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Corneal Biomechanics

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https://www.readbyqxmd.com/read/28337056/normative-values-and-contralateral-comparison-of-anterior-chamber-parameters-measured-by-pentacam-and-its-correlation-with-corneal-biomechanical-factors
#1
Mohammad Reza Sedaghat, Vahid Mohammad Zadeh, Kaveh Fadakar, Sakineh Kadivar, Mojtaba Abrishami
PURPOSE: To evaluate the normative values of anterior chamber parameters measured by Pentacam and corneal hysteresis (CH) and corneal resistance factor (CRF) measured by Ocular Response Analyzer (ORA) and their relationship. METHODS: In an observational cross-sectional study, patients aged 18-35 years were included. Exclusion criteria were history of any intraocular or corneal disease, anomaly or surgery; hyperopic spherical refraction more than +3, and myopic spherical refraction less than -5...
January 2017: Saudi Journal of Ophthalmology: Official Journal of the Saudi Ophthalmological Society
https://www.readbyqxmd.com/read/28320557/study-of-light-scattering-using-c-quant-%C3%A2-in-patients-with-fuchs-endothelial-dystrophy-a-pilot-study
#2
B Castaño-Martín, J Gros-Otero, J Martínez, M Teus
OBJECTIVE: The purpose of this study was to determine the light scattering in patients with Fuchs' endothelial dystrophy without clinically significant corneal oedema, and evaluate its relationship with endothelial cell count, corneal thickness, and corneal biomechanical parameters. MATERIALS AND METHODS: The values of light scattering were measured by C-Quant(®) (Oculus Optikgeräte GmbH, Germany) in 32 eyes of 17 patients diagnosed with Fuchs' endothelial dystrophy without clinically significant corneal oedema...
March 17, 2017: Archivos de la Sociedad Española de Oftalmología
https://www.readbyqxmd.com/read/28316192/-effect-of-optical-zone-diameter-on-corneal-biomechanical-properties-after-small-incision-lenticule-extraction
#3
P H Wei, Y Wang, H Li, R Dou, L Y Li, W Zhao, J M Zhang
Objective: To investigate the effect of optical zone diameter on corneal biomechanical properties after small incision lenticule extraction (SMILE). Methods: In this prospective case-control study, 62 eyes of 42 patients with myopia and myopic astigmatism that had undergone SMILE procedure were divided into 2 groups according to the optical zone (OZ) diameter: group A, 31 eyes of 19 patients, OZ= 6.5 mm; group B, 31eyes of 23 patients, OZ=6.0 mm. These patients were examined for corneal hysteresis (CH) and corneal resistance factor (CRF) with the Ocular Response Analyzer (ORA) preoperatively and at 1 week, 1 month and 3 months postoperatively; at the same time, the central corneal thickness-corrected indices of DifCH and DifCRF were calculated...
March 11, 2017: [Zhonghua Yan Ke za Zhi] Chinese Journal of Ophthalmology
https://www.readbyqxmd.com/read/28315339/elastic-microfibril-distribution-in-the-cornea-differences-between-normal-and-keratoconic-stroma
#4
Tomas L White, Philip N Lewis, Robert D Young, Koji Kitazawa, Tsutomu Inatomi, Shigeru Kinoshita, Keith M Meek
The optical and biomechanical properties of the cornea are largely governed by the collagen-rich stroma, a layer that represents approximately 90% of the total thickness. Within the stroma, the specific arrangement of superimposed lamellae provides the tissue with tensile strength, whilst the spatial arrangement of individual collagen fibrils within the lamellae confers transparency. In keratoconus, this precise stromal arrangement is lost, resulting in ectasia and visual impairment. In the normal cornea, we previously characterised the three-dimensional arrangement of an elastic fiber network spanning the posterior stroma from limbus-to-limbus...
March 14, 2017: Experimental Eye Research
https://www.readbyqxmd.com/read/28297026/biomechanical-changes-after-in-vivo-collagen-cross-linking-with-rose-bengal-green-light-and-riboflavin-uva
#5
Nandor Bekesi, Patricia Gallego-Muñoz, Lucía Ibarés-Frías, Pablo Perez-Merino, M Carmen Martinez-Garcia, Irene E Kochevar, Susana Marcos
Purpose: To compare corneal biomechanical properties after in vivo and ex vivo cross-linking (CXL) using rose bengal-green light (RGX) or riboflavin-UVA (UVX). Methods: Corneas of 30 rabbits were treated in vivo by the two CXL modalities monolaterally (Group 1) or bilaterally (Group 2). Rabbits in Group 1 were euthanized 1 month after treatments and in Group 2 two months after treatment. Ex vivo CXL was also performed. Eyes were measured by Scheimpflug air puff corneal deformation imaging (Corvis ST) under constant IOP...
March 1, 2017: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/28287858/the-effect-of-pterygium-and-pterygium-surgery-on-corneal-biomechanics
#6
Mustafa Koç, Fuat Yavrum, Mehmet Murat Uzel, Emre Aydemir, Kemal Özülken, Pelin Yılmazbaş
PURPOSE: To evaluate the effect of pterygium and pterygium surgery on corneal biomechanics by ocular response analyzer (ORA, Reichert, USA). METHODS: This study considered 68 eyes (from 34 patients with a mean age of 21.2±7.1 years) with unilateral nasal, primary pterygium (horizontal length <4 mm), and having undergone pterygium excision and conjunctival autografting. Pterygium length and area were measured from a photograph of the anterior segment using Image J program...
March 13, 2017: Seminars in Ophthalmology
https://www.readbyqxmd.com/read/28264134/biomechanical-weakening-of-different-re-treatment-options-after-small-incision-lenticule-extraction-smile
#7
Sabine Kling, Bogdan Spiru, Farhad Hafezi, Walter Sekundo
PURPOSE: To determine the corneal weakening induced by different re-treatment options after small incision lenticule extraction (SMILE) and investigate the potential of corneal cross-linking (CXL) to reestablish the original corneal stress resistance. METHODS: A total of 96 freshly enucleated porcine corneas were used. The initial refractive correction was defined to be -11.00 diopters (D) and the required enhancement to be -3.00 D. Three different re-treatment options were analyzed: -3D Re-SMILE, -3D photorefractive keratectomy (PRK) on top of the SMILE cap, and cap-to-flap conversion and -3D excimer ablation on the stromal bed (LASIK)...
March 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/28260366/-application-value-of-corneal-hysteresis-in-diagnosis-and-treatment-of-glaucoma
#8
L Y He, L Liang, M N Zhu
Glaucoma is the first leading cause of irreversible blindness world widely, but the pathogenesis was still unclear. The collagen fibers from cornea and sclera connect to each other and both of them have similar extracellular matrix components. The biomechanical characteristics of optic nerve lamina cribrosa may associated with the biomechanical properties of the cornea. Therefore, the study of corneal physiological can indirectly reflex the compression and damage in optic nerve lamina cribrosa. The technical developments in corneal hysteresis examination had been updated these years constantly...
February 11, 2017: [Zhonghua Yan Ke za Zhi] Chinese Journal of Ophthalmology
https://www.readbyqxmd.com/read/28255839/impact-of-dehydration-and-fasting-on-intraocular-pressure-and-corneal-biomechanics-measured-by-the-ocular-response-analyzer
#9
Betul Seher Uysal, Necati Duru, Umut Ozen, Mucella Arikan Yorgun, Emine Akcay, Mehtap Caglayan, Nurullah Cagil
PURPOSE: To investigate the effects of dehydration and fasting on the intraocular pressure (IOP) and corneal biomechanics during Ramadan in healthy subjects. METHODS: A total of 36 healthy fasting male volunteers with a mean age of 32.7 ± 5.1 years (range 28-38 years) were enrolled in the study. A Reichert Ocular Response Analyzer (ORA) was used to measure the corneal resistance factor (CRF), corneal hysteresis (CH), Goldman-correlated IOP (IOPg), and corneal-compensated IOP (IOPcc), additionally IOP with Goldmann applanation tonometer (IOP-GAT) was taken...
March 2, 2017: International Ophthalmology
https://www.readbyqxmd.com/read/28251079/corneal-biomechanical-data-and-biometric-parameters-measured-with-scheimpflug-based-devices-on-normal-corneas
#10
Gabor Nemeth, Eszter Szalai, Ziad Hassan, Agnes Lipecz, Zsuzsa Flasko, Laszlo Modis
AIM: To analyze the correlations between ocular biomechanical and biometric data of the eye, measured by Scheimpflug-based devices on healthy subjects. METHODS: Three consecutive measurements were carried out using the corneal visualization Scheimpflug technology (CorVis ST) device on healthy eyes and the 10 device-specific parameters were recorded. Pentacam HR-derived parameters (corneal curvature radii on the anterior and posterior surfaces; apical pachymetry; corneal volume; corneal aberration data; depth, volume and angle of the anterior chamber) and axial length (AL) from IOLMaster were correlated with the 10 specific CorVis ST parameters...
2017: International Journal of Ophthalmology
https://www.readbyqxmd.com/read/28244931/estrogen-and-progesterone-induced-variation-in-corneal-parameters-according-to-hormonal-status
#11
Ayse Ebru Bahadir Kilavuzoglu, Cemile Banu Cosar, Ibrahim Bildirici, Omer Cetin, Esra Ozbasli
OBJECTIVES: To determine the effects of estrogen and progesterone on corneal thickness, curvature, and biomechanics in healthy corneas according to hormonal status. METHODS: The study included four groups of females: group A (menstruating, not pregnant, not lactating, and not menopausal; n=100), group B (pregnant; n=50), group C (lactating; n=50), and group D (menopausal; n=50). Group A was subdivided according to age, as subgroup A15-25 (age 15-25 years) and subgroup A>25 (age >25 years)...
February 27, 2017: Eye & Contact Lens
https://www.readbyqxmd.com/read/28241272/applanation-optical-coherence-elastography-noncontact-measurement-of-intraocular-pressure-corneal-biomechanical-properties-and-corneal-geometry-with-a-single-instrument
#12
Manmohan Singh, Zhaolong Han, Achuth Nair, Alexander Schill, Michael D Twa, Kirill V Larin
No abstract text is available yet for this article.
February 1, 2017: Journal of Biomedical Optics
https://www.readbyqxmd.com/read/28222145/cataract-surgery-causes-biomechanical-alterations-to-the-eye-detectable-by-corvis-st-tonometry
#13
Yoshitake Kato, Shunsuke Nakakura, Ryo Asaoka, Kanae Matsuya, Yuki Fujio, Yoshiaki Kiuchi
PURPOSE: Modern cataract surgery is generally considered to bring about modest and sustained intraocular pressure (IOP) reduction. However, the pathophysiological mechanism for this remains unclear. Moreover, a change in ocular biomechanical properties after surgery can affect the measurement of IOP. The aim of the study is to investigate ocular biomechanics, before and following cataract surgery, using Corvis ST tonometry (CST). PATIENTS AND METHODS: Fifty-nine eyes of 59 patients with cataract were analyzed...
2017: PloS One
https://www.readbyqxmd.com/read/28210179/corneal-biomechanics-in-normal-saudi-individuals
#14
Khalid Al-Arfaj, Sanaa A Yassin, Walaa Al-Dairi, Fatimah Al-Shamlan, Mohanna Al-Jindan
PURPOSE: The aim of this study was to determine and relate corneal biomechanical metrics with demographic, tomographic and refractive data in healthy Saudi people. DESIGN: Prospective, cross-sectional, observational study. PARTICIPANTS: The study included 215 normal Saudi adult individuals. METHODS: Corneal hysteresis (CH) and corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg) and corneal-compensated intraocular pressure (IOPcc) were measured by ocular response analyzer...
July 2016: Saudi Journal of Ophthalmology: Official Journal of the Saudi Ophthalmological Society
https://www.readbyqxmd.com/read/28209504/myopic-surface-ablation-in-asymmetrical-topographies-refractive-results-and-theoretical-corneal-elastic-response
#15
Luis F Brenner, Antonio Renna, Anna Pandolfi, Francisco C Martínez, Jorge L Alió
PURPOSE: To evaluate refractive results and the theoretical elastic response of photorefractive keratectomy in eyes with asymmetrical corneal surface and to compare such outcomes with a control-matched group of normal topographies. DESIGN: Retrospective interventional case series with matched comparison group. METHODS: 30 eyes with superior-inferior dioptric difference (SI index) > 1.40 D, were compared to 30 eyes with normal topographies...
February 13, 2017: American Journal of Ophthalmology
https://www.readbyqxmd.com/read/28192592/an-algorithm-to-predict-the-biomechanical-stiffening-effect-in-corneal-cross-linking
#16
Sabine Kling, Farhad Hafezi
PURPOSE: To develop an algorithm to predict the stiffening effect of CXL and to verify the accuracy with results obtained from experimental measurements. METHODS: The algorithm considers different variables: the reaction kinetics of riboflavin diffusion and riboflavin photodegradation to determine the effective riboflavin concentration in different stromal layers; the oxygen diffusion and ultraviolet (UV) absorption to determine the amount of reactive oxygen species as a function of time and stromal depth...
February 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/28192588/conventional-versus-inverted-side-cut-flaps-for-femtosecond-laser-assisted-lasik-laboratory-and-clinical-evaluation
#17
Vishal Jhanji, Tommy C Y Chan, Wai Ying Li, Rayne R Lim, Marco C Y Yu, Kasin Law, Peng Yi, Yolanda W Y Yip, Yumeng Wang, Tsz Kin Ng, Shyam S Chaurasia, Rajiv R Mohan
PURPOSE: To study the differences in early corneal cellular events and biomechanical properties after femtosecond laser-assisted LASIK performed using conventional or inverted side-cut angles. METHODS: In the laboratory study, left eyes of 24 rabbits underwent LASIK flap creation with a 70° or 115° side-cut. The contralateral eyes served as controls. The corneas were harvested 24 hours postoperatively. In the clinical study, 2 eyes of each patient (n = 29) were randomized to corneal flap creation with 70° or 115° side-cut angles during LASIK...
February 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/28165606/effect-of-topical-antiinflammatory-drugs-on-mechanical-behavior-of-rabbit-cornea
#18
Domenico Lepore, Roberto De Santis, Monica M Pagliara, Antonio Gloria, Olimpia Oliviero, Carlo Nucci, Giovanni Improta, Maria Triassi, Luigi Ambrosio
BACKGROUND: A variety of antiinflammatory therapies are employed to promote corneal wound healing. The effects of steroidal and nonsteroidal antiinflammatory drugs on the biomechanical properties of rabbit cornea were investigated over time using tensile tests. METHODS: Full-thickness incisions were made and used to analyze the effects of dexamethasone sodium phosphate 0.1% and diclofenac sodium 0.1% on corneal biomechanical properties during wound healing at 7, 14 and 21 days after surgery...
February 4, 2017: Journal of Applied Biomaterials & Functional Materials
https://www.readbyqxmd.com/read/28163860/refinement-of-intraocular-pressure-measurements-made-by-ocular-response-analyzer-following-laser-in-situ-keratomileusis-using-m2-90-moria-microkeratome-for-egyptian-myopic-and-astigmatic-patients
#19
Tamer Adel Refai, Olfat A Hassanin
INTRODUCTION: The Goldmann applanation tonometer readings were noted to be markedly reduced after Lasik surgery using a thin flap technique which is widely used nowadays, to correct a wide range of myopia and astigmatism. The Ocular Response Analyzer (ORA) is considered one of the important tools for refinement of Intraocular Pressure (IOP) measurements. The aim of this study is to evaluate and refine ORA measurements for IOP changes post- M2 90 Moria microkeratome Lasik procedure for Egyptian myopic and astigmatic patients trying to aid in glaucoma diagnosis and management...
December 2016: Electronic Physician
https://www.readbyqxmd.com/read/28162196/-comparison-of-the-effects-of-different-side-cut-angles-on-corneal-biomechanical-properties-after-femtosecond-laser-assisted-laser-in-situ-keratomileusis
#20
H Li, Y Wang, R Dou, L Wang, L L Xu, X J Li, J M Zhang
Objective: To evaluate the effects of side-cut angles on corneal biomechanical properties after femtosecond laser assisted-laser in situ keratomileusis (FS-LASIK). Methods: In this clinical control study, 97 right eyes of 97 patients with myopia and myopic astigmatism undergoing FS-LASIK surgery were included randomly. Two types of side-cut angles were designed for the flap, 90° in 48 eyes and 130° in 49 eyes. The values of corneal resistance factor (CRF), cornea hysteresis (CH) and 37 biomechanical waveform parameters were measured using the ocular response analyzer preoperatively and at 1 and 3 months postoperatively...
January 11, 2017: [Zhonghua Yan Ke za Zhi] Chinese Journal of Ophthalmology
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