Search results for "Corneal endothelium"
showing 10 items of 21 documents
Scheimpflug biometry of the anterior segment after implantation of foldable iris-fixated lenses.
2006
ABSTRACT PURPOSE: To evaluate intraocular dimensions of the anterior segment of myopic phakic eyes after implantation of foldable iris-fixated lenses. METHODS: Seventeen myopic eyes that received a foldable iris-fixated phakic intraocular lens (PIOL) were assessed. Distances between the cornea and the IOLoptic edge and between the IOL optic and the crystalline lens were evaluated using Scheimpf lug photography 3 months postoperatively. RESULTS: The average postoperative distance between the central corneal endothelium and the anterior surface of the IOL was 2.01±0.26 mm. The distance between the corneal endothelium and the peripheral edge of the IOL averaged 1.32±0.18 mm at the 12 o'clock p…
Effects of intraocular cefotaxime on the human corneal endothelium
2001
Abstract Purpose To ascertain whether 0.4 mL of cefotaxime 0.25% applied intracamerally causes toxic alteration of the human corneal endothelium. Methods In this prospective randomized masked study, 66 patients had cataract extraction using phacoemulsification, a frown incision, and implantation of a poly(methyl methacrylate) intraocular lens. This was followed by intraocular injection of 0.4 mL of cefotaxime 0.25% or balanced salt solution (BSS®). Contact specular microscopy and photography were performed preoperatively and 1 to 4 days and 3 months postoperatively. Results In the cefotaxime group, the mean endothelial cell count was 2729 cells/mm 2 ± 474 (SD) preoperatively, 2520 ± 462 cel…
Effects of LASIK on Corneal Endothelium Using the 15-kHz IntraLase Femtosecond Laser
2011
PURPOSE: To assess the effects of LASIK with the 15-kHz IntraLase femtosecond laser on corneal endothelium. METHODS: In a prospective, single-center clinical trial, 138 patients (mean age: 32.0±7.1 years [range: 21 to 42 years]) underwent femtosecond LASIK for the correction of myopia −0.75 to −9.00 diopters (D) and cylinder up to 3.25 D. Patients were divided into two groups: contact lens group (n=76) and non-contact lens group (n=62). Pre- and 12-month postoperative specular microscopy of the central corneal endothelium was performed. The integrity of the central endothelium was assessed in terms of endothelial cell density and percentage of hexagonality. RESULTS: In the contact lens gro…
Granulometric moments and corneal endothelium status
2001
Abstract Specular microscopy is a common practice in Ophthalmology. The corneal endothelium status is usually evaluated by means of the density, the hexagonality, the mean, the standard deviation and the coefficient of variation of cell areas. We propose to replace the cell area moments by the corresponding moments of a different probability distribution, the granulometric size distribution associated to a disc. All cells touching the frame are ignored by the area moments but used by the granulometric moments. Twenty images have been analyzed. When the size of the focused region is reduced, the area moments show a greater variation than the corresponding granulometric moments.
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).
MORPHOMETRIC ANALYSIS OF HUMAN CORNEAL ENDOTHELIUM BY MEANS OF SPATIAL POINT PATTERNS
2002
This paper presents a method for detecting abnormalities in spatial arrangements of cells within any tissue that can be described by different sets of relevant points. The method has been applied to the detection of subtle abnormalities in corneal endothelia. Images of this type of tissue can be characterized by two types of points: cell centroids and triple points associated with the apical intersections as it was proposed by Díaz.7 Both types of points jointly considered are modeled using a bivariate spatial point process; then a statistical analysis based on certain distributional descriptors proposed by Doguwa4,9 is carried out to discriminate severe and subtle abnormalities from contr…
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…