Mean Coefficient Of Repeatability Research Articles

Repeatability and reproducibility of tear meniscus parameters measured by RTVue Fourier-domain optical coherence tomography

Background Tear meniscus gained by OCT device is essential to the dry eye diagnosis.Currently,RTVue Fourier-domain optical coherence tomography (FD-OCT) is commercially available to image the tear menisci.However,there were few studies to report the repeatability and reproducibility of lower and upper tear meniscus parameters measured by RTVue FD-OCT.Objective The purpose of this study was to assess the repeatability and reproducibility of lower and upper tear meniscus parameters measured by RTVue FD-OCT in normal and dry eyes.Methods In this prospective study,20 dry eyes of 20 patients were finally recruited,and 20 normal eyes of 20 age-and gender-matched healthy subjects were included during the same period.Successive three-time scans were performed at a 3-minute interval with RTVue FD-OCT in optional eye by one well-trained examiner,and the other operator performed the same measurement 10-15 minutes later.Six parameters of tear meniscus were yielded by custom software,including upper meniscus curvature (UMC),upper meniscus height(UMH),upper meniscus area (UMA),lower meniscus curvature (LMC),lower meniscus height (LMH) and lower meniscus area (LMA).The between-image repeatability was assessed using mean coefficient of repeatability (MCOR),while between-operator reproducibility were evaluated using coefficient of repeatability (COR) and interclass correlation of coefficients (ICC).Results As for the between-image repeatability,the results of MCOR for UMH,UMA,LMH and LMA were 5.11％,3.58％,4.98％ and 4.82％ respectively in the normal eyes and 5.60％,5.80％,5.03％ and 5.74％ respectively in the dry eyes.As for the between-operator reproducibility,the results of COR and ICC for UMA were 5.38％ and O.975,the COR and ICC for LMA were 5.28％ and 0.961 respectively in the normal eyes,and the results of COR and ICC for LMA were 9.69％ and 0.964 in the dry eyes.Conclusions The UMA,LMH and LMA tear meniscus parameters obtained by RTvue FD-OCT show good between-image repeatability,and LMA also presents good between-operator reproducibility.Measurement of tear meniscus parameters with RTVue FD-OCT measuring is a potential diagnostic index for the diagnosis of dry eye. Key words: Optical coherence tomography; Dry eye; Tear meniscus; Repeatability; Reproducibility

Variability and repeatability of quantitative, Fourier-domain optical coherence tomography Doppler blood flow in young and elderly healthy subjects.

The purpose of this study was to determine the within-session variability and between-session repeatability of spectral Fourier-domain optical coherence tomography (Doppler FD-OCT) Doppler retinal blood flow measurements in young and elderly subjects. Doppler FD-OCT blood flow was measured using the RTVue system. One eye of each of 20 healthy young (24.7 ± 2.7 years) and 16 healthy elderly (64.6 ± 5.1 years) subjects was randomly selected, and the pupil was dilated. The double circular scanning pattern of the RTVue was employed. Six Doppler FD-OCT measurements (i.e., each separate measurement comprising an upper and a lower nasal pupil scan) were acquired at each session. Measurements were repeated approximately 2 weeks later. Total retinal blood flow was calculated by summing flow from all detectable venules surrounding the optic nerve head. The coefficient of variation (COV) and coefficient of repeatability (COR) were calculated for each individual. The individual COVs for retinal blood flow for young subjects ranged from 0.4% to 20.4% (median 7.5%) and for the elderly subjects ranged from 0.6% to 34.6% (median 9.2%). The group mean CORs for retinal blood flow for young participants were 6.4 μL/min (median 5.91 μL/min, relative to a mean effect 39.8 μL/min) and for elderly subjects were 10.5 μL/min (median 9.2 μL/min, relative to a mean effect 46.4 μL/min). Doppler FD-OCT gave consistent and repeatable blood flow measurements within retinal venules in normal subjects. Considering the individual variation in blood flow measurements, confidence limits for retinal hemodynamics need to be determined on an individual basis.

Repeatability of Pachymetry and Thinnest Point Localization Using a Fourier-Domain Optical Coherence Tomographer

To evaluate the repeatability of pachymetry measures at six distinct locations using a Fourier-domain optical coherence tomographer. The location of the thinnest point was also described using vector analysis, and repeatability of the localization of the thinnest point was calculated. The right eye of 25 healthy subjects had 3 images of their right cornea captured using the pachymetry protocol and anterior segment lens of a commercially available Fourier-domain optical coherence tomographer (RTVue-100, Optovue, Fremont, CA). The first two images were used to quantify repeatability in the central (2 mm) and paracentral (2-5 mm) cornea. Cartesian coordinates representing the location of the thinnest point were used to determine the mean location in relation to the central cornea. Mean central thickness was 536.8 ± 31.1 μm, and the mean minimum thickness was 526.4 ± 33.1 μm. The thickest paracentral zone was the superior cornea and the thinnest was the temporal cornea. Intraclass correlation values ranged between 0.969 and 0.996, and the mean coefficient of repeatability was 1.74% across all locations evaluated. The thinnest point was located in the inferior temporal region in 80% of eyes and was an average distance of 1.01 mm from the corneal apex, subtending an angle of 26.7° from the horizontal. The RTVue-100 provides a highly repeatable measure of corneal thickness at various locations. The instrument is capable of describing and consistently duplicating the location of the thinnest point of the cornea; however, further comparative work with other clinical imaging modalities is required.

Objective measurement of intraocular forward light scatter using Hartmann-Shack spot patterns from clinical aberrometers: Model-eye and human-eye study

To apply software-based image-analysis tools to objectively determine intraocular scatter determined from clinically derived Hartmann-Shack patterns. Aston Academy of Life Sciences, Aston University, Birmingham, United Kingdom, and Department of Optics, University of Valencia, Valencia, Spain. Purpose-designed image-analysis software was used to quantify scatter from centroid patterns obtained using a clinical Hartmann-Shack analyzer (WASCA, Zeiss/Meditec). Three scatter values, as the maximum standard deviation within a lenslet for all lenslets in the pattern, were obtained in 6 model eyes and 10 human eyes. In the model-eye sample, patterns were obtained in 4 sessions: 2 without realigning between measurements, 1 with realignment, and 1 with an angular shift of 6 degrees from the instrument axis. Three measurements were made in the human eyes with the C-Quant straylight meter (Oculus) to obtain psychometric and objective measures of retinal straylight. Analysis of variance, intraclass correlation coefficients, coefficient of repeatability (CoR), and correlations were used to determine intrasession and intersession repeatability and the relationship between measures. No significant differences were found between the sessions in the model eye (P=.234). The mean CoR was less than 10% in all model- and human-eye sessions. After incomplete patterns were removed, good correlation was achieved between psychometric and objective scatter measurements despite the small sample size (n=6; r=-0.831; P=.040). The methodology was repeatable in model and human eyes, strong against realignment and misalignment, and sensitive. Clinical application would benefit from effective use of the sensor's dynamic range.

Repeatability of successive measurements with a portable nitric oxide analyser in patients with suggested or diagnosed asthma

The objective of our study was to determine the repeatability of successive measurements of exhaled nitric oxide (NO) with a portable device (NIOX MINO®). We assembled a sample of 332 pairs of repeated NO measurements acquired in the same session. The mean of the two successive measurements varied from 4.0 to 279.5 parts per billion (ppb). The mean coefficient of repeatability (CoR) of the entire study sample was 2.4 ppb. The difference between paired measurements increased slightly with increasing fractional exhaled nitric oxide (FENO); for the mean FENO of 24.0 ppb the calculated CoR was 2.2 and for the FENO of 54 ppb it was 3.2 ppb. The difference between paired observations for FENO values <50 ppb was significantly lower than that for values >50 ppb (p<0.001). The demonstrated repeatability of successive measurements with the device supports the view that, when the exhalation manoeuvre is technically valid and FENO is within normal limits, repeated determinations of FENO are generally not necessary for screening. In other cases, the mean value of two successive measurements would represent a more reliable measurement result.

Variability and repeatability of retinal blood flow measurements using the Canon laser blood flowmeter

The purpose of this work was to determine the within-session variability and between-session repeatability of the Canon Laser Blood Flowmeter (CLBF), Model 100, an instrument that permits the noninvasive measurement of retinal blood flow. The CLBF calculates flow in μl/min based on the Poiseuille principle. One eye of 20 normal subjects (mean age 36.5; SD 9.7 years) was randomly chosen. A minimum of five measurements was acquired of a temporal arteriole approximately 1 disc diameter from the optic nerve. Measurements were repeated within a 1-month period. Blood pressure and intraocular pressure were measured. The coefficient of variation (COV) and the coefficient of repeatability (COR) were calculated for each individual. The individual COVs for diameter, velocity, and flow ranged from 0.5 to 6.5% (median 2.0%), 4.8 to 39.7% (median 19.9%), and 4.8 to 37.3% (median 19.3%), respectively. The group mean CORs for diameter, velocity, and flow were 5.2 μm (relative to a mean effect of 104.6 μm), 8.8 mm/s (relative to a mean effect of 33.9 mm/s), and 2.6 μl/min (relative to a mean effect of 8.8 μl/min), respectively. The CLBF gave consistent and repeatable measurements of blood flow within retinal arterioles in normal subjects. Given the range of individual variation in the velocity measurement, and thus flow, confidence limits for retinal hemodynamics need to be determined on an individual basis.