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Cornea spatial profile

Cynthia J Roberts, Ashraf M Mahmoud, Jeffrey P Bons, Arif Hossain, Ahmed Elsheikh, Riccardo Vinciguerra, Paolo Vinciguerra, Renato Ambrósio
PURPOSE: To investigate two new stiffness parameters and their relationships with the dynamic corneal response (DCR) parameters and compare normal and keratoconic eyes. METHODS: Stiffness parameters are defined as Resultant Pressure at inward applanation (A1) divided by corneal displacement. Stiffness parameter A1 uses displacement between the undeformed cornea and A1 and stiffness parameter highest concavity (HC) uses displacement from A1 to maximum deflection during HC...
April 1, 2017: Journal of Refractive Surgery
Ying Chen, James V Jester, David M Anderson, Satori A Marchitti, Kevin L Schey, David C Thompson, Vasilis Vasiliou
ALDH3A1 is a corneal crystallin that protects ocular tissues from ultraviolet radiation through catalytic and non-catalytic functions. In addition, ALDH3A1 plays a functional role in corneal epithelial homeostasis by simultaneously modulating proliferation and differentiation. We have previously shown that Aldh3a1 knockout mice in a C57B6/129sV mixed genetic background develop lens cataracts. In the current study, we evaluated the corneal phenotype of Aldh3a1 knockout mice bred into a C57B/6J congenic background (KO)...
October 1, 2017: Chemico-biological Interactions
Nandor Bekesi, Carlos Dorronsoro, Andrés de la Hoz, Susana Marcos
OBJECTIVE: To validate a new method for reconstructing corneal biomechanical properties from air puff corneal deformation images using hydrogel polymer model corneas and porcine corneas. METHODS: Air puff deformation imaging was performed on model eyes with artificial corneas made out of three different hydrogel materials with three different thicknesses and on porcine eyes, at constant intraocular pressure of 15 mmHg. The cornea air puff deformation was modeled using finite elements, and hyperelastic material parameters were determined through inverse modeling, minimizing the difference between the simulated and the measured central deformation amplitude and central-peripheral deformation ratio parameters...
2016: PloS One
Henryk Kasprzak, Agnieszka Boszczyk
The paper presents numerical analysis of corneal curvature distribution, based on Corvis ST images. It was shown that a new approach to analysis of corneal curvature from tonometer images enables a better description and understanding of processes during fast corneal deformation. Ten healthy volunteers participated in nine repeated measurements on one eye. 90 sequences of images were processed with software written in Matlab, with the use of the Image Processing Toolbox. Time-spatial distribution of the local curvature distribution of the corneal profile was obtained for each and every measurement...
May 2016: Journal of Biophotonics
Nandor Bekesi, Irene E Kochevar, Susana Marcos
PURPOSE: To compare the biomechanical corneal response of two different corneal cross-linking (CXL) treatments, rose bengal-green light (RGX) and riboflavin-UVA (UVX), using noninvasive imaging. METHODS: A total of 12 enucleated rabbit eyes were treated with RGX and 12 with UVX. Corneal dynamic deformation to an air puff was measured by high speed Scheimpflug imaging (Corvis ST) before and after treatment. The spatial and temporal deformation profiles were evaluated at constant intraocular pressure of 15 mm Hg, and several deformation parameters were estimated...
March 2016: Investigative Ophthalmology & Visual Science
Xueying Zhou, Lin Wang, Renyuan Chu, Zhiqiang Yu
OBJECTIVE: To explore the distribution of relational corneal thickness parameters including central corneal thickness (CCT), thinnest pachymetry (TP), cornea thickness spatial profile (CTSP), percentage thickness increase (PTI), pachymetric progression index (PPI) and Ambrósio's relational thickness (ART) in the normal population, and their relationships with corneal astigmatism and curvature. METHODS: A total of 1 203 eyes from 1 203 normal outpatients were enrolled in this cross-sectional study...
September 2014: [Zhonghua Yan Ke za Zhi] Chinese Journal of Ophthalmology
Eloy A Villegas, Encarna Alcon, Elena Rubio, José M Marín, Pablo Artal
PURPOSE: To evaluate efficacy, predictability, and stability of refractive treatments using light-adjustable intraocular lenses (IOLs). SETTING: University Hospital Virgen de la Arrixaca, Murcia, Spain. DESIGN: Prospective nonrandomized clinical trial. METHODS: Eyes with a light-adjustable IOL (LAL) were treated with spatial intensity profiles to correct refractive errors. The effective changes in refraction in the light-adjustable IOL after every treatment were estimated by subtracting those in the whole eye and the cornea, which were measured with a Hartmann-Shack sensor and a corneal topographer, respectively...
July 2014: Journal of Cataract and Refractive Surgery
Kazutaka Kamiya, Rie Ishii, Kimiya Shimizu, Akihito Igarashi
AIM: To evaluate corneal elevation, pachymetry and keratometry in keratoconic eyes according to the clinical stage of the disease. METHODS: This prospective comparative study was performed on one hundred and twenty-six eyes of 83 patients who had keratoconus, and 42 normal eyes of 42 age-matched subjects. Corneal elevation, pachymetry and keratometry were measured using a rotating Scheimpflug camera (Pentacam HR, Oculus) in these eyes. The area under the receiver operating characteristic (AUROC) curves was used to analyse the diagnostic significance of these parameters, with respect to each stage of Amsler-Krumeich classifications...
April 2014: British Journal of Ophthalmology
Jens Bühren, Thomas Schäffeler, Thomas Kohnen
PURPOSE: To validate the discriminative ability of wavefront- and pachymetry-based corneal topographic metrics to detect subclinical keratoconus in a new patient collective. SETTING: Department of Ophthalmology, Goethe-University, Frankfurt am Main, Germany. DESIGN: Retrospective cross-sectional study. METHODS: Normal fellow eyes with early keratoconus and preoperative eyes with an uneventful follow-up without signs of iatrogenic keratectasia 12 months after laser in situ keratoconus were included...
February 2014: Journal of Cataract and Refractive Surgery
Sabine Kling, Susana Marcos
PURPOSE: Air puff systems have been presented recently to measure corneal biomechanical properties in vivo. In our study we tested the influence of several factors on corneal deformation to an air puff: IOP, corneal rigidity, dehydration, presence of sclera, and in vivo versus in vitro conditions. METHODS: We used 14 freshly enucleated porcine eyes and five human donor eyes for in vitro experiments; nine human eyes were used for in vivo experiments. Corneal deformation was studied as a function of: IOP ranging from 15 to 45 mm Hg (in vitro); dehydration after riboflavin-dextran instillation (in vitro); corneal rigidity after standard ultraviolet (UV) corneal crosslinking (CXL, in vitro); boundary conditions, that is effect of the presence of the sclera (comparing corneal buttons and whole globes in vitro in pigs); and effect of ocular muscles (comparing human whole globes in vitro and in vivo)...
July 26, 2013: Investigative Ophthalmology & Visual Science
Chris Bath
Corneal epithelium is being regenerated throughout life by limbal epithelial stem cells (LESCs) believed to be located in histologically defined stem cell niches in corneal limbus. Defective or dysfunctional LESCs result in limbal stem cell deficiency (LSCD) causing pain and decreased visual acuity. Since the first successful treatment of LSCD by transplantation of ex vivo expanded LESCs in 1997, many attempts have been carried out to optimize culture conditions to improve the outcome of surgery. To date, progress in this field of bioengineering is substantially hindered by both the lack of specific biomarkers of LESCs and the lack of a precise molecular characterization of in situ epithelial subpopulations...
June 2013: Acta Ophthalmologica
Ithar M Beshtawi, Riaz Akhtar, M Chantal Hillarby, Clare O'Donnell, Xuegen Zhao, Arun Brahma, Fiona Carley, Brian Derby, Hema Radhakrishnan
PURPOSE: To assess the feasibility of applying scanning acoustic microscopy (SAM) on UV cross-linked corneal tissue for mapping and analyzing its biomechanical properties. MATERIALS AND METHODS: Five corneal pairs (10 corneas) were used. In each pair, one cornea was cross-linked (epithelium removed, riboflavin application for 45 min and UVA irradiation for 30 min) and the contralateral control cornea was epithelial debrided and treated only with riboflavin for 45 min...
April 2013: Current Eye Research
Sho C Takatori, Clayton J Radke
PURPOSE: Because neither the human cornea nor a soft contact lens (SCL) is of constant thickness, corneal oxygenation varies locally. To quantify the importance of cornea/SCL thickness variations on oxygen demand, we develop a quasi-2-dimensional (2D) respiration model that accounts for aerobic and anaerobic metabolism and bicarbonate buffering. METHODS: Because metabolism is critical to oxygen demand, we extend the 1-dimensional (1D), 6-layer oxygen metabolic model of Chhabra et al...
April 2012: Cornea
S Reiss, O Stachs, R Guthoff, H Stolz
The confocal Brillouin spectroscopy is an innovative measurement method that allows the non-invasive determination of the rheological properties of materials. Its application in ophthalmology can offer the possibility to determine in-vivo the deformation properties of sections of transparent biological tissue such as the cornea or eye lens with spatial resolution. This seems to be a promising approach concerning current presbyopia research. Due to the spatially resolved detection of the viscoelastic lens properties, a better understanding of the natural aging process of the lens and the influences of different lens opacities on the stiffness is expected...
December 2011: Klinische Monatsblätter Für Augenheilkunde
Giuliano Scarcelli, Roberto Pineda, Seok Hyun Yun
PURPOSE: The mechanical properties of corneal tissue are linked to prevalent ocular diseases and therapeutic procedures. Brillouin microscopy is a novel optical technology that enables three-dimensional mechanical imaging. In this study, the feasibility of this noncontact technique was tested for in situ quantitative assessment of the biomechanical properties of the cornea. METHODS: Brillouin light-scattering involves a spectral shift proportional to the longitudinal modulus of elasticity of the tissue...
January 20, 2012: Investigative Ophthalmology & Visual Science
Fritz H Hengerer, H Burkhard Dick, Simone Buchwald, Werner W Hütz, Ina Conrad-Hengerer
PURPOSE: To determine quantitative changes in endothelial cell loss and corneal thickness in patients having cataract surgery and implantation of a light-adjustable intraocular lens (IOL) to correct residual postoperative refractive errors by application of a spatially profiled near-ultraviolet (UV) light. SETTING: Ruhr University Eye Clinic, Bochum, Germany. DESIGN: Cohort study. METHODS: The light-adjustable IOLs were implanted after phacoemulsification cataract surgery and treated with spatial-intensity-profiled UV light at 365 nm to induce a targeted refractive change...
December 2011: Journal of Cataract and Refractive Surgery
Jeannette Beckman Rehnman, Chris C Janbaz, Anders Behndig, Christina Lindén
PURPOSE: To assess the spatial distribution and time course of increased corneal light scattering after corneal collagen crosslinking (CXL) with riboflavin and ultraviolet-A irradiation. SETTING: Umeå University Hospital Eye Clinic, Umeå, Sweden. DESIGN: Case series. METHODS: Eyes with keratoconus were examined with Scheimpflug photography before and 1 and 6 months after CXL. Corneal light scattering was quantified throughout the corneal thickness at 8 measurement points 0...
November 2011: Journal of Cataract and Refractive Surgery
Mario Shraiki, Samuel Arba-Mosquera
PURPOSE: To evaluate ablation algorithms and temperature changes in laser refractive surgery. METHODS: The model (virtual laser system [VLS]) simulates different physical effects of an entire surgical process, simulating the shot-by-shot ablation process based on a modeled beam profile. The model is comprehensive and directly considers applied correction; corneal geometry, including astigmatism; laser beam characteristics; and ablative spot properties. RESULTS: Pulse lists collected from actual treatments were used to simulate the temperature increase during the ablation process...
May 2011: Investigative Ophthalmology & Visual Science
Abhijit Sinha Roy, William J Dupps
The purpose of this study is to develop a 3D patient-specific finite element model (FEM) of the cornea and sclera to compare predicted and in vivo refractive outcomes and to estimate the corneal elastic property changes associated with each procedure. Both eyes of a patient who underwent laser-assisted in situ keratomileusis (LASIK) for myopic astigmatism were modeled. Pre- and postoperative Scheimpflug anterior and posterior corneal elevation maps were imported into a 3D corneo-scleral FEM with an unrestrained limbus...
January 2011: Journal of Biomechanical Engineering
Marianthi Karali, Ivana Peluso, Vincenzo A Gennarino, Marchesa Bilio, Roberta Verde, Giampiero Lago, Pascal Dollé, Sandro Banfi
BACKGROUND: MicroRNAs (miRNAs) are key regulators of biological processes. To define miRNA function in the eye, it is essential to determine a high-resolution profile of their spatial and temporal distribution. RESULTS: In this report, we present the first comprehensive survey of miRNA expression in ocular tissues, using both microarray and RNA in situ hybridization (ISH) procedures. We initially determined the expression profiles of miRNAs in the retina, lens, cornea and retinal pigment epithelium of the adult mouse eye by microarray...
December 20, 2010: BMC Genomics
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