157 research outputs found

    Comparison of average epithelial thicknesses for keratoconic and healthy astigmatic eyes.

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    <p>Top: Cross-sectional steepest-meridional average epithelial thicknesses for keratoconic and healthy astigmatic eyes. Bottom: Cross-sectional flattest-meridional average epithelial thicknesses for keratoconic and healthy astigmatic eyes.</p

    Comparison of Corneal Epithelial and Stromal Thickness Distributions between Eyes with Keratoconus and Healthy Eyes with Corneal Astigmatism ≥2.0 D

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    <div><p>Purpose</p><p>To identify corneal epithelial- and stromal-thickness distribution patterns in keratoconus using spectral-domain optical coherence tomography (SD-OCT).</p><p>Patients and Methods</p><p>We analyzed SD-OCT findings in 20 confirmed cases of keratoconus (group 1) and in 20 healthy subjects with corneal astigmatism ≥2 D (group 2). Epithelial and stromal thicknesses were measured at 11 strategic locations along the steepest and flattest meridians, previously located by corneal topography. Vertical mirrored symmetry superimposition was used in the statistical analysis.</p><p>Results</p><p>The mean maximum keratometry measurements in groups 1 and 2 were 47.9±2.9 D (range, 41.8–52.8) and 45.6±1.1 D (range, 42.3–47.5), respectively, with mean corneal cylinders of 3.3±2.2 D (range, 0.5–9.5) and 3.6±1.2 D (range, 2.0–6.4), respectively. The mean epithelial thickness along the steepest meridian in group 1 was the lowest (37.4±4.4 µm) at 1.2 mm inferotemporally and the highest (59.3±4.4 µm) at 1.4 mm supranasally from the corneal vertex. There was only a small deviation in thickness along the steepest meridian in group 2, as well as along the flattest meridians in both groups. The stromal thickness distribution in the two groups was similar to the epithelial, while the stromal thickness was generally lower in group 1 than in group 2.</p><p>Conclusions</p><p>SD-OCT provides details about the distribution of corneal epithelial and stromal thicknesses. The epithelium and stroma in keratoconic eyes were thinner inferotemporally and thicker supranasally compared with control eyes. The distribution pattern was more distinct in epithelium than in stroma. This finding may help improve the early diagnosis of keratoconus.</p><p>Trial Registration</p><p>ClinicalTrials.gov <a href="http://clinicaltrials.gov/ct2/show/study/NCT02023619?term=NCT02023619&rank=1" target="_blank">NCT02023619</a></p></div

    Topographic maps of the average epithelial and stromal thicknesses for keratoconic eyes and healthy eyes.

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    <p>The color scale represents the thickness in µm; I = inferior; N = nasal; S = superior; T = temporal.</p

    Epithelial and Stromal Thickness With Keratoconus and Controls (Mean±Standard Deviation).

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    <p>For steepest meridian, “−” represents inferior to corneal vertex, “+” represents superior to corneal vertex. For flattest meridian, “−” represents temporal to corneal vertex, “+” represents nasal to corneal vertex.</p

    Corneal elevation topography and corneal optical coherence tomography (OCT) images.

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    <p>Anterior corneal elevation topography and cross-sectional corneal optical coherence tomography (OCT) images at the steepest (A, C) and flattest meridians (B, D) were taken for one keratoconic eye and one healthy eye with high corneal astigmatism.</p

    Recognition performance of CEERM, based on rules and SVM.

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    <p>Recognition performance of CEERM, based on rules and SVM.</p

    Threshold analysis of dynamic supervised classifier.

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    <p>Threshold analysis of dynamic supervised classifier.</p

    Unsupervised CEERM recognition performance based on different feature layers.

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    <p>Unsupervised CEERM recognition performance based on different feature layers.</p

    Production of Hydrocarbon Fuel Using Two-Step Torrefaction and Fast Pyrolysis of Pine. Part 1: Techno-economic Analysis

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    As part I of two companion papers, the present paper evaluates the economic feasibility of hydrocarbon biofuel production via two pathways: a one-step production pathway through fast pyrolysis of biomass followed by the catalytic upgrade of bio-oil to a liquid hydrocarbon biofuel and a novel two-step pathway that includes a torrefaction pretreatment step prior to fast pyrolysis and then the catalytic upgrade. These two pathways were modeled using Aspen Plus to process 1000 dry metric tons/day of feed through the fast pyrolysis unit operating at 530 °C whereas torrefaction for the two-step pathway was investigated at three different torrefaction temperatures of 290, 310, and 330 °C. Three scenarios of producing process heat from natural gas, internal byproducts biochar supplemented with natural gas, and torrefaction condensate were investigated, with additional heat integration considered. Minimum selling price ranged from 4.01/galto4.01/gal to 4.78/gal for the heat-integrated processes whereas the price ranged from 4.70/galto4.70/gal to 6.84/gal without heat integration. Analysis indicated that a one-step pathway and a two-step pathway with torrefaction taking place at 290 °C yielded comparable least minimum selling price and it increased with increasing torrefaction temperature. Sensitivity analysis showed that the yield of hydrocarbon biofuel, total project investment, and internal rate of return have the greatest impact