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Corneal Biomechanics

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https://www.readbyqxmd.com/read/28644240/corneal-stiffening-by-a-bacteriochlorophyll-derivative-with-dextran-and-near-infrared-light-effect-of-shortening-irradiation-time-up-to-1-minute
#1
Jurriaan Brekelmans, Alexandra Goz, Mor M Dickman, Alexander Brandis, Xiaomeng Sui, H Daniel Wagner, Rudy M M A Nuijts, Avigdor Scherz, Arie L Marcovich
PURPOSE: The aim of this study is to determine the effect of variation of the exposure time of near-infrared irradiation on corneal stiffening after a bacteriochlorophyll derivative (WST11) with dextran (WST-D) application. METHODS: One hundred four paired eyes of 3-month-old New Zealand White rabbits were included in this study. Fifty-two eyes (ex vivo n = 34, in vivo n = 18) were mechanically deepithelialized, treated topically with WST-D, and irradiated at 10 mW/cm using a diode laser at 755 nm for 1, 5, or 30 minutes...
June 21, 2017: Cornea
https://www.readbyqxmd.com/read/28636261/characteristics-of-corneal-biomechanical-responses-detected-by-a-non-contact-scheimpflug-based-tonometer-in-eyes-with-glaucoma
#2
Younhea Jung, Hae-Young L Park, Hee Jung Yang, Chan Kee Park
PURPOSE: To determine the corneal biomechanical properties in eyes with glaucoma using a non-contact Scheimpflug-based tonometer. METHODS: Corneal biomechanical responses were examined using a non-contact Scheimpflug-based tonometer. The tonometer parameters of the normal control group (n = 75) were compared with those of the glaucoma group (n = 136), including an analysis of glaucoma subgroups categorized by visual field loss. RESULTS: After adjusting for potential confounding factors, including the intraocular pressure (IOP), central corneal thickness (CCT), age and axial length, the deformation amplitude was smaller in the glaucoma group (1...
June 21, 2017: Acta Ophthalmologica
https://www.readbyqxmd.com/read/28626817/comparison-of-current-tonometry-techniques-in-measurement-of-intraocular-pressure
#3
Behrooz Kouchaki, Hassan Hashemi, Abbasali Yekta, Mehdi Khabazkhoob
PURPOSE: To compare four tonometry techniques: Goldmann applanation tonometer (GAT), Dynamic contour tonometer (DCT), Non-contact tonometer (NCT), and Ocular Response Analyzer (ORA) in the measurement of intraocular pressure (IOP) and the impact of some corneal biomechanical factors on their performance. METHODS: In this cross-sectional study, volunteers with normal ophthalmic examination and no history of eye surgery (except for uncomplicated cataract surgery) or trauma were selected...
June 2017: Journal of Current Ophthalmology
https://www.readbyqxmd.com/read/28626602/association-between-corneal-biomechanical-properties-with-ocular-response-analyzer-and-also-corvisst-tonometry-and-glaucomatous-visual-field-severity
#4
Kazunori Hirasawa, Masato Matsuura, Hiroshi Murata, Shunsuke Nakakura, Yoshitaka Nakao, Yoshiaki Kiuchi, Ryo Asaoka
PURPOSE: To investigate the association between corneal biomechanical properties measured with the Ocular Response Analyzer (ORA) and also CorvisST (CST) tonometry, and glaucomatous visual field (VF) severity. METHODS: One hundred forty-six eyes of 91 patients with primary open-angle glaucoma who performed Humphrey Field Analyzer 30-2 or 24-2 SITA-Standard, ORA, and CST within 180 days were included in this multicentral, observational cross-sectional study. The association between ORA parameters (corneal hysteresis [CH] and corneal resistant factor [CRF]), CST parameters (A1 and A2 time, A1 and A2 length, A1 and A2 velocity, A1 and A2 deformation amplitude, highest deformation amplitude, highest concavity time, peak distance, and radius), and other basic parameters (age, intraocular pressure with Goldmann applanation tonometry, central corneal thickness, and axial length) against mean total deviation (mTD) were analyzed using a linear mixed-model and model selection with corrected Akaike Information Criterion (AICc)...
June 2017: Translational Vision Science & Technology
https://www.readbyqxmd.com/read/28603017/effects-of-diabetes-mellitus-on-biomechanical-properties-of-the-rabbit-cornea
#5
FangJun Bao, ManLi Deng, XiaoBo Zheng, LinNa Li, YiPing Zhao, Si Cao, AYong Yu, QinMei Wang, JinHai Huang, Ahmed Elsheikh
To investigate the effects of diabetes on the biomechanical behavior of cornea in alloxan-induced diabetic rabbits. Diabetes mellitus (DM) was induced in 20 rabbits using alloxan, while another 20 age- and weight-matched non-diabetic rabbits served as controls. Eyes were enucleated after 8 weeks of inducing diabetes and the whole cornea was removed with a 3 mm wide scleral ring and tested under inflation conditions with an internal pressure range of 2.0-30.0 mmHg to determine their stress-strain behavior using an inverse analysis process...
June 8, 2017: Experimental Eye Research
https://www.readbyqxmd.com/read/28590790/the-effect-of-ascorbic-acid-vitamin-c-on-transepithelial-corneal-cross-linking-in-rabbits
#6
Mustafa Koc, Basak Bostanci, Ozlem Ozbas Demirel, Feyza Genc, Kemal Tekin, Yaran Koban, Aylin Sepici Dincel, Murat Sen, Pelin Yilmazbas
PURPOSE: To evaluate the effects of ascorbic acid (vitamin C), the main antioxidant agent in the cornea on transepithelial corneal cross-linking (CXL) where the main mechanism is oxidation. METHODS: Twenty eyes of 20 rabbits were divided into 3 groups: Group 1 (7 eyes) had transepithelial corneal CXL after being fed with normal diet; Group 2 (7 eyes) had corneal CXL after once-daily subcutaneous injections of 200 mg of ascorbic acid in addition to normal diet; and the control group (6 eyes) was fed with normal diet but did not have corneal CXL performed...
June 7, 2017: Journal of Ocular Pharmacology and Therapeutics
https://www.readbyqxmd.com/read/28586502/biomechanical-changes-after-lasik-flap-creation-combined-with-rapid-cross-linking-measured-with-brillouin-microscopy
#7
J Bradley Randleman, Johnny P Su, Giuliano Scarcelli
PURPOSE: To evaluate the biomechanical changes occurring after LASIK flap creation and rapid corneal cross-linking (CXL) measured with Brillouin light microscopy. METHODS: Porcine eyes (n = 11) were evaluated by Brillouin light microscopy sequentially in the following order: virgin state, after LASIK flap creation, and after rapid CXL. Each eye served as its own control. Depth profile of the Brillouin frequency shift was computed to reveal the depth-dependent changes in corneal stiffness...
June 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/28579539/preparation-of-acellular-scaffold-for-corneal-tissue-engineering-by-supercritical-carbon-dioxide-extraction-technology
#8
Yi-Hsun Huang, Fan-Wei Tseng, Wen-Hsin Chang, I-Chen Peng, Dar-Jen Hsieh, Shu-Wei Wu, Ming-Long Yeh
In this study, we developed a novel method using supercritical carbon dioxide (SCCO2) to prepare acellular porcine cornea (APC). Under gentle extraction conditions using SCCO2 technology, hematoxylin and eosin staining showed that cells were completely lysed, and cell debris, including nuclei, was efficiently removed from the porcine cornea. The SCCO2-treated corneas exhibited intact stromal structures and appropriate mechanical properties. Moreover, no immunological reactions and neovascularization were observed after lamellar keratoplasty in rabbits...
June 1, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28559158/tissue-and-cellular-biomechanics-during-corneal-wound-injury-and-repair
#9
Vijay Krishna Raghunathan, Sara M Thomasy, Peter Strøm, Bernardo Yañez-Soto, Shaun P Garland, Jasmyne Sermeno, Christopher M Reilly, Christopher J Murphy
Corneal wound healing is an enormously complex process that requires the simultaneous cellular integration of multiple soluble biochemical cues, as well as cellular responses to the intrinsic chemistry and biophysical attributes associated with the matrix of the wound space. Here, we document how the biomechanics of the corneal stroma are altered through the course of wound repair following keratoablative procedures in rabbits. Further we documented the influence that substrate stiffness has on stromal cell mechanics...
May 27, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28546925/comparison-of-corneal-biomechanics-in-sj%C3%A3-gren-s-syndrome-and-non-sj%C3%A3-gren-s-syndrome-dry-eyes-by-scheimpflug-based-device
#10
Qin Long, Jing-Yi Wang, Dong Xu, Ying Li
AIM: To compare the corneal biomechanics of Sjögren's syndrome (SS) and non-SS dry eyes with Corneal Visualization Scheimpflug Technology (CorVis ST). METHODS: Corneal biomechanics and tear film parameters, namely the Schirmer I test value, tear film break-up time (TBUT) and corneal staining score (CSS) were detected in 34 eyes of 34 dry eye patients with SS (SSDE group) and 34 dry eye subjects without SS (NSSDE group) using CorVis ST. The differences of the above parameters between the two groups were examined, and the relationship between corneal biomechanics and tear film parameters were observed...
2017: International Journal of Ophthalmology
https://www.readbyqxmd.com/read/28540578/-complications-and-postoperative-therapeutic-strategies-in-cross-linking
#11
REVIEW
M Kohlhaas
CLINICAL ISSUE: The reduced corneal mechanical stability in keratoconus and similar collagen diseases can lead to a progressive and irregular corneal shape and decrease of visual acuity. DIAGNOSTICS: A progression of keratectatic diseases can be shown with corneal topography. TREATMENT: Keratoconus can be treated by photo-oxidative cross-linking of the corneal collagen. In order to achieve a high absorption of irradiation energy in the cornea, riboflavin at a concentration of 0...
May 24, 2017: Der Ophthalmologe: Zeitschrift der Deutschen Ophthalmologischen Gesellschaft
https://www.readbyqxmd.com/read/28540493/investigation-of-corneal-biomechanics-at-moderate-to-high-refractive-errors
#12
Nehir İnceoğlu, Sinan Emre, Mahmut Oğuz Ulusoy
PURPOSE: Corneal hysteresis (CH) and corneal resistance factor (CRF) are corneal biomechanical parameters which were measured by ocular response analyzer (ORA). Aim of this study was to define the CH and CRF in high myopic and hyperopic patients and compare the results with emmetropic control group. METHODS: A total of 193 eyes of 100 healthy volunteers were included. Study groups were high myopic patients (n = 27) with spherical refractive errors (SRE) of greater than -5...
May 24, 2017: International Ophthalmology
https://www.readbyqxmd.com/read/28538668/biomechanical-modeling-of-pterygium-radiation-surgery-a-retrospective-case-study
#13
Bojan Pajic, Daniel M Aebersold, Andreas Eggspuehler, Frederik R Theler, Harald P Studer
Pterygium is a vascularized, invasive transformation on the anterior corneal surface that can be treated by Strontium-/Yttrium90 beta irradiation. Finite element modeling was used to analyze the biomechanical effects governing the treatment, and to help understand clinically observed changes in corneal astigmatism. Results suggested that irradiation-induced pulling forces on the anterior corneal surface can cause astigmatism, as well as central corneal flattening. Finite element modeling of corneal biomechanics closely predicted the postoperative corneal surface (astigmatism error -0...
May 24, 2017: Sensors
https://www.readbyqxmd.com/read/28514942/corneal-biomechanical-properties-in-healthy-children-measured-by-corneal-visualization-scheimpflug-technology
#14
Miao He, Hui Ding, Hong He, Chi Zhang, Liangping Liu, Xingwu Zhong
BACKGROUND: The aim of this study was to evaluate corneal biomechanical properties in a population of healthy children in China using corneal visualization Scheimpflug technology (CST). METHODS: All children underwent complete bi-ocular examinations. CST provided intraocular pressure (IOP) and corneal biomechanical parameters, including time, velocity, length and deformation amplitude at first applanation (A1T, A1V, A1L, A1DA), at second applanation (A2T, A2V, A2L, A2DA), highest concavity time (HCT), maximum deformation amplitude (MDA), peak distance (PD), and radius of curvature (RoC)...
May 17, 2017: BMC Ophthalmology
https://www.readbyqxmd.com/read/28501948/corneal-tomography-and-biomechanics-in-primary-pterygium
#15
M Vanathi, Sahil Goel, Anita Ganger, Tushar Agarwal, T Dada, Sudarshan Khokhar
PURPOSE: To study the Scheimpflug's imaging and corneal biomechanics in primary pterygium. METHODS: A prospective observational study of 55 patients with unilateral primary nasal pterygium was done. The normal fellow eyes of patients with pterygium were taken as controls. Clinical parameters noted included visual acuity, values of corneal curvature by doing Scheimpflug imaging, wavefront aberrations in terms of higher and lower-order aberrations and corneal hysteresis (CH) as well as corneal resistance factor (CRF) values by using ocular response analyzer...
May 13, 2017: International Ophthalmology
https://www.readbyqxmd.com/read/28496302/goldmann-tonometer-error-correcting-prism-clinical-evaluation
#16
Sean McCafferty, Garrett Lim, William Duncan, Eniko T Enikov, Jim Schwiegerling, Jason Levine, Corin Kew
PURPOSE: Clinically evaluate a modified applanating surface Goldmann tonometer prism designed to substantially negate errors due to patient variability in biomechanics. METHODS: A modified Goldmann prism with a correcting applanation tonometry surface (CATS) was mathematically optimized to minimize the intraocular pressure (IOP) measurement error due to patient variability in corneal thickness, stiffness, curvature, and tear film adhesion force. A comparative clinical study of 109 eyes measured IOP with CATS and Goldmann prisms...
2017: Clinical Ophthalmology
https://www.readbyqxmd.com/read/28494490/biomechanical-responses-of-lamina-cribrosa-to-intraocular-pressure-change-assessed-by-optical-coherence-tomography-in-glaucoma-eyes
#17
Harry Quigley, Karun Arora, Sana Idrees, Francisco Solano, Sahar Bedrood, Christopher Lee, Joan Jefferys, Thao Nguyen
Purpose: The purpose of this study was to measure change in anterior lamina cribrosa depth (ALD) globally and regionally in glaucoma eyes at different intraocular pressures (IOP). Methods: Twenty-seven glaucoma patients were imaged before and after IOP-lowering procedures using optical coherence tomography. The anterior lamina was marked in approximately 25 locations in each of six radial scans to obtain global and regional estimates of ALD. ALD and its change with IOP were compared with optic disc damage, nerve fiber layer thickness, and visual field loss...
May 1, 2017: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/28489806/the-relationship-between-corneal-biomechanics-and-anterior-segment-parameters-in-the-early-stage-of-orthokeratology-a-pilot-study
#18
Renai Chen, Xinjie Mao, Jun Jiang, Meixiao Shen, Yan Lian, Bin Zhang, Fan Lu
To investigate the relationship between corneal biomechanics and anterior segment parameters in the early stage of overnight orthokeratology.Twenty-three eyes from 23 subjects were involved in the study. Corneal biomechanics, including corneal hysteresis (CH) and corneal resistance factor (CRF), and parameters of the anterior segment, including corneal curvature, central corneal thickness (CCT), and corneal sublayers' thickness, were measured at baseline and day 1 and 7 after wearing orthokeratology lens. One-way analysis of variance with repeated measures was used to compare the longitudinal changes and partial least squares linear regression was used to explore the relationship between corneal biomechanics and anterior segment parameters...
May 2017: Medicine (Baltimore)
https://www.readbyqxmd.com/read/28486312/biomechanical-and-histopathologic-effects-of-pulsed-light-accelerated-epithelium-on-off-corneal-collagen-cross-linking
#19
Xiaoyu Zhang, Ling Sun, Yang Shen, Mi Tian, Jing Zhao, Yu Zhao, Meiyan Li, Xingtao Zhou
PURPOSE: This study aimed to compare the biomechanical and histopathologic effects of transepithelial and accelerated epithelium-off pulsed-light accelerated corneal collagen cross-linking (CXL). METHODS: A total of 24 New Zealand rabbits were analyzed after sham operation (control) or transepithelial or epithelium-off operation (45 mW/cm for both). The transepithelial group was treated with pulsed-light ultraviolet A for 5 minutes 20 seconds, and the epithelium-off group was treated for 90 seconds...
July 2017: Cornea
https://www.readbyqxmd.com/read/28472178/influence-of-eye-biometrics-and-corneal-micro-structure-on-noncontact-tonometry
#20
Danilo A Jesus, Małgorzata Majewska, Patrycja Krzyżanowska-Berkowska, D Robert Iskander
PURPOSE: Tonometry is widely used as the main screening tool supporting glaucoma diagnosis. Still, its accuracy could be improved if full knowledge about the variation of the corneal biomechanical properties was available. In this study, Optical Coherence Tomography (OCT) speckle statistics are used to infer the organisation of the corneal micro-structure and hence, to analyse its influence on intraocular pressure (IOP) measurements. METHODS: Fifty-six subjects were recruited for this prospective study...
2017: PloS One
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