293 research outputs found
Retinex-qDPC: automatic background rectified quantitative differential phase contrast imaging
The quality of quantitative differential phase contrast reconstruction (qDPC)
can be severely degenerated by the mismatch of the background of two oblique
illuminated images, yielding problematic phase recovery results. These
background mismatches may result from illumination patterns, inhomogeneous
media distribution, or other defocusing layers. In previous reports, the
background is manually calibrated which is time-consuming, and unstable, since
new calibrations are needed if any modification to the optical system was made.
It is also impossible to calibrate the background from the defocusing layers,
or for high dynamic observation as the background changes over time. To tackle
the mismatch of background and increases the experimental robustness, we
propose the Retinex-qDPC in which we use the images edge features as data
fidelity term yielding L2-Retinex-qDPC and L1-Retinex-qDPC for high
background-robustness qDPC reconstruction. The split Bregman method is used to
solve the L1-Retinex DPC. We compare both Retinex-qDPC models against
state-of-the-art DPC reconstruction algorithms including total-variation
regularized qDPC, and isotropic-qDPC using both simulated and experimental
data. Results show that the Retinex qDPC can significantly improve the phase
recovery quality by suppressing the impact of mismatch background. Within, the
L1-Retinex-qDPC is better than L2-Retinex and other state-of-the-art DPC
algorithms. In general, the Retinex-qDPC increases the experimental robustness
against background illumination without any modification of the optical system,
which will benefit all qDPC applications
Confocal Blue Reflectance Imaging in Type 2 Idiopathic Macular Telangiectasia
PURPOSE. To report the characteristics of confocal blue reflectance imaging in type 2 idiopathic macular telangiectasia (type 2 IMT). METHODS. In a prospective observational cross-sectional study, both eyes of 33 patients with type 2 IMT were examined by means of fundus biomicroscopy, fundus photography, fluorescein angiography, and optical coherence tomography (OCT). Confocal blue reflectance (CBR) imaging was performed using a confocal scanning laser ophthalmoscope (HRA2; Heidelberg Engineering, Heidelberg, Germany). To compare the results derived from different imaging modalities, an analysis was performed using image analysis software (Heidelberg Eye Explorer; Heidelberg Engineering). RESULTS. CBR imaging revealed a parafoveal area of increased reflectance that was slightly larger than the area of hyperfluorescence in late-phase fluorescein angiography. The area usually encompassed an oval parafoveal area, but sectors could be spared. A parafoveal area of increased CBR was detected in 98% of eyes that showed angiographic evidence for type 2 IMT. CONCLUSIONS. CBR imaging is a new, noninvasive, and sensitive method that may contribute to differentiate type 2 IMT from other diseases. Abnormalities of macular pigment distribution and Miiller cell pathology may contribute to the phenomenon of increased CBR and thus the pathophysiology of type 2 IMT
Pupil-driven quantitative differential phase contrast imaging
In this research, we reveal the inborn but hitherto ignored properties of
quantitative differential phase contrast (qDPC) imaging: the phase transfer
function being an edge detection filter. Inspired by this, we highlighted the
duality of qDPC between optics and pattern recognition, and propose a simple
and effective qDPC reconstruction algorithm, termed Pupil-Driven qDPC
(pd-qDPC), to facilitate the phase reconstruction quality for the family of
qDPC-based phase reconstruction algorithms. We formed a new cost function in
which modified L0-norm was used to represent the pupil-driven edge sparsity,
and the qDPC convolution operator is duplicated in the data fidelity term to
achieve automatic background removal. Further, we developed the iterative
reweighted soft-threshold algorithms based on split Bregman method to solve
this modified L0-norm problem. We tested pd-qDPC on both simulated and
experimental data and compare against state-of-the-art (SOTA) methods including
L2-norm, total variation regularization (TV-qDPC), isotropic-qDPC, and Retinex
qDPC algorithms. Results show that our proposed model is superior in terms of
phase reconstruction quality and implementation efficiency, in which it
significantly increases the experimental robustness while maintaining the data
fidelity. In general, the pd-qDPC enables the high-quality qDPC reconstruction
without any modification of the optical system. It simplifies the system
complexity and benefits the qDPC community and beyond including but not limited
to cell segmentation and PTF learning based on the edge filtering property
Effect of combined water drinking test and dark room provocative testing in Caucasian eyes with narrow angles
Purpose: To assess the usefulness of water drinking test and dark room provocative testing (WDT + DRPT) in current clinical practice by evaluating input parameters from Swept-source Optical Coherence Tomography (SS-OCT) images, and to determine if clinical factors like axial length, central endothelial cell count (CECC) and retinal nerve fibre layer thickness (RNFL) thickness are associated with a positive WDT + DRPT. Methods: SS-OCT examination was performed in consecutive subjects presenting as new patients in the outpatient clinic aged > 40 years. If at least one eye met the inclusion criteria (anterior chamber angles <20° and anterior chamber depth < 2.5 mm on SS-OCT), subjects were included in this study and WDT + DRPT was carried out. The eye with the smallest angle was analysed. The difference in parameters between eyes with a positive (≥8 mmHg) and negative (<8 mmHg) increase in intraocular pressure (IOP) after WDT + DRPT were statistically analysed. Second, the correlation between IOP increase after WDT + DRPT and anterior chamber angle parameters (RNFL thickness, CECC and axial length) was studied. Results: A total of 95 subjects with a mean age of 64 years were included. There was an association between IOP increase after WDT + DRPT and anterior chamber angle characteristics, however this was not of clinical significance. No positive results after WDT + DRPT were found in patients with anterior chamber angles ≥ 20°. Conclusions: The present findings indicate that this combined provocative test has no definite correlative or predictive value in angle closure disease. Further, the test is not useful in predicting early diagnosis or possible CECC or RNFL loss
The effect of oscillating Fermi energy on the line shape of the Shubnikov-de Haas oscillation in a two dimensional electron gas
The line shape of the Shubnikov-de Haas (SdH) oscillation has been analyzed
in detail for a GaAs/AlGaAs two-dimensional electron gas. The line shape, or
equivalently the behavior of the Fourier components, of the experimentally
observed SdH oscillation is well reproduced by the sinusoidal density of states
at the Fermi energy that oscillates with a magnetic field in a saw-tooth shape
to keep the electron density constant. This suggests that the broadening of
each Landau level by disorder is better described by a Gaussian than by a
Lorentzian.Comment: 7 pages,6 figures, minor revision
Lipoprotein Changes Following Consumption of Lutein-enriched Eggs are Associated with Enhanced Lutein Bioavailability
Abstract Lutein is concentrated in the retina and since it cannot be synthesized by the human body, its uptake depends on nutritional intake. Lutein-enriched eggs are a good lutein source, but whether changes in lipoprotein status following lutein-enriched egg consumption may affect an individual's lutein response is not yet clear. Data from three intervention trials with lutein-enriched eggs or products made from the enriched egg yolks were combined (n=294) and analyzed to investigate the dynamics of the lutein response in relation to lipoprotein levels. Cross sectional correlation was tested at baseline between lutein and lipoprotein profiles in all participants. Subsequently two groups were selected from the combined database whereby individuals receiving lutein-enriched egg yolks (n=137) were compared with controls not receiving eggs (n=117). Significant correlations between blood lutein concentrations and total cholesterol (r=0.309; p<0.001), HDL-C (r=0.246; p<0.001), LDL-C (r=0.241; p<0.001), ApoA1 (r=0.301; p<0.001), and ApoB100 (r=0.199; p<0.005) concentrations, but not with serum triglycerides were found at baseline. Following a three to twelve month intervention, blood lutein concentrations increased from 238 to 463 ng/ml (p<0.001) in the lutein group, whereas levels in controls remained unchanged. The lutein increase in the lutein-enriched egg group correlated significantly with changes in total cholesterol, HDL-C, LDL-C, ApoA1 and ApoB100 concentrations. To conclude, individuals showing the largest lipoprotein increase following egg consumption were also those with the strongest increase in blood lutein concentration. This indicates that therapies directed at altering lipoprotein levels may indirectly affect lutein bioavailability
Response:Early Phacoemulsification After Acute Angle Closure in Patients With Coexisting Cataract
In Reply:Early Phacoemulsification After Acute Angle Closure in Patients With Coexisting Cataract
Cost analysis of mydriasis strategies in cataract surgery care in the Netherlands
PURPOSE: To investigate the economic impact of an intracameral mydriatics and anesthesic agent (ICMA), topical mydriatics, and a mydriatic ocular insert in cataract patients. SETTING: One public hospital in the Netherlands. DESIGN: Prospective cohort study. METHODS: Resource use data were collected from a healthcare and societal perspective on the day of surgery. Other outcome parameters included pupil size, surgeon satisfaction, postoperative pain, and Catquest-9SF scores. RESULTS: Mean costs per patient were &OV0556; 506 in the ICMA group (n=122), &OV0556; 474 in the ocular insert group (n=115), and &OV0556; 451 in the topical group (n=131). The acquisition cost of ICMA was highest and resulted in longer surgical time. After correction for an imbalance in the distribution of fast and slow surgeons, mean costs in the ocular insert and topical groups were comparable (&OV0556; 450 versus &OV0556; 444). There was no difference in the use of additional mydriatics intraoperatively (P=0.521).The mean ratio of pupil size to white-to-white distance was lower in the ICMA group during all intraoperative measurements (P<0.001), but similar between the topical and ocular insert groups (P range 0.11-0.82). CONCLUSIONS: In the investigated setting in the Netherlands, ICMA was the most costly strategy. In addition, pupil size was lowest in the ICMA group, but did not result in more additional mydriasis measures intraoperatively. The ocular insert was comparable to topical mydriatics in regard to costs and pupil size. Implementation of ICMA could be considered when availability of nurses or physical space for perioperative care is limited
Prediabetes and Type 2 Diabetes Are Associated With Generalized Microvascular Dysfunction The Maastricht Study
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