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Corneal Biomechanics

Mehtap Caglayan, Ozge Sarac, Pinar Kosekahya, Sukran Erten, Berna Ayan, Nurullah Cagil
PURPOSE: The aim of this study was to evaluate the corneal biomechanical parameters in patients with ankylosing spondylitis (AS) and to compare them with the healthy subjects. METHODS: Sixty patients with AS (study group) and 60 healthy subjects (control group) were enrolled in this prospective study. The study group was further classified as active (n:30) and inactive (n:30). After detailed ophthalmological examination including intraocular pressure (IOP) measurement with Goldmann applanation tonometer (IOPGAT), corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated IOP (IOPcc), and Goldmann-correlated IOP (IOPg) were measured with the Reichert Ocular Response Analyzer (ORA)...
October 5, 2016: International Ophthalmology
Atilla Suleyman Dikici, Ismail Mihmanli, Fahrettin Kilic, Ahmet Ozkok, Gokhan Kuyumcu, Pinar Sultan, Cesur Samanci, Mehmet Halit Yilmaz, Babak Rafiee, Nevbahar Tamcelik, Zehra Isik Hasiloglu, Fatih Kantarci
BACKGROUND: Primary open-angle glaucoma is a multifactorial serious disease characterized by progressive retinal ganglion cell death and loss of visual field. OBJECTIVES: The purposes of this study were to investigate shear wave elastography (SWE) use in the evaluation of the optic nerve (ON) and peripapillary structures, and to compare the findings between glaucomatous and control eyes. PATIENTS AND METHODS: A case-controlled study, including 21 patients with primary open-angle glaucoma and 21 age-matched control subjects, was carried out...
April 2016: Iranian Journal of Radiology: a Quarterly Journal Published By the Iranian Radiological Society
Fateme Alipour, Mojgan Letafatnejad, Amir Hooshang Beheshtnejad, Seyed-Farzad Mohammadi, Seyed Reza Ghaffary, Narges Hassanpoor, Mehdi Yaseri
Purpose. To evaluate the difference in biomechanical properties between contact lens induced corneal warpage and normal and keratoconic eyes. Method. Prospective observational case control study, where 94 eyes of 47 warpage suspicious and 46 eyes of 23 keratoconic patients were included. Warpage suspected cases were followed until a definite diagnosis was made (warpage, normal, or keratoconus). Results. 44 eyes of 22 patients had contact lens related corneal warpage. 46 eyes of 23 people were diagnosed as nonwarpage normal eyes...
2016: Journal of Ophthalmology
Z D Li, F J Bao, Q M Wang, J H Huang
Objective: To establish a finite-element biomechanical model of astigmatic keratotomy, and to investigate the impact of surgical parameters on corneal deformation, stress distribution and astigmatism correction. Methods: With Rhinoceros modeling and Abaqus finite element analysis software, a three-dimensional finite-element model of astigmatic cornea was developed, and surgical parameters such as incision optical zone, incision depth and length were varied. Postoperative corneal stress, apical deformation and astigmatism correction were assessed...
September 11, 2016: [Zhonghua Yan Ke za Zhi] Chinese Journal of Ophthalmology
S S Wei, Y Li, J Li, J G Liu, L Ye, Y Q Wan, J Li, J Du
Objective: To compare the corneal biomechanical properties of keratoconic and normal eyes, and to explore the changing characteristics in keratoconic eyes. Methods: Case-control study. Thirty-two keratoconic subjects(41 eyes)and 41 subjects(41 eyes)with normal corneas were enrolled in this study. Scheimpflug noncontact tonometry(Corvis ST)was performed to measure the length of Appl 1(1st A length), velocity of Appl 1(Vin), length of Appl 2(2nd A length), velocity of Appl 2(Vout), deformation amplitude(DA), peak distance, and radius...
September 11, 2016: [Zhonghua Yan Ke za Zhi] Chinese Journal of Ophthalmology
Sean McCafferty, Garrett Lim, William Duncan, Eniko Enikov, Jim Schwiegerling
PURPOSE: We evaluate solutions for an applanating surface modification to the Goldmann tonometer prism, which substantially negates the errors due to patient variability in biomechanics. METHODS: A modified Goldmann or correcting applanation tonometry surface (CATS) prism is presented which was optimized to minimize the intraocular pressure (IOP) error due to corneal thickness, stiffness, curvature, and tear film. Mathematical modeling with finite element analysis (FEA) and manometric IOP referenced cadaver eyes were used to optimize and validate the design...
September 2016: Translational Vision Science & Technology
Maryam Ali, VijayKrishna Raghunathan, Jennifer Y Li, Christopher J Murphy, Sara M Thomasy
The posterior face of the cornea consists of the corneal endothelium, a monolayer of cuboidal cells that secrete and attach to Descemet's membrane, an exaggerated basement membrane. Dysfunction of the endothelium compromises the barrier and pump functions of this layer that maintain corneal deturgesence. A large number of corneal endothelial dystrophies feature irregularities in Descemet's membrane, suggesting that cells create and respond to the biophysical signals offered by their underlying matrix. This review provides an overview of the bidirectional relationship between Descemet's membrane and the corneal endothelium...
September 14, 2016: Experimental Eye Research
William Joseph Dupps, Ibrahim Seven
PURPOSE: To investigate biomechanical strain as a structural susceptibility metric for corneal ectasia in a large-scale computational trial. METHODS: A finite element modeling study was performed using retrospective Scheimpflug tomography data from 40 eyes of 40 patients. LASIK and PRK were simulated with varied myopic ablation profiles and flap thickness parameters across eyes from LASIK candidates, patients disqualified for LASIK, subjects with atypical topography, and keratoconus subjects in 280 simulations...
August 2016: Transactions of the American Ophthalmological Society
Francisco Pérez Bartolomé, Jose María Martínez de la Casa, Irene Camacho Bosca, Federico Sáenz-Francés, Soledad Aguilar Munoa, Alberto Martín Juan, Julian Garcia-Feijoo
PURPOSE: To examine interrelations between corneal biomechanics, ocular biometric variables and optic disc size (ODS), lamina cribosa depth (LCD) or thickness (LCT) in a healthy population. MATERIAL AND METHODS: In a cross-sectional case-control study, the following measurements were made in 81 eyes of 81 participants: axial length, anterior chamber depth, lens thickness, and central corneal thickness using the optical biometer Lenstar LS900; and corneal hysteresis (CH), corneal resistance factor (CRF), Goldman-correlated intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) using the Ocular Response Analyzer...
September 14, 2016: Seminars in Ophthalmology
A Anton, M Neuburger, J F Jordan, T Wecker, J Lübke, S Heinzelmann, T Lapp, D Böhringer, T Reinhard, P Maier
INTRODUCTION: The reduction of corneal thickness following laser-assisted in-situ keratomileusis (LASIK) requires a correction of intraocular pressure (IOP) measurements. The corneal visualization Scheimpflug technology (CorVis ST, Oculus, Wetzlar, Germany) not only measures the IOP and central corneal thickness (CCT) but also determines 10 additional corneal parameters, such as the time to first and second applanation and velocity. Besides CCT we compared various corneal parameters before and after LASIK in order to detect possible correlations and to correct IOP measurements...
September 12, 2016: Der Ophthalmologe: Zeitschrift der Deutschen Ophthalmologischen Gesellschaft
S E Avetisov, V R Mamikonyan, O A Shmeleva-Demir, A A Karamyan, I A Bubnova, E E Kazaryan, N S Galoyan, A T Karapetyan
AIM: to study changes in intraocular pressure (IOP), volumetric ocular blood flow (OBF) rate, and biomechanical properties of the cornea after excimer laser ablation in patients with myopia of different degrees. MATERIAL AND METHODS: A total of 16 patients (32 eyes) with myopia ranging from 2.75 to 9.0 D were examined before and after LASIK. Ocular Blood Flow Analyzer (OBFA) was used to measure IOP and OBF as well as pulse amplitude and volume. Ocular Response Analyzer (ORA) was also employed to provide the following data: Goldmann-equivalent IOP, corneal compensated IOP, corneal hysteresis, and corneal resistance factor...
July 2016: Vestnik Oftalmologii
Alfonso Casado, Carmen Cabarga, Ane Pérez-Sarriegui, Enrique Fuentemilla
PURPOSE: To evaluate the differences in intraocular pressure (IOP) and in corneal biomechanics in eyes with uneventful nonpenetrating deep sclerectomy (NPDS) in 1 eye and with intended deep sclerectomy reconverted into trabeculectomy (RIT) in the fellow eye of the same patient. PARTICIPANTS: Forty eyes of 20 patients with both types of glaucoma surgery and more than 6 months of follow-up, and 31 eyes of 50 controls. METHODS: IOP was assessed with Goldmann applanation tonometry (GAT), ocular response analizer (ORA), and dynamic contour tonometer (DCT)...
September 2, 2016: Journal of Glaucoma
Farideh Sharifipour, Mahmoodreza Panahi-Bazaz, Roghayeh Bidar, Aida Idani, Bahman Cheraghian
PURPOSE: To determine age-related changes in corneal viscoelastic properties in healthy individuals. METHODS: This observational cross-sectional study was performed at the Department of Ophthalmology, Imam Khomeini Hospital, Ahvaz, Iran and included 302 healthy individuals in 6 age decades (range: 10-69 years). After complete ocular examination, corneal viscoelastic properties were measured by ocular response analyzer and central corneal thickness (CCT) by an ultrasonic pachymeter...
September 2016: Journal of Current Ophthalmology
Allan Luz, Fernando Faria-Correia, Marcela Q Salomão, Bernardo T Lopes, Renato Ambrósio
No abstract text is available yet for this article.
September 2016: Journal of Current Ophthalmology
Lucía Perucho-González, Federico Sáenz-Francés, Laura Morales-Fernández, José María Martínez-de-la-Casa, Carmen D Méndez-Hernández, Enrique Santos-Bueso, John L Brookes, Julián García-Feijoó
PURPOSE: To determine whether a set of ocular morphometric and biomechanical variables are able to discriminate between healthy volunteers and patients suffering from primary congenital glaucoma (PCG). METHODS: Case-control study in which 66 patients with PCG and 94 age-matched healthy subjects were evaluated using ocular response analyser (ORA) to record corneal biomechanical properties. Topographic corneal variables were obtained using the Pentacam in both groups...
August 29, 2016: Acta Ophthalmologica
Hun Lee, David Sung Yong Kang, Byoung Jin Ha, Jin Young Choi, Eung Kweon Kim, Kyoung Yul Seo, Ha Yan Kim, Tae-Im Kim
PURPOSE: To investigate the biomechanical properties of the cornea using the dynamic Scheimpflug analyzer in young healthy adults. METHODS: This prospective cross-sectional population study included 944 eyes of 472 participants aged 20 to 40 years. Participants underwent ophthalmic investigations, including evaluation of biomechanical properties of the cornea using the dynamic Scheimpflug analyzer, manifest refraction, and measurements of keratometric values by autokeratometry, intraocular pressure (IOP) by noncontact tonometer, central corneal thickness (CCT) by ultrasound, and white-to-white distance by Scheimpflug tomography...
August 24, 2016: Cornea
Hua Li, Yan Wang, Rui Dou, Pinghui Wei, Jiamei Zhang, Wei Zhao, Liuyang Li
PURPOSE: The purpose of this article was to evaluate intraocular pressure (IOP) changes and investigate the relationship with corneal biomechanics after small-incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). METHODS: A total of 193 eyes of 193 patients who underwent SMILE and FS-LASIK procedures were included in this retrospective study. Data were collected preoperatively and postoperatively, including Goldmann-correlated IOP (IOPg), corneal-compensated IOP (IOPcc), corneal hysteresis (CH), and corneal resistance factor (CRF) by ocular response analyzer, noncontact intraocular pressure (IOPNCT) by noncontact tonometer, and Ehlers, Shah, Dresden, Kohlhaas, Orssengo/Pye by the Pentacam corrected system...
August 1, 2016: Investigative Ophthalmology & Visual Science
Zhiqing Wu, Yan Wang, Jiamei Zhang, Tommy C Y Chan, Alex L K Ng, George P M Cheng, Vishal Jhanji
OBJECTIVES: To evaluate and compare the change in corneal biomechanical properties after microincision lenticule extraction (MILE) and small incision lenticule extraction (SMILE). METHODS: In this prospective study, 60 eyes received MILE surgery with 2 mm opening incision, while 64 eyes received SMILE procedure with 5 mm opening incision. Corneal hysteresis (CH), corneal resistance factor (CRF) and 37 other biomechanical waveform parameters were quantitatively assessed using ocular response analyser (ORA) preoperatively and up to 6 months postoperatively...
August 19, 2016: British Journal of Ophthalmology
Ying Hon, Kin Wan, Guo-Zhen Chen, Shu-Hao Lu, David C C Lam, Andrew K C Lam
PURPOSE: The aim of this study was to investigate the diurnal variation of corneal tangent modulus, measured using a novel corneal indentation device, in healthy Chinese subjects. METHODS: The central corneal thickness (CCT), mean central corneal radius (meanK), intraocular pressure (IOP), and corneal stiffness of 25 young adults aged 21 to 25 years (23.0 ± 1.0 yrs) were measured at 3-hour intervals from 09:00 to 21:00 in the course of 1 day. Corneal tangent modulus was calculated on the basis of corneal stiffness, CCT, and meanK...
August 17, 2016: Cornea
S H Chen, J Zhang, Y N Li, P Ding, Q M Wang
OBJECTIVE: To evaluate the effect of transepithelial corneal collagen cross-linking (CXL) in the treatment of keratoconus. METHODS: Prospective study. Sixteen eyes of 16 patients with keratoconus underwent transepithelial CXL, and the fellow eyes were considered as the controls. The mean age was (22.4±6.5) years old. In the CXL group, topical anesthesia (0.1% tetracaine) was given for 15 minutes, and 0.5% riboflavin was applied until saturated in the anterior chamber...
July 2016: [Zhonghua Yan Ke za Zhi] Chinese Journal of Ophthalmology
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