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Corneal Biomechanics

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https://www.readbyqxmd.com/read/29227513/in-vivo-early-corneal-biomechanical-changes-after-corneal-cross-linking-in-patients-with-progressive-keratoconus
#1
Riccardo Vinciguerra, Vito Romano, Esmaeil M Arbabi, Matthias Brunner, Colin E Willoughby, Mark Batterbury, Stephen B Kaye
PURPOSE: To report early corneal biomechanical changes after corneal cross-linking (CXL) in patients with keratoconus. METHODS: Thirty-four eyes of 34 patients undergoing CXL for progressive keratoconus were included in this prospective clinical study. Dynamic corneal response (DCR) parameters obtained with the Corvis ST (OCULUS Optikgeräte GmbH; Wetzlar, Germany) were assessed at baseline (day of CXL) and after 1 month of follow-up; conversely, corneal tomography with the Pentacam (OCULUS Optikgeräte GmbH) was assessed at baseline and at 1, 3, and 6 months after CXL...
December 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/29200820/the-effect-of-flap-thickness-on-corneal-biomechanics-after-myopic-laser-in-situ-keratomileusis-using-the-m-2-microkeratome
#2
Iyad A Goussous, Mohamed-Sameh El-Agha, Ahmed Awadein, Mohamed H Hosny, Alaa A Ghaith, Ahmed L Khattab
Purpose: The purpose of this study was to determine the effect of flap thickness on corneal biomechanics after myopic laser in situ keratomileusis (LASIK). Methods: This is a prospective controlled non-randomized, institutional study. Patients underwent either epi-LASIK with mitomycin (advanced surface ablation [ASA]), thin-flap LASIK (90 µm head), or thick-flap LASIK (130 µm head). In ASA, the Moria Epi-K hydroseparator was used. LASIK flaps were created using the Moria M-2 mechanical microkeratome...
2017: Clinical Ophthalmology
https://www.readbyqxmd.com/read/29191679/intraocular-pressure-measurements-and-corneal-biomechanical-properties-using-a-dynamic-scheimpflug-analyzer-after-several-keratoplasty-techniques-versus-normal-eyes
#3
J Hugo, E Granget, G Ho Wang Yin, M Sampo, L Hoffart
PURPOSE: To evaluate the biomechanical properties of the cornea and their impact on intraocular pressure (IOP) measurement after lamellar keratoplasty, compared to healthy eyes, using a non-contact tonometer with a Scheimpflug camera. METHODS: This study, from 2014 to 2015, included 22 primary DSAEK, 5 DALK, 6 DSAEK after PK, and 50 control eyes. Using a non-contact tonometer with a high-speed Scheimpflug camera (CORVIS ST, Oculus Optikgeräte GmbH, Wetzlar, Germany), several biomechanical parameters were recorded, including radius at highest concavity (Rhc) and defomation amplitude (DA)...
November 27, 2017: Journal Français D'ophtalmologie
https://www.readbyqxmd.com/read/29178849/goldmann-applanation-tonometry-error-relative-to-true-intracameral-intraocular-pressure-in-vitro-and-in-vivo
#4
Sean McCafferty, Jason Levine, Jim Schwiegerling, Eniko T Enikov
BACKGROUND: Goldmann applanation tonometry (GAT) error relative to intracameral intraocular pressure (IOP) has not been examined comparatively in both human cadaver eyes and in live human eyes. Futhermore, correlations to biomechanical corneal properties and positional changes have not been examined directly to intracameral IOP and GAT IOP. METHODS: Intracameral IOP was measured via pressure transducer on fifty-eight (58) eyes undergoing cataract surgery and the IOP was modulated manometrically on each patient alternately to 10, 20, and 40 mmHg...
November 25, 2017: BMC Ophthalmology
https://www.readbyqxmd.com/read/29176450/corneal-cross-linking-with-verteporfin-and-nonthermal-laser-therapy
#5
Saleh A Alageel, Samer N Arafat, Borja Salvador-Culla, Paraskevi E Kolovou, Khadijeh Jahanseir, Adam Kozak, Gavin J C Braithwaite, Joseph B Ciolino
PURPOSE: To test whether verteporfin with a nonthermal laser increases corneal mechanical stiffness and resistance to enzymatic degradation ex vivo. METHODS: Thirty human corneas (n = 5 per group) were treated with verteporfin alone (V), irradiated with nonthermal laser therapy (689 nm) alone (NTL), or received combined treatment of verteporfin with nonthermal laser therapy for 1 sequence (V+NTL1) or 6 sequences (V+NTL6) of 1 minute of NTL exposure. Positive controls were pretreated with 0...
November 22, 2017: Cornea
https://www.readbyqxmd.com/read/29166180/measurement-of-orbital-biomechanical-properties-in-patients-with-thyroid-orbitopathy-using-the-dynamic-scheimpflug-analyzer-corvis-st
#6
Anna Leszczynska, Karolin Moehler, Eberhard Spoerl, Lisa Ramm, Robert Herber, Lutz E Pillunat, Naim Terai
PURPOSE: To investigate orbital biomechanical properties in patients with thyroid orbitopathy and in age- and gender-matched healthy subjects using the Corvis-ST (CST, Oculus Wetzlar, Germany). METHODS: The CST allows a non-contact tonometry with an ultra-high-speed Scheimpflug device to record the deformation of the cornea during an air pulse. Biomechanical response parameters (intraocular pressure (IOP), whole eye movement length (WEMl) and time (WEMt), deflection amplitude 2 mm ratio max, deflection amplitude max, stiffness parameter, and biomechanically corrected IOP were measured in 39 patients with thyroid orbitopathy (= group I) and in 33 age- and gender-matched healthy subjects (= group II) using the CST...
November 22, 2017: Current Eye Research
https://www.readbyqxmd.com/read/29160595/advanced-anterior-segment-imaging-in-keratoconus-a-review
#7
REVIEW
Akilesh Gokul, Hans R Vellara, Dipika V Patel
Advances in anterior segment imaging have enhanced our ability to detect keratoconus in its early stages and characterise the pathologic changes that occur. Computerised corneal tomography has elucidated the alterations in shape of the anterior and posterior corneal surfaces and alterations in thickness as the disease progresses. Automated screening indices such as the keratoconus screening index were developed to assist in detecting keratoconus in suspicious cases. In vivo assessment of keratoconic corneas has revealed that compromised corneal biomechanics can now be measured clinically...
November 21, 2017: Clinical & Experimental Ophthalmology
https://www.readbyqxmd.com/read/29160542/corneal-biomechanical-features-in-patients-with-ankylosing-spondylitis
#8
Kubra Serefoglu Cabuk, Emine Isil Üstün, Kursat Atalay, Ahmet Kirgiz, Rukiye Aydin
PURPOSE: To evaluate the corneal biomechanical features and central corneal thickness in ankylosing spondylitis patients and to evaluate correlations of these parameters with disease activity. METHODS: The study included 51 patients diagnosed with ankylosing spondylitis (mean age, 40.80 ± 13.15 years; range, 18-72 years) and 34 age- and sex-matched healthy controls (mean age, 42.00 ± 12.32 years; range, 18-60 years). All underwent a complete ophthalmological and physical examination, including visual acuity testing and biomicroscopic anterior and posterior segment examinations...
September 2017: Arquivos Brasileiros de Oftalmologia
https://www.readbyqxmd.com/read/29135719/corneal-biomechanical-properties-in-high-myopia-measured-by-dynamic-scheimpflug-imaging-technology
#9
Miao He, Wei Wang, Hui Ding, Xingwu Zhong
SIGNIFICANCE: The cornea is a viscoelastic tissue with viscous and elastic properties. The information of corneal biomechanical changes in high myopia has implications for understanding the pathogenesis of high myopia and primary open angle glaucoma. However, the knowledge of corneal biomechanics in high myopia is limited. PURPOSE: To compare the corneal biomechanical properties in high-myopia subjects and emmetropia subjects. METHODS: Dynamic Scheimpflug imaging technology was used to measure intraocular pressure, central corneal thickness, and corneal biomechanical parameters, including time at the first applanation, velocity at the first applanation, length at the first applanation, deformation amplitude at the first applanation, time at the second applanation, A2V (velocity at the second applanation), length at the second applanation (A2L), deformation amplitude at the second applanation, time at the highest concavity, radius curvature at the highest concavity (HCR), maximal deformation amplitude (MDA), and peak distance...
December 2017: Optometry and Vision Science: Official Publication of the American Academy of Optometry
https://www.readbyqxmd.com/read/29128531/the-hierarchical-response-of-human-corneal-collagen-to-load
#10
J S Bell, S Hayes, C Whitford, J Sanchez-Weatherby, O Shebanova, C Vergari, C P Winlove, N Terrill, T Sorensen, A Elsheikh, K M Meek
Fibrillar collagen in the human cornea is integral to its function as a transparent lens of precise curvature, and its arrangement is now well-characterised in the literature. While there has been considerable effort to incorporate fibrillar architecture into mechanical models of the cornea, the mechanical response of corneal collagen to small applied loads is not well understood. In this study the fibrillar and molecular response to tensile load was quantified using small and wide angle X-ray scattering (SAXS/WAXS), and digital image correlation (DIC) photography was used to calculate the local strain field that gave rise to the hierarchical changes...
November 8, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/29120713/waveform-analysis-of-deformation-amplitude-and-deflection-amplitude-in%C3%A2-normal-suspect-and-keratoconic-eyes
#11
Mathew Francis, Natasha Pahuja, Rushad Shroff, Roshan Gowda, Himanshu Matalia, Rohit Shetty, Everette J Remington Nelson, Abhijit Sinha Roy
PURPOSE: To evaluate the performance of waveform-derived variables in distinguishing normal, suspect, and keratoconic eyes. SETTING: Narayana Nethralaya Eye Hospital, Bangalore, India. DESIGN: Retrospective case series. METHODS: Scheimpflug tomography (Pentacam) and dynamic Scheimpflug analysis (Corvis ST) of 253 normal (253 patients) eyes and 205 keratoconic eyes (205 patients) were evaluated. Among the 205 patients, 62 had keratoconus in 1 eye, while the unaffected eye was suspect...
October 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/29117418/keratoconus-screening-with-dynamic-biomechanical-in-vivo-scheimpflug-analyses-a-proof-of-concept-study
#12
Johannes Steinberg, Nazanin Eslami Amirabadi, Andreas Frings, Juliane Mehlan, Toam Katz, Stephan J Linke
PURPOSE: This proof-of-concept study was designed to analyze the ability of in vivo biomechanical corneal analyses with the corneal visualization Scheimpflug technology (CorvisST; Oculus Optikgeräte, Wetzlar, Germany) to differentiate between normal eyes and eyes with manifest keratoconus after strictly eliminating the potential confounding factors intraocular pressure (IOP) and central corneal thickness (CCT). METHODS: In this retrospective, cross-sectional study, after pairwise matching for CCT and IOP, 29 normal eyes and 29 keratoconic eyes (one eye from each patient) were selected as study population...
November 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/29116549/transepithelial-accelerated-corneal-collagen-cross-linking-with-higher-oxygen-availability-for-keratoconus-1-year-results
#13
Ling Sun, Meng Li, Xiaoyu Zhang, Mi Tian, Tian Han, Jing Zhao, Xingtao Zhou
PURPOSE: To investigate the safety and efficacy of a new protocol for transepithelial accelerated corneal collagen cross-linking with higher oxygen availability for keratoconus treatment. METHODS: There were 26 patients (26 eyes) diagnosed with keratoconus enrolled in the study and treated with transepithelial accelerated corneal collagen cross-linking. The corneas were irradiated using UVA light for 5 min and 20 s with 45 mW/cm2 irradiance and pulsed illumination (1:1)...
November 7, 2017: International Ophthalmology
https://www.readbyqxmd.com/read/29104870/age-related-variations-of-rabbit-corneal-geometrical-and-clinical-biomechanical-parameters
#14
Haixia Zhang, Xiao Qin, Xiaomeng Cao, Di Zhang, Lin Li
Purpose: To study the variations in corneal clinical biomechanical parameters (CCBP) and corneal geometrical parameters of rabbit in relation to age. Methods: Rabbits aged 3, 7, 12, 18, and 24 months were enrolled. Each eye of the rabbits was tested with Ocular Response Analyzer (ORA), Optical Coherence Tomography (OCT), and Pachymeter to obtain the intraocular pressure (IOP): Goldmann-correlated IOP (IOPg) and Corneal Compensated Intraocular Pressure (IOPcc); CCBP: Corneal Hysteresis (CH) and Corneal Resistance Factor (CRF); corneal geometric parameters: corneal curvature radius (CCR) and central corneal thickness (CCT)...
2017: BioMed Research International
https://www.readbyqxmd.com/read/29101408/corneal-biomechanical-changes-and-tissue-remodeling-after-smile-and-lasik
#15
Rohit Shetty, Mathew Francis, Rushad Shroff, Natasha Pahuja, Pooja Khamar, Molleti Girrish, Rudy M M A Nuijts, Abhijit Sinha Roy
Purpose: To evaluate transient corneal tissue healing and biomechanical changes between laser in situ keratomileusis (LASIK) and small incision lenticule extraction (SMILE) eyes. Methods: In each patient, one eye underwent LASIK and the other underwent SMILE. Optical coherence tomography (OCT) and dynamic Scheimpflug imaging (Corvis-ST) was used to assess tissue healing and biomechanics, respectively. Analyses of OCT scans yielded corneal speckle distribution (CSD) and Bowman's roughness index (BRI)...
November 1, 2017: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/29097675/in-vivo-measurement-of-regional-corneal-tangent-modulus
#16
Ying Hon, Guo-Zhen Chen, Shu-Hao Lu, David Cc Lam, Andrew Kc Lam
Currently available clinical devices are unable to measure corneal biomechanics other than at the central region. Corneal stiffness (S), thickness, and radius of curvature was measured at the central cornea (primary fixation) and 3 mm from the temporal limbus (primary and nasal fixations). The corneal tangent modulus (E) of 25 healthy subjects was calculated from these data. After confirming normality, repeated measures analysis of variance (RMANOVA) revealed significant difference in S (F(2, 48) = 21.36, p < 0...
November 2, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29095506/subacute-effects-of-rose-bengal-green-light-cross-linking-on-rabbit-thin-corneal-stability-and-safety
#17
Ti Wang, Lu Zhu, Jingyin Zhu, Yinbo Peng, Nianci Shen, Yan Yu, Min Yao
BACKGROUND AND PURPOSE: The purpose of this study was to investigate the subacute effects of Rose Bengal (RB) and 532 nm green light-induced photochemical crosslinking (RB-PCL) on rabbit thin corneal stability and safety in vivo. MATERIALS AND METHODS: Rabbit thin corneal models with 250 μm thickness were created by photorefractive keratectomy surgery. Photochemical crosslinking with green light (wavelength 532 nm) at an illumination intensity of 0.4 W/cm(2) for 250 s (100 J/cm(2) ) was performed, followed by antibiotic treatment and slit lamp monitoring for four weeks...
November 2, 2017: Lasers in Surgery and Medicine
https://www.readbyqxmd.com/read/29082447/impact-of-herpetic-stromal-immune-keratitis-in-corneal-biomechanics-and-innervation
#18
Manuel Ángel Marcos-Fernández, Sara Sánchez Tabernero, Jose María Herreras, David José Galarreta
PURPOSE: To study corneal innervation in eyes with history of herpetic keratitis and its correlation with corneal sensitivity and biomechanical properties. METHODS: A total of 56 eyes were included, of which 16 had a history of unilateral immune stromal herpetic keratitis, 16 were their contralateral eyes, and 20 were healthy controls. Structural analysis of corneal nerve plexus was performed by confocal microscopy. Biomechanical properties were measured with the Ocular Response Analyzer...
October 29, 2017: Graefe's Archive for Clinical and Experimental Ophthalmology
https://www.readbyqxmd.com/read/29081866/conventional-versus-accelerated-collagen-cross-linking-for-keratoconus-a-comparison-of-visual-refractive-topographic-and-biomechanical-outcomes
#19
Jyh Haur Woo, Jayant Venkatramani Iyer, Li Lim, M Htoon Hla, Jodhbir S Mehta, Cordelia Ml Chan, Donald Th Tan
OBJECTIVE: The aim was to compare the visual, refractive, topographic and biomechanical outcomes in patients with progressive keratoconus treated with either conventional or accelerated crosslinking at one year follow up. METHODS: It is a prospective, non-randomised interventional study of 76 patients who underwent conventional (CXL; 3mW/cm(2) for 30 minutes) or accelerated cross linking (KXL; 30mW/cm(2) for 4 minutes) for progressive keratoconus. Baseline and postoperative visual acuity, manifest refraction, corneal topography, pachymetry, endothelial cell density and biomechanical parameters of corneal hysteresis and corneal resistance factor were evaluated and compared...
2017: Open Ophthalmology Journal
https://www.readbyqxmd.com/read/29066773/biomechanical-simulation-of-stress-concentration-and-intraocular-pressure-in-corneas-subjected-to-myopic-refractive-surgical-procedures
#20
Po-Jen Shih, I-Jong Wang, Wen-Feng Cai, Jia-Yush Yen
Recent advances in the analysis of corneal biomechanical properties remain difficult to predict the structural stability before and after refractive surgery. In this regard, we applied the finite element method (FEM) to determine the roles of the Bowman's membrane, stroma, and Descemet's membrane in the hoop stresses of cornea, under tension (physiological) and bending (nonphysiological), for patients who undergo radial keratotomy (RK), photorefractive keratectomy (PRK), laser-assisted in situ keratomileusis (LASIK), or small incision lenticule extraction (SMILE)...
October 24, 2017: Scientific Reports
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