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Corneal Biomechanics

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https://www.readbyqxmd.com/read/28222145/cataract-surgery-causes-biomechanical-alterations-to-the-eye-detectable-by-corvis-st-tonometry
#1
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
#2
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
#3
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
#4
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
#5
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
#6
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
#7
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
#8
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
https://www.readbyqxmd.com/read/28162194/-analysis-on-corneal-deformation-and-corneal-biomechanical-changes-after-small-incision-lenticule-extraction
#9
Y L Huang, Y Wang, R Dou, S B Jin, L J Liu, H Li, P H Wei
Objective: To investigate biomechanical effects of central corneal thickness (CCT), and to explore the possible safe range for the tissue removal and percentage of tissue ablation (PTA) of small incision lenticule extraction (SMILE). Methods: Clinical observational study. One hundred and eighty-seven cases (365 eyes) undergoing SMILE surgery were enrolled. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured before and after surgery by the ocular response analyzer (ORA). Linear regression of CH, CRF and CCT, and percentage of tissue ablation were calculated...
January 11, 2017: [Zhonghua Yan Ke za Zhi] Chinese Journal of Ophthalmology
https://www.readbyqxmd.com/read/28151939/role-of-percent-peripheral-tissue-ablated-on-refractive-outcomes-following-hyperopic-lasik
#10
George Fatseas, Fiona Stapleton, Patrick Versace
OBJECTIVES: To determine the effect of hyperopic laser in situ keratomileusis (H-LASIK) on corneal integrity, by investigating relationships between proportionate corneal tissue ablated and refractive outcomes at 3 months. METHODS: 18 eyes of 18 subjects treated with H-LASIK by Technolas 217c Excimer Laser were included in the study. Orbscan II Topography System was used to determine corneal volume and pachymetry 3mm temporally (3T). The volume of corneal tissue ablated was determined from the laser nomogram...
2017: PloS One
https://www.readbyqxmd.com/read/28149787/small-incision-lenticule-extraction-versus-femtosecond-lenticule-extraction-for-myopic-a-systematic-review-and-meta-analysis
#11
Jia-Song Wang, Hua-Tao Xie, Ye Jia, Ming-Chang Zhang
AIM: To examine differences in efficacy, accuracy, safety, aberrations and corneal biomechanical between Small incision lenticule extraction (SMILE) and femtosecond lenticule extraction (FLEx) for myopia. METHODS: Comprehensive studies were conducted on the PubMed, MEDLINE, EMBASE, and Cochrane Controlled Trials Register before 31 July, 2015. Meta-analyses were performed on the primary outcomes [loss of ≥2 lines of corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA) ≥20/20, spherical equivalent (SE) within ±0...
2017: International Journal of Ophthalmology
https://www.readbyqxmd.com/read/28139518/corneal-biomechanical-parameters-and-asymmetric-visual-field-damage-in-patients-with-untreated-normal-tension-glaucoma
#12
Bai-Bing Li, Yu Cai, Ying-Zi Pan, Mei Li, Rong-Hua Qiao, Yuan Fang, Tian Tian
BACKGROUND: High intraocular pressure (IOP) and low central corneal thickness (CCT) are important validated risk factors for glaucoma, and some studies also have suggested that eyes with more deformable corneas may be in higher risk of the development and worsening of glaucoma. In the present study, we aimed to evaluate the association between corneal biomechanical parameters and asymmetric visual field (VF) damage using a Corvis-ST device in patients with untreated normal tension glaucoma (NTG)...
2017: Chinese Medical Journal
https://www.readbyqxmd.com/read/28139064/corneal-profile-in-primary-congenital-glaucoma
#13
Azadeh Doozandeh, Shahin Yazdani, Shabnam Ansari, Mohammad Pakravan, Tahmineh Motevasseli, Bagher Hosseini, Mehdi Yasseri
PURPOSE: To investigate biomechanical and ultrastructural corneal parameters and ocular biometrics in the affected eyes of patients with unilateral primary congenital glaucoma (PCG) as compared to unaffected fellow eyes and age-matched healthy controls. METHODS: A total of 12 patients with treated unilateral PCG and 10 normal subjects were evaluated. LENSTAR was performed to determine biometric parameters; the ocular response analyser was employed to determine biomechanical properties and slit-scanning confocal microscopy was used for evaluation of corneal ultrastucture...
January 31, 2017: Acta Ophthalmologica
https://www.readbyqxmd.com/read/28129421/factors-associated-with-corneal-deformation-responses-measured-with-a-dynamic-scheimpflug-analyzer
#14
Atsuya Miki, Naoyuki Maeda, Yasushi Ikuno, Tomoko Asai, Chikako Hara, Kohji Nishida
Purpose: The purpose of this study was to clarify correlations between corneal deformation parameters measured with a dynamic Scheimpflug analyzer and baseline factors such as axial length, intraocular pressure (IOP), age, central corneal thickness (CCT), and corneal curvature. Methods: Ninety-six eyes of 96 healthy subjects (mean 55.2 ± 16.1 years of age) were examined using a dynamic Scheimpflug analyzer. Eighteen of 35 deformation parameters were selected for analyses based on measurement reliability and clinical relevance...
January 1, 2017: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/28125860/corneal-biomechanics-a-review
#15
REVIEW
Sabine Kling, Farhad Hafezi
PURPOSE: In recent years, the interest in corneal biomechanics has strongly increased. The material properties of the cornea determine its shape and therefore play an important role in corneal ectasia and related pathologies. This review addresses the molecular origin of biomechanical properties, models for their description, methods for their characterisation, techniques for their modification, and computational simulation approaches. RECENT FINDINGS: Recent research has focused on developing non-contact techniques to measure the biomechanical properties in vivo, on determining structural and molecular abnormalities in pathological corneas, on developing and optimising techniques to reinforce the corneal tissue and on the computational simulation of surgical interventions...
January 26, 2017: Ophthalmic & Physiological Optics: the Journal of the British College of Ophthalmic Opticians (Optometrists)
https://www.readbyqxmd.com/read/28114577/biomechanical-strengthening-of-the-human-cornea-induced-by-nanoplatform-based-transepithelial-riboflavin-uv-a-corneal-cross-linking
#16
Cristina Labate, Marco Lombardo, Giuseppe Lombardo, Maria Penelope De Santo
Purpose: The purpose of this study was to investigate the biomechanical stiffening effect induced by nanoplatform-based transepithelial riboflavin/UV-A cross-linking protocol using atomic force microscopy (AFM). Methods: Twelve eye bank donor human sclerocorneal tissues were investigated using a commercial atomic force microscope operated in force spectroscopy mode. Four specimens underwent transepithelial corneal cross-linking using a hypotonic solution of 0.1% riboflavin with biodegradable polymeric nanoparticles of 2-hydroxypropyl-β-cyclodextrin plus enhancers (trometamol and ethylenediaminetetraacetic acid) and UV-A irradiation with a 10 mW/cm2 device for 9 minutes...
January 1, 2017: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/28101423/assessing-the-effects-of-riboflavin-uv-a-crosslinking-on-porcine-corneal-mechanical-anisotropy-with-optical-coherence-elastography
#17
Manmohan Singh, Jiasong Li, Zhaolong Han, Raksha Raghunathan, Achuth Nair, Chen Wu, Chih-Hao Liu, Salavat Aglyamov, Michael D Twa, Kirill V Larin
In this work we utilize optical coherence elastography (OCE) to assess the effects of UV-A/riboflavin corneal collagen crosslinking (CXL) on the mechanical anisotropy of in situ porcine corneas at various intraocular pressures (IOP). There was a distinct meridian of increased Young's modulus in all samples, and the mechanical anisotropy increased as a function of IOP and also after CXL. The presented noncontact OCE technique was able to quantify the Young's modulus and elastic anisotropy of the cornea and their changes as a function of IOP and CXL, opening new avenues of research for evaluating the effects of CXL on corneal biomechanical properties...
January 1, 2017: Biomedical Optics Express
https://www.readbyqxmd.com/read/28101409/assessment-of-corneal-properties-based-on-statistical-modeling-of-oct-speckle
#18
Danilo A Jesus, D Robert Iskander
A new approach to assess the properties of the corneal micro-structure in vivo based on the statistical modeling of speckle obtained from Optical Coherence Tomography (OCT) is presented. A number of statistical models were proposed to fit the corneal speckle data obtained from OCT raw image. Short-term changes in corneal properties were studied by inducing corneal swelling whereas age-related changes were observed analyzing data of sixty-five subjects aged between twenty-four and seventy-three years. Generalized Gamma distribution has shown to be the best model, in terms of the Akaike's Information Criterion, to fit the OCT corneal speckle...
January 1, 2017: Biomedical Optics Express
https://www.readbyqxmd.com/read/28095867/effects-of-ablation-depth-and-repair-time-on-the-corneal-elastic-modulus-after-laser-in-situ-keratomileusis
#19
Xiaojun Wang, Xiaona Li, Weiyi Chen, Rui He, Zhipeng Gao, Pengfei Feng
BACKGROUND: The biomechanical properties of the cornea should be taken into account in the refractive procedure in order to perform refractive surgery more accurately. The effects of the ablation depth and repair time on the elastic modulus of the rabbit cornea after laser in situ keratomileusis (LASIK) are still unclear. METHODS: In this study, LASIK was performed on New Zealand rabbits with different ablation depth (only typical LASIK flaps were created; residual stroma bed was 50 or 30% of the whole cornea thickness respectively)...
January 17, 2017: Biomedical Engineering Online
https://www.readbyqxmd.com/read/28081172/influence-of-corneal-opacity-on-intraocular-pressure-assessment-in-patients-with-lysosomal-storage-diseases
#20
Joanna Wasielica-Poslednik, Giuseppe Politino, Irene Schmidtmann, Katrin Lorenz, Katharina Bell, Norbert Pfeiffer, Susanne Pitz
AIMS: To investigate an influence of mucopolysaccharidosis (MPS)- and Morbus Fabry-associated corneal opacities on intraocular pressure (IOP) measurements and to evaluate the concordance of the different tonometry methods. METHODS: 25 MPS patients with or without corneal clouding, 25 Fabry patients with cornea verticillata ≥ grade 2 and 25 healthy age matched controls were prospectively included into this study. Outcome measures: Goldmann applanation tonometry (GAT); palpatory assessment of IOP; Goldmann-correlated intraocular pressure (IOPg), corneal-compensated intraocular pressure (IOPcc), corneal resistance factor (CRF) and corneal hysteresis (CH) assessed by Ocular Response Analyzer (ORA); central corneal thickness (CCT) and density assessed with Pentacam...
2017: PloS One
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