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Corneal Biomechanics

Ashkan Eliasy, Kai-Jung Chen, Riccardo Vinciguerra, Osama Maklad, Paolo Vinciguerra, Renato Ambrósio, Cynthia J Roberts, Ahmed Elsheikh
The purpose of this study was to assess the validity of the Corvis ST (Oculus; Wetzlar, Germany) biomechanical correction algorithm (bIOP) in determining intraocular pressure (IOP) using experiments on ex-vivo human eyes. Five ex-vivo human ocular globes (age 69 ± 3 years) were obtained and tested within 3-5 days post mortem. Using a custom-built inflation rig, the internal pressure of the eyes was controlled mechanically and measured using the CorVis ST (CVS-IOP). The CVS-IOP measurements were then corrected to produce bIOP, which was developed for being less affected by variations in corneal biomechanical parameters, including tissue thickness and material properties...
June 14, 2018: Experimental Eye Research
Yaoqi Xiang, Min Shen, Chao Xue, Di Wu, Yan Wang
The biomechanical behavior of human corneal stroma under uniaxial tension was investigated by the experimental analysis of cornea stromal lenticules taken out by corneal refractive surgery. Uniaxial tests were conducted to determine their stress-strain relationship and tensile strength. The Gasser-Ogden-Holzapfel (GOH) model was used to describe biomechanical behavior of the corneal stroma. The theoretical stress-strain relationship of the GOH model in the uniaxial tensile test was deduced. The corneal specimens were collected from ten patients (4 male and 6 female), aged from 17 to 36...
May 30, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Sepehr Feizi, Amir Faramarzi, Ali Masoudi, Amir A Azari, Amirreza Veisi
PURPOSE: To evaluate agreement between IOP measured using the ocular response analyzer (ORA) versus using the Goldmann applanation tonometer (GAT) in patients treated by Descemet stripping automated endothelial keratoplasty (DSAEK). METHODS: This prospective, case-control study comprised 38 normal eyes and 37 post-DSAEK eyes. IOP was measured using the GAT (IOPGAT). The ORA was used to measure corneal biomechanics and cornea-compensated IOP (IOPCC). Corneal hysteresis (CH), corneal resistance factor, and IOP measurements of the 2 groups were compared...
June 5, 2018: Cornea
Thomas A Fuchsluger, Susanne Brettl, Gerd Geerling, Wolfgang Kaisers, Philipp Franko Zeitz
AIMS: To examine corneal biomechanics in healthy and keratoconic eyes, with or without crosslinking obtained by ultrahigh-speed Scheimpflug measurements (Corvis ST). METHODS: One hundred and seventeen eyes were studied in three groups: group 1 (n=39) contained keratoconic eyes without crosslinking. Group 2 (CXL; n=28) comprised keratoconic eyes after crosslinking. These were compared with a control group (n=50 matched healthy eyes). In addition, 10 keratoconus patients, before and after CXL treatment, respectively, were examined...
June 5, 2018: British Journal of Ophthalmology
Mohamed S Sayed, Richard K Lee
No abstract text is available yet for this article.
2018: International Ophthalmology Clinics
Mohammad-Reza Sedaghat, Hamed Momeni-Moghaddam, Renato Ambrósio, Hamid-Reza Heidari, Nasim Maddah, Zeynab Danesh, Fatemeh Sabzi
PURPOSE: To assess the diagnostic capability of corneal shape and biomechanical parameters for distinguishing normal eyes from frank keratoconus (KCN). METHODS: This is a retrospective analysis of eyes of 137 control subjects and 145 patients with KCN, with one of their eyes randomly selected as the study eye. Corneal biomechanical parameters were assessed using the Corvis ST (Oculus Optikgeräte GmbH) and Oculus Response Analyzer (Reichert Ophthalmic Instruments)...
May 25, 2018: Cornea
Mohamed Nagy Elmohamady, Walid Abdelghaffar, Ahmed Daifalla, Tamer Salem
Purpose: To evaluate femtosecond laser in flap and cap creation, detect some corneal biomechanical changes, and evaluate dry eye after laser in situ keratomileusis (LASIK), Femto-LASIK, and small incision lenticule extraction (SMILE) with 3-year follow-up. Patients and methods: Preoperative evaluation taken: full ophthalmic examination, Pentacam, ocular response analyzer, ocular surface disease index (OSDI), and tear breakup time (TBUT). LASIK flap was created using Moria microkeratome in 30 eyes (LASIK group) and using VisuMax femtosecond laser in 38 eyes (FS-LASIK group) and SMILE was done by VisuMax in 35 eyes (SMILE group)...
2018: Clinical Ophthalmology
Shotaro Asano, Kosuke Nakajima, Kana Kure, Keiko Azuma, Kimiko Shimizu, Hiroshi Murata, Tatsuya Inoue, Ryo Obata, Ryo Asaoka
The aim of the current study is to investigate corneal biomechanical properties in detail using Ocular Response Analyzer (ORA) and Corvis ST (CST) tonometry and to analyze the association between corneal biomechanical properties and the frequency of intravitreal anti-vascular endothelial growth factor (VEGF) injections (FIV ) in AS eyes with choroidal neovascularization (CNV). Twenty-eight eyes of 15 patients with AS were enrolled. Mean age of AS patients was 67.9 ± 9.8 years. ORA and CST measurements were carried out, in addition to comprehensive ophthalmic examinations...
May 25, 2018: Scientific Reports
Bruno Zappone, Navinkumar J Patil, Marco Lombardo, Giuseppe Lombardo
Knowledge of the biomechanical properties of the human cornea is crucial for understanding the development of corneal diseases and impact of surgical treatments (e.g., corneal laser surgery, corneal cross-linking). Using a Surface Force Apparatus we investigated the transient viscous response of the anterior cornea from donor human eyes compressed between macroscopic crossed cylinders. Corneal biomechanics was analyzed using linear viscoelastic theory and interpreted in the framework of a biphasic model of soft hydrated porous tissues, including a significant contribution from the pressurization and viscous flow of fluid within the corneal tissue...
2018: PloS One
Laura Morales-Fernandez, Javier Garcia-Bella, Jose M Martinez-de-la-Casa, Rubén Sanchez-Jean, Federico Saenz-Frances, Pedro Arriola-Villalobos, Lucia Perucho, Enrique Santos-Bueso, Julian Garcia-Feijoo
OBJECTIVE: This study was designed to assess changes in corneal topography and biomechanics after intraocular pressure (IOP) monitoring using the Triggerfish contact lens sensor (CLS). METHODS: For this prospective study, 30 eyes of 30 subjects: 14 healthy subjects (G1) and 6 glaucoma patients (G2), were recruited for 24 hours of continuous IOP monitoring using the CLS. The following measurements were taken before CLS fitting and after lens removal: maximum keratometry (Kmax), mean keratometry (MK), and corneal astigmatism (Cyl) measured through Pentacam corneal topography, and the corneal biomechanical variables corneal hysteresis (CH) and corneal resistance factor (CRF) measured with the Ocular Response Analyzer (ORA)...
June 2018: Canadian Journal of Ophthalmology. Journal Canadien D'ophtalmologie
Ronald R Krueger, Caio S Meister
PURPOSE OF REVIEW: As a flapless procedure, SMILE brings benefits to refractive surgery, such as lower corneal biomechanical impact, less dry eye risk and less stromal bed exposure. However, the longer learning curve can be a risk factor for complications. This article aims to discuss SMILE complications and proposes a categorized analysis of occurrences, dividing into two groups: intraoperative and postoperative complications. Among intraoperative, we also suggest a subdivision between those related to the laser (lenticule construction), tissue separation (lenticule dissection) and tissue removal (lenticule extraction)...
July 2018: Current Opinion in Ophthalmology
Vinicius S De Stefano, Ibrahim Seven, J Bradley Randleman, William J Dupps
PURPOSE: To assess the ability of air puff-derived biomechanical variables to predict surgeon-perceived candidacy for laser in situ keratomileusis (LASIK). SETTING: Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, and Emory Eye Institute, Emory University, Atlanta, Georgia, USA. DESIGN: Retrospective case series. METHODS: Data were collected from refractive surgery screening examinations by 2 surgeons at 2 centers...
May 15, 2018: Journal of Cataract and Refractive Surgery
Seok Hyun Yun, Dimitri Chernyak
PURPOSE OF REVIEW: Assessment of corneal biomechanics has been an unmet clinical need in ophthalmology for many years. Many researchers and clinicians have identified corneal biomechanics as source of variability in refractive procedures and one of the main factors in keratoconus. However, it has been difficult to accurately characterize corneal biomechanics in patients. The recent development of Brillouin light scattering microscopy heightens the promise of bringing biomechanics into the clinic...
May 15, 2018: Current Opinion in Ophthalmology
R Herber, N Terai, K R Pillunat, F Raiskup, L E Pillunat, E Spörl
BACKGROUND: Topographic and tomographic parameters alone are often not sufficient for early detection of corneal changes. Pathological alterations in the microstructure of the cornea occur before changes in topography and tomography can be detected. Biomechanical parameters show a strong correlation with microscopic structural changes. OBJECTIVE: The aim of the study was to gain information about the microscopic structure and consistency of the cornea by measuring biomechanical parameters...
May 16, 2018: Der Ophthalmologe: Zeitschrift der Deutschen Ophthalmologischen Gesellschaft
Jing Wang, Yanlin Ren, Kun Liang, Zhengxuan Jiang, Liming Tao
BACKGROUND: Femtosecond laser-assisted in situ keratomileusis (FS-LASIK) has gained widespread popularity as a safe, effective and predictable treatment for correcting myopia and myopic astigmatism.However, complications such as biomechanical changes, structural weakness, dry eye and induction of high-order aberrations (HOAs) have been associated with FS laser excision. The induction of HOAs has been reported to reduce quality of vision, leading to increased glare, halos, starburst and deterioration of contrast function corneal HOAs play a significant role in whole-eye aberration...
May 2018: Medicine (Baltimore)
Edward Manche, Joshua Roe
PURPOSE OF REVIEW: Laser vision correction remains an active area of research, and there have been many recent advances in the field. The purpose of this review is to provide an update on the recent advances for one of the most common methods of laser vision correction, wavefront-guided laser in-situ keratomileusis (LASIK). RECENT FINDINGS: Recent technological advancements in wavefront aberrometry are largely responsible for the improved visual outcomes that have been recently reported...
July 2018: Current Opinion in Ophthalmology
FangJun Bao, JunJie Wang, Si Cao, Na Liao, Bao Shu, YiPing Zhao, YiYu Li, XiaoBo Zheng, JinHai Huang, ShiHao Chen, QinMei Wang, Ahmed Elsheikh
To develop and validate numerical models of the laser in situ keratomileusis (LASIK) procedure through considering its effect on corneal biomechanical behavior. 3D finite element models of the human eye were developed to simulate LASIK. The models' predictions of post-operative corneal elevation, corneal refractive power with vector decomposition (M-c-pos , J0-c-pos , J45-c-pos ) and refractive error correction (M-rec , J0-rec , J45-rec ) were compared against clinical data obtained for 28 eyes of 28 patients...
July 2018: Journal of the Mechanical Behavior of Biomedical Materials
Yirui Zhu, Peter S Reinach, Hanlei Zhu, Ling Li, Fan Yang, Jia Qu, Wei Chen
PURPOSE: To determine whether the pulsed-light ultraviolet-A (UVA) accelerated corneal crosslinking (CXL) procedure is more efficacious and selective than its continuous-light counterpart in rabbits. SETTING: School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China. DESIGN: Experimental study. METHODS: Fifty-four rabbits were divided into 2 groups. Group 1 had continuous-light accelerated CXL using 9 mW/cm2 UVA for 10 minutes (5...
March 2018: Journal of Cataract and Refractive Surgery
Ryotaro Ueki, Naoyuki Maeda, Mutsumi Fuchihata, Tomoko Asai, Shizuka Koh, Hisataka Fujimoto, Masafumi Uematsu, Kohji Nishida
PURPOSE: To investigate the corneal biomechanics in eyes with keratectasia following LASIK using a dynamic Scheimpflug analyzer. DESIGN: Case-Control study. METHOD: The subjects in the study included 12 eyes with keratectasia after LASIK (KE), 24 eyes with keratoconus (KC), 17 eyes without keratectasia after LASIK (LASIK), and 34 eyes with normal corneas (Normal). Corneal biomechanics of the four groups were evaluated using a dynamic Scheimpflug analyzer...
April 26, 2018: Japanese Journal of Ophthalmology
Kai-Jung Chen, Akram Joda, Riccardo Vinciguerra, Ashkan Eliasy, Shervin Mir Mohi Sefat, Daniel Kook, Brendan Geraghty, Cynthia J Roberts, Ahmed Elsheikh
PURPOSE: To compare a biomechanically corrected intraocular pressure (bIOP) algorithm provided by the dynamic Scheimpflug analyzer (Corvis ST) with Goldmann applanation tonometry IOP (Goldmann IOP) and standard dynamic Scheimpflug analyzer IOP measurements before and after laser in situ keratomileusis (LASIK) and refractive lenticule extraction small-incision lenticule extraction (SMILE) surgeries. SETTING: Smile Eye Clinic, Munich, Germany, and University of Liverpool, Liverpool, United Kingdom...
May 2018: Journal of Cataract and Refractive Surgery
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