Search results for "Coherence"
showing 10 items of 905 documents
OCT is not useful for detection of minimal diabetic retinopathy in type 1 diabetes.
2009
Optical coherence tomography (OCT) has been proven useful in measuring retinal thickness (RT) in patients with diabetes, although with discordant results in different studies. We examined RT in patients with type 1 diabetes (T1D) with or without minimal diabetic retinopathy (MDR) to test whether OCT is able to identify early retinal changes and potential correlations with metabolic parameters. RT of 102 patients with T1D (53 females, 49 males, aged 27.03 +/- 7.4 years) and of 42 healthy controls was examined, with analysis of nine different sectors (fovea, four pericentral and four peripheral sectors). According to the results of basal fundus photography, patients were divided into two grou…
Coronary embolism in a young patient with nonbacterial thrombotic endocarditis related to antiphospholipid syndrome
2020
myocardial infarction
Assessment of corneal thickness and tear meniscus during contact-lens wear
2014
To assess the effect of seven different daily disposable contact lenses upon corneal thickness, as well as upon tear meniscus volume, by using optical coherence tomography (OCT).Thirty-four young healthy subjects wore seven different types of daily disposable soft contact lenses, each for a period of 12h: Delefilcon A, Nelfilcon A, Omafilcon A, Filcon II3, Narafilcon A, Etafilcon A and Hilafilcon B. Central and mid-peripheral corneal thickness and lower tear meniscus volume (TMV) were measured using an OCT device during contact-lens wear at 4-h intervals throughout a 12-h period. Measurements were also recorded without any contact lenses being worn during a day.In the no-lens scenario a sma…
Comparison of partial coherence interferometry and ultrasound for anterior segment biometry.
2008
To assess the performance of a partial coherence interferometry (PCI)-based device for the determination of anterior segment biometry.Clinica Centrofama, Cartagena, Murcia, Spain.Central corneal thickness (CCT), anterior chamber depth (ACD), and lens thickness (LT) were measured with the ACMaster PCI anterior segment biometer and an Echoscan US-1800 ultrasound (US) biometer/pachymeter with and without cycloplegia. To determine the precision of the instruments, the same examiner took 30 consecutive CCT, ACD, and LT measurements in a single subject under the same conditions and with and without cycloplegia. The same measurements were performed in additional subjects.Twenty-one eyes (16 subjec…
Retinal Imaging through Phakic Iris-Claw IOL.
2014
AbstractBackground: Phakic anterior chamber iris-fixated IOL (PIOL) are established for the correction of high myopia. These patients require attention to macular pathologies. This study was to evaluate the quality of imaging through the PIOLs. Methods: 54 eyes of 31 myopic and hyperopic patients with Verisyse®, Verisyse toric®, and Veriflex® phakic iris-fixated IOL were included. Mean preoperative refraction was −11.0 D and +5.7 D, respectively; mean follow-up time was 7.4 years (5–11 years). A matched control group was formed without PIOL implantation. OCT scans were performed and evaluated qualitatively and quantitatively. Results: In 52 eyes of 31 patients (96%), a 3D-OCT image and fund…
Association between early-stage chronic kidney disease and reduced choroidal thickness in essential hypertensive patients.
2018
The introduction in the past few years of advanced optical coherence tomography (OCT) techniques has greatly increased our understanding of the choroid, which is the most important vascular layer of the eye. Our study aimed to assess choroidal thickness by using swept-source OCT (SS-OCT) in essential hypertensive patients (EHs) with and without early-stage chronic kidney disease (CKD). We enrolled 100 EHs, of whom 65 were without kidney damage, and 35 had stage 1-3 CKD. In all of the participants, SS-OCT and a routine biochemical workup were performed. Glomerular filtration rate (GFR) was estimated by the CKD Epidemiology Collaboration equation (eGFR). CKD was defined in agreement with the …
Avaliação por OCT in vivo do comprimentos axiais centrais do segmento anterior
2017
ABSTRACT Purpose: To assess changes in anatomic structures in the anterior eye segment in terms of axial lengths with accommodation via optical coherence tomography. Methods: In this observational study, 25 eyes of 25 healthy adults were examined using the Visante® omni optical coherence tomography system. Central corneal thickness, anterior chamber depth, central lens thickness, and anterior segment length were assessed. The evaluated parameters were obtained with accommodation using different stimulus vergences, namely 0.0, -1.0, -2.0, and -3.0 D. Variation of these parameters was compared among different levels of accommodation. Results: Central corneal thickness was not altered at any s…
Causal cross-spectral analysis of heart rate and blood pressure variability for describing the impairment of the cardiovascular control in neurally m…
2006
A causal approach to the calculation of coherence and transfer function between systolic pressure (SP) and RR interval variability was applied in eight patients and eight control subjects during prolonged tilt test for investigating the impairment of cardiovascular control related to neurally mediated syncope. The causal analysis showed a depressed baroreflex regulation in resting patients, with reduced gain and increased latency from SP to RR, and a drop of the baroreflex coupling immediately before syncope. These findings, which were not elicited by traditional cross-spectral analysis, strongly suggest the use of the causal approach for the study of syncope mechanisms. © 2006 IEEE.
Measuring postural-related changes of spontaneous baroreflex sensitivity after repeated long-duration diving: Frequency domain approaches
2012
Sustained water immersion is thought to modulate orthostatic tolerance to an extent dependent on the duration and repetition over consecutive days of the diving sessions. We tested this hypothesis investigating in ten healthy subjects the potential changes in the cardiovascular response to head-up tilt induced by single and multiple resting air dives. Parametric cross-spectral analysis of spontaneous RR interval and systolic arterial pressure variability was performed in three experimental sessions: before diving (BD), after single 6-hour dive (ASD), and after multiple 6-hour dives (AMD, 5 consecutive days with 18-hour surface interval). From this analysis, baroreflex sensitivity (BRS) was …
Exploring directionality in spontaneous heart period and systolic pressure variability interactions in humans: implications in the evaluation of baro…
2004
Although in physiological conditions RR interval and systolic arterial pressure (SAP) are likely to interact in a closed loop, the traditional cross-spectral analysis cannot distinguish feedback (FB) from feedforward (FF) influences. In this study, a causal approach was applied for calculating the coherence from SAP to RR ( Ks-r) and from RR to SAP ( Kr-s) and the gain and phase of the baroreflex transfer function. The method was applied, compared with the noncausal one, to RR and SAP series taken from 15 healthy young subjects in the supine position and after passive head-up tilt. For the low frequency (0.04–0.15 Hz) spectral component, the enhanced FF coupling ( Kr-s = 0.59 ± 0.21, signi…