groups. The analysis of other OCT measurements in other retinal areas and layers as biomarkers for AD should be tested further.
关键词： retinal nerve fiber layer,optical coherence tomography,Alzheimer’s Disease,cognitive impairment,biomarker
更新于2025-09-23 15:21:21
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Optical Coherence Tomography as an Oral Cancer Screening Adjunct in a Low Resource Settings
摘要： Oral cancer is the sixth most common cancer worldwide, predominantly seen in low and middle-income countries (LMIC). Two thirds of all cases are detected at a late stage when prognosis and treatment outcomes are poor. Oral lesions are commonly detected by visual inspection, followed by invasive surgical biopsy and time-consuming histopathological analysis. Optical coherence tomography (OCT), a minimally invasive tomographic imaging technology, can be used to non-invasively identify premalignant or malignant change in the oral mucosa. In this study, a mobile OCT imaging system was designed, constructed, and tested for its performance as a point-of-care oral diagnostic device in an LMIC. 20 patients with suspicious oral lesions and 10 healthy subjects were enrolled in this pilot study. Two-dimensional (2-D) OCT images as well as clinical examination data, risk habit history, and histopathology were collected. OCT images for healthy oral mucosa, dysplasia, and malignancy were evaluated in a blinded fashion by visual scoring and computed image processing techniques. It was found that the OCT image processing algorithm performed at or exceeded the performance of visual observer scoring of OCT images.
关键词： cancer,Image classification,optical coherence tomography,biomedical optical imaging,biomedical image processing
更新于2025-09-23 15:21:21
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The Additional Diagnostic Value of Optical Coherence Tomography (OCT) and Its Application Procedure in A Wide Variety of Avian Species
摘要： Objective: The current study introduced OCT as a novel tool in clinical veterinary ophthalmology in a much wider variety of free-living avian species than hitherto studied. Methods: OCT was tested and performed in 39 free-living birds (21 species of 12 families) and compared to direct ophthalmoscopy. Birds were examined with combinations of different restraints (manual restraint or fixation on a holding device) and different anaesthesia regimes (none, sedation, general anaesthesia). Inter- and intra-species specific variations of the general procedure, the restraint methods and the clinical findings were evaluated. Results: OCT was possible in all examined avian species (from 40 g up to 7720 g) and superseded direct ophthalmoscopy in quality and quantity of ophthalmological findings. All restraint methods enabled OCT examination, however combination of general anaesthesia and a holding device provided the most rapid and subjectively the least stressful examination technique. Stability, stress reduction, head angle and distance from the OCT device were important factors influencing volume scanning quality. Sixteen, out of 39 birds, presented ocular abnormalities detected by OCT (compared to only five birds when using direct ophthalmoscopy). OCT with included fundus images offered an objective assessment of retinal changes. Retinal abnormalities included changes of fundus pigmentation, drusenoid changes and severe retinal and choroidal degenerations. Species-specific variations of retinal layer dimensions and of foveal structures were evident. Conclusion: OCT is a promising, non-invasive method, which significantly compliments standard techniques. OCT is applicable to a wide variety of avian species; it provides high quality cross-sectional images of the retina, enabling accurate and improved diagnosis and prognosis of therapies. An assessment of the visual capabilities of traumatised birds is a major factor for their rehabilitation and survival in the wild. Finally, this method is an excellent tool in interdisciplinary retinal research, providing novel insights into the diversity of very specialized structural adaptations of avian retina.
关键词： Direct ophthalmoscopy,Raptor,Retina,Optical coherence tomography,Avian ophthalmology
更新于2025-09-23 15:21:21
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New clinical ultrahigh-resolution SD-OCT using A-scan matching algorithm
摘要： Purpose A new clinical ultrahigh-resolution spectral domain optical coherence tomography (UHR-SD-OCT) system using an original averaging technique named BA-scan matching algorithm^ was developed. The aim of this study was to determine whether our new UHR-SD-OCT system can obtain clearer sectional images of the retina than conventional standard resolution SD-OCT systems (SR-SD-OCT). Methods We recorded horizontal B-scan images of 42 normal eyes using our new UHR-SD-OCT device (Bi-μ, Kowa) and a conventional SR-SD-OCT (Spectralis, Heidelberg). To evaluate the clarity of the interdigitation zone (IZ) subjectively, the integrity of IZ was divided into three types by two raters. To evaluate the clarity of the IZ objectively, a peak height score (PHS) was calculated at five different points of the macula using the longitudinal reflectivity profile. Results The mean (± SD) of the subjective visibility score of the IZ in the UHR-SD-OCT images was 2.64 ± 0.54 which was significantly higher than the 2.46 ± 0.46 in the SR-SD-OCT images (P = 0.02). The PHS was also significantly higher for the UHR-SD-OCT than for the SR-SD-OCT images at all five locations (all P < 0.01). Conclusion The results indicate that the newly developed clinical UHR-SD-OCT instrument using the A-scan matching algorithm can obtain clearer images of the IZ, and they suggest that this device should be clinically useful in detecting finer structural abnormalities of the outer retina.
关键词： Spectral domain,Ultrahigh-resolution,Optical coherence tomography (OCT),Interdigitation zone,Retina
更新于2025-09-23 15:21:21
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[Springer Tracts in Modern Physics] Parity-time Symmetry and Its Applications Volume 280 || Parity-Time-Symmetric Optical Lattices in Atomic Configurations
摘要： In this chapter, we show how to theoretically design and experimentally construct exact parity-time (PT) symmetric optical lattices with gain and loss in atomic configurations. By making use of the advantages of light-induced atomic coherence in multi-level atomic systems, spatially extended gain and loss arrays with real-time reconfigurability and multiple-parameter tunability can be effectively obtained in hot atomic vapors. We have constructed periodically alternative gain-loss structures with two very different schemes based on spatially-arranged optical induction techniques. With the required symmetric/antisymmetric spatial distributions for the real/imaginary parts of the refraction index satisfied, PT-symmetric optical lattices can be achieved with easy controllability. The dynamic behaviors of light propagating inside the induced non-Hermitian optical lattices are investigated by measuring the relative phase difference between two adjacent gain and loss channels.
关键词： Light-Induced Atomic Coherence,Non-Hermitian Optical Lattices,Atomic Configurations,Parity-Time-Symmetric Optical Lattices,Gain and Loss
更新于2025-09-23 15:21:21
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Outer Retinal Changes Including the Ellipsoid Zone Band in Usher Syndrome 1B due to <i>MYO7A</i> Mutations
摘要： PURPOSE. To study transition zones from normal to abnormal retina in Usher syndrome IB (USH1B) caused by myosin 7A (MYO7A) mutations. METHODS. Optical coherence tomography (OCT) scattering layers in outer retina were segmented in patients (n ? 16, ages 2–42; eight patients had serial data, average interval 4.5 years) to quantify outer nuclear layer (ONL) and outer segments (OS) as well as the locus of EZ (ellipsoid zone) edge and its extent from the fovea. Static perimetry was measured under dark-adapted (DA) and light-adapted (LA) conditions. RESULTS. Ellipsoid zone edge in USH1B-MYO7A could be located up to 238 from the fovea. Ellipsoid zone extent constricted at a rate of 0.518/year with slower rates at smaller eccentricities. A well-de?ned EZ line could be associated with normal or abnormal ONL and/or OS thickness; detectable ONL extended well beyond EZ edge. At the EZ edge, the local slope of LA sensitivity loss was 2.6 (61.7) dB/deg for central transition zones. At greater eccentricities, the local slope of cone sensitivity loss was shallower (1.1 6 0.4 dB/deg for LA) than that of rod sensitivity loss (2.8 6 1.2 dB/deg for DA). CONCLUSIONS. In USH1B-MYO7A, constriction rate of EZ extent depends on the initial eccentricity of the transition. Ellipsoid zone edges in the macula correspond to large local changes in cone vision, but extramacular EZ edges show more pronounced losses on rod-based vision tests. It is advisable to use not only the EZ line but also other structural and functional parameters for estimating natural history of disease and possible therapeutic effects in future clinical trials of USH1B-MYO7A.
关键词： myosin 7A,retinitis pigmentosa,optical coherence tomography,photoreceptors
更新于2025-09-23 15:21:21
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Long Exciton Dephasing Time and Coherent Phonon Coupling in CsPbBr <sub/>2</sub> Cl Perovskite Nanocrystals
摘要： Fully-inorganic cesium lead halide perovskite nanocrystals (NCs) have shown to exhibit outstanding optical properties such as wide spectral tunability, high quantum yield, high oscillator strength as well as blinking-free single photon emission and low spectral diffusion. Here, we report measurements of the coherent and incoherent exciton dynamics on the 100 fs to 10 ns timescale, determining dephasing and density decay rates in these NCs. The experiments are performed on CsPbBr2Cl NCs using transient resonant three-pulse four-wave mixing (FWM) in heterodyne detection at temperatures ranging from 5 K to 50 K. We found a low-temperature exciton dephasing time of 24.5±1.0 ps, inferred from the decay of the photon-echo amplitude at 5 K, corresponding to a homogeneous linewidth (FWHM) of 54±5 μeV. Furthermore, oscillations in the photon-echo signal on a picosecond timescale are observed and attributed to coherent coupling of the exciton to a quantized phonon mode with 3.45 meV energy.
关键词： quantum dots,coherence,four wave mixing,nanocrystals,heterodyne detection,Perovskite,T2,lead halide,photon echo,phonons
更新于2025-09-23 15:21:21