Search results for "Genetic Structures"
showing 10 items of 2107 documents
CT AND MRI OF THYROGLOSSAL DUCT CYST
2015
Aims and objectives Methods and materials Results Conclusion Personal information References
Anatomic variants of the biliary tree at MRCP: still too rarely reported!
2015
Aims and objectives Methods and materials Results Conclusion Personal information References
Repeatability of in vitro power profile measurements for multifocal contact lenses
2015
Abstract Purpose To evaluate the repeatability of an optical device (NIMO TR1504, Lambda-X, Belgium) for measuring multifocal contact lens power profiles. Methods The NIMO TR1504 was used to measure power profiles 30 times for each of 10 different contact lenses from 4 major companies. All contact lenses were labelled as −3 D for distance vision; half were for high addition and half for low addition. The optical zone in all measurements was set to 3-mm radius. For each lens, the median power profile and the residuals of the 30 measurements were calculated. The 95% confidence bands and two indices that summarize measurement errors were calculated: the repeatability limit and an index of repe…
“In situ” corneal and contact lens thickness changes with high resolution OCT
2012
Purpose: To show the utility of high resolution spectral domain optical coherence tomography (HR SOCT) for the in situ evaluation of epithelial, stromal and contact lens (CL) thickness changes under closed-eye conditions without lens removal. Settings: Clinical and Experimental Optometry Research Lab, University of Minho, Portugal. Methods: Eight young healthy patients wore a thick soft CL during 90 minutes under closed-eye conditions and measures of epithelial and stromal corneal thickness were obtained at regular intervals using a HR SOCT (Copernicus HR, Optopol Tech. SA, Poland). Results: Minimal changes in epithelial thickness were detected with a transient statistically significant inc…
Early and late clinical landmarks of corneal dystrophies
2020
Abstract Corneal dystrophies (CDs) represent a heterogenous group of genetic diseases (Lisch and Weiss, 2019). The International Committee of Classification of Corneal Dystrophies (IC3D) distinguishes between 22 distinct forms of corneal dystrophy (CD) which are predominantly autosomal dominant, although autosomal recessive and X-chromosomal dominant and recessive patterns do exist. A detailed corneal examination of as many affected family members as possible can show the phenotypic differences of the various generations. There are few publications which describe the different CDs with regard to the early and late phenotypes. According to early and late phenotype, three types of CD are gene…
Granulometric analysis of corneal endothelium specular images by using a germ–grain model
2007
Specular microscopy is widely used to study the human corneal endothelium status in vivo. In this paper, the corneal endothelium is represented as a binary image composed of the cell inscribed circles. The granulometric distribution function of the complement of this image is used as a functional descriptor, which provides information about the shape, size and spatial arrangement of cells. Experimental evaluation using bootstrap techniques shows its ability to discriminate between controls and pathological cases. It represents a reliable and graphical alternative to the classical indices (cell density, hexagonality and coefficient of variation of cell areas), which behave poorly when detect…
Corneal Oxygen Supply Conditions
1976
Pronounced cornea hypoxia induces swelling and a loss of transparency. Hypoxia of longer duration causes necrosis, particularly of the corneal endothelium. These findings were observed after ligation of the cilial arteries and the arteria carotis interna, after reduction of oxygen tension on the anterior corneal surface as well as after prolonged wearing of ill-fitted contact lenses (11, 15, 18, 22, 23). Because the normal function of the corneal endothelium plays a central role in maintaining transparency, an insufficient endothelial oxygen supply can directly influence vision (3, 17).
A granulometric analysis of specular microscopy images of human corneal endothelia
2005
The inner layer of the human cornea, called the corneal endothelium, plays an important role in the maintenance of corneal transparency. Specular microscopy is the most widely used technique to study the corneal endothelium in vivo. Improvements in technology have allowed us to obtain good quality specular images, but the detection and quantification of small size-shape cell changes is not obvious, specially when the physician wants to evaluate endothelial cell changes after some surgical procedures. This paper proposes a methodology to analyze specular microscopy images. Every corneal endothelium is described by means of different cumulative distribution functions or some moments (mean, st…
Measuring the Spatial Homogeneity in Corneal Endotheliums by Means of a Randomization Test
1999
Quantification of regularity of cell sizes and the spatial arrangement of cells in corneal endotheliums becomes of a great importance associated to stress situations such as cataract surgery, corneal transplantation or implantation of intra-ocular lenses. A new index of regularity of the spatial distribution of cell sizes in corneal endotheliums is proposed. The corneal endothelium is described by means of a spatial marked point pattern (the cell centroids marked with the cell areas). The hypothesis of no dependency between mark and locations is tested by a Monte Carlo test. The new index is the p-value of the test validating the hypothesis. Pairs of endotheliums from different eyes of the …
Classifying human endothelial cells based on individual granulometric size distributions
2002
Abstract This paper presents an application to a medical problem of methods of shape analysis based on mathematical morphology. The medical problem consists on the detection of abnormalities in the corneal endothelium, a tissue composed by quasi-planar cells of ideally regular hexagonal shape. Images of this tissue are taken by a specular microscope and used to evaluate the corneal endothelium status. Up to now, cell density, hexagonality and an analysis of cell areas are the usual descriptors of a corneal endothelium. These parameters are not sensitive enough to detect subtle lesions. What this paper proposes is an analysis based on granulometries, which are size-shape descriptors widely u…