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https://www.readbyqxmd.com/read/27910295/combined-application-of-prophylactic-corneal-cross-linking-and-laser-in-situ-keratomileusis-a-review-of-literature
#1
REVIEW
Tommy C Y Chan, Alex L K Ng, Karen K W Chan, George P M Cheng, Ian Y H Wong, Vishal Jhanji
Laser in-situ keratomileusis (LASIK) is safe and effective laser refractive procedures in treating refractive errors. However, regression of treatment and iatrogenic keratectasia remain to be a major concern, especially in treating thin cornea with high ametropia. Collagen cross-linking (CXL) is an effective method in stopping keratoconus progression through increasing the biomechanical strength of the cornea. Adjuvant cross-linking to refractive procedures can theoretically help prevent regression and reduce the risk of keratectasia development by increasing the mechanical stability of cornea...
December 2, 2016: Acta Ophthalmologica
https://www.readbyqxmd.com/read/27906810/a-comparative-analysis-of-goldmann-tonometry-correction
#2
Magdalena Asejczyk-Widlicka, Wieslaw Srodka, Barbara K Pierscionek
PURPOSE: The measurement of intraocular pressure (IOP) by Goldmann applanation tonometry (GAT) is based on assumptions about corneal parameters. To correct for variations in corneal curvature and thickness, a number of equations have been proposed. This study evaluates the in vivo accuracy of these equations from individuals with primary open-angle glaucoma and compared them with measurements taken using the Pascal dynamic contour tonometer (DCT), which makes no assumptions about the corneal geometry or biomechanics...
November 30, 2016: Journal of Glaucoma
https://www.readbyqxmd.com/read/27898448/laser-vision-correction-in-treating-myopia
#3
Germano Leal Ehlke, Ronald R Krueger
Myopia is a generally benign refractive error with an increasing prevalence worldwide. It can be corrected temporarily with glasses and contact lenses and permanently with laser vision correction. The 2 main procedures currently being performed for myopia correction are photorefractive keratectomy and laser-assisted in situ keratomileusis. Each technique has its advantages, but they appear to yield similar visual outcomes 1 year after surgery. Laser vision correction for myopia was considered a paradigm shift because healthy eyes could now undergo a surgical procedure to permanently and safely correct the error by altering the center of the cornea, which was previously off limits because of the potential for loss of transparency...
November 2016: Asia-Pacific Journal of Ophthalmology
https://www.readbyqxmd.com/read/27893094/comparison-of-patient-specific-computational-modeling-predictions-and-clinical-outcomes-of-lasik-for-myopia
#4
Ibrahim Seven, Ali Vahdati, Vinicius Silbiger De Stefano, Ronald R Krueger, William J Dupps
Purpose: To assess the predictive accuracy of simulation-based LASIK outcomes. Methods: Preoperative and 3-month post-LASIK tomographic data from 20 eyes of 12 patients who underwent wavefront-optimized LASIK for myopia were obtained retrospectively. Patient-specific finite element models were created and case-specific treatment settings were simulated. Simulated keratometry (SimK) values and the mean tangential curvature of the central 3 mm (Kmean) were obtained from the anterior surfaces of the clinical tomographies, and computational models were compared...
November 1, 2016: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/27873338/high-myopes-have-lower-normalised-corneal-tangent-moduli-less-stiff-corneas-than-low-myopes
#5
Ying Hon, Guo-Zhen Chen, Shu-Hao Lu, David C C Lam, Andrew K C Lam
PURPOSE: To compare corneal tangent moduli between low and high myopes. METHODS: Corneal hysteresis (CH) and corneal resistance factor (CRF) of 32 low and 32 high myopes were obtained using an Ocular Response Analyzer, followed by a corneal indentation device that measured corneal stiffness. Corneal topography, pachymetry, Goldmann applanation tonometry intraocular pressure (GAT-IOP), and corneal compensated intraocular pressure (IOPcc) were also obtained. Corneal tangent modulus was calculated on the basis of corneal stiffness, central corneal thickness and corneal radius...
November 21, 2016: Ophthalmic & Physiological Optics: the Journal of the British College of Ophthalmic Opticians (Optometrists)
https://www.readbyqxmd.com/read/27863469/changes-in-intraocular-pressure-values-measured-with-noncontact-tonometer-nct-ocular-response-analyzer-ora-and-corvis-scheimpflug-technology-tonometer-cst-in-the-early-phase-after-small-incision-lenticule-extraction-smile
#6
Yang Shen, Xiangjian Su, Xiu Liu, Huamao Miao, Xuejun Fang, Xingtao Zhou
BACKGROUND: Corneal biomechanical properties are always compromised after corneal refractive surgeries thus leading to underestimated intraocular pressure (IOP) that complicates the management of IOP. We investigated the changes in postoperative baseline of IOP values measured with noncontact tonometer (NCT), ocular response analyzer (ORA) and corvis scheimpflug technology (CST) in the early phase after small incision lenticule extraction (SMILE). METHODS: Twenty-two eyes (-6...
November 18, 2016: BMC Ophthalmology
https://www.readbyqxmd.com/read/27847644/relationship-among-corneal-biomechanics-anterior-segment-parameters-and-geometric-corneal-parameters
#7
Sadık Görkem Çevik, Sertaç Argun Kıvanç, Berna Akova-Budak, Mediha Tok-Çevik
Purpose. To investigate the relationship between corneal biomechanical parameters, anterior segment parameters, and geometric corneal parameters in a healthy Caucasian group. Methods. This retrospective study included the healthy eyes with best corrected visual acuity of at least 20/40 of 122 Caucasian subjects. The anterior segment parameters and geometric corneal parameters such as corneal volume, central corneal thickness, horizontal and vertical corneal radii, anterior and posterior steep, and flat keratometric values were measured with a Scheimpflug camera...
2016: Journal of Ophthalmology
https://www.readbyqxmd.com/read/27830201/corneal-biomechanics-after-small-incision-lenticule-extraction-versus-q-value-guided-femtosecond-laser-assisted-in-situ-keratomileusis
#8
Jun Zhang, Li Zheng, Xia Zhao, Yang Xu, Shu Chen
PURPOSE: The aim of this study was to compare the changes in corneal biomechanical properties following small-incision lenticule extraction (SMILE) versus Q-value-guided femtosecond laser-assisted in situ keratomileusis (Q-FS-LASIK). METHODS: In this prospective comparative study, patients with a sphere plus cylinder measurement of less than -10.00 D and cylinder measurement of less than -5.00 D were included in the study. A total of 160 patients (160 eyes) with myopia and myopic astigmatism were divided into the two groups, with 80 patients (80 eyes) allocated to SMILE and 80 patients (80 eyes) allocated to Q-FS-LASIK...
December 2016: Journal of Current Ophthalmology
https://www.readbyqxmd.com/read/27803856/effect-of-femtosecond-and-microkeratome-flaps-creation-on-the-cornea-biomechanics-during-laser-in-situ-keratomileusis-one-year-follow-up
#9
Qian Sun, Zheng-Zheng Deng, Yue-Hua Zhou, Jing Zhang, Xiao-Yan Peng
AIM: To compare the corneal biomechanical outcomes at one year after laser in situ keratomileusis (LASIK) with the flaps created by Ziemer and Moria M2 microkeratome with 110 head and -20 blade. METHODS: Totally 100 eyes of 50 consecutive patients were enrolled in this prospective study and divided into two groups for corneal flaps created by ZiemerFemto LDV and Moria M2 microkeratome with 110 head and -20 blade. Corneal biomechanical properties including cornea resistance factor (CRF) and cornea hysteresis (CH) were measured before and 1, 3, 6, 12mo after surgery by ocular response analyzer...
2016: International Journal of Ophthalmology
https://www.readbyqxmd.com/read/27800259/comparison-of-changes-in-corneal-biomechanical-properties-after-photorefractive-keratectomy-and-small-incision-lenticule-extraction
#10
Yusuf Yıldırım, Onur Ölçücü, Abdurrahman Başcı, Alper Ağca, Engin Bilge Özgürhan, Cengiz Alagöz, Ali Demircan, Ahmet Demirok
OBJECTIVES: To compare the postoperative biomechanical properties of the cornea after photorefractive keratectomy (PRK) and small incision lenticule extraction (SMILE) in eyes with low and moderate myopia. MATERIALS AND METHODS: We retrospectively examined 42 eyes of 23 patients undergoing PRK and 42 eyes of 22 patients undergoing SMILE for the correction of low and moderate myopia. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with an Ocular Response Analyzer before and 6 months after surgery...
April 2016: Turkish Journal of Ophthalmology
https://www.readbyqxmd.com/read/27792759/material-properties-from-air-puff-corneal-deformation-by-numerical-simulations-on-model-corneas
#11
Nandor Bekesi, Carlos Dorronsoro, Andrés de la Hoz, Susana Marcos
OBJECTIVE: To validate a new method for reconstructing corneal biomechanical properties from air puff corneal deformation images using hydrogel polymer model corneas and porcine corneas. METHODS: Air puff deformation imaging was performed on model eyes with artificial corneas made out of three different hydrogel materials with three different thicknesses and on porcine eyes, at constant intraocular pressure of 15 mmHg. The cornea air puff deformation was modeled using finite elements, and hyperelastic material parameters were determined through inverse modeling, minimizing the difference between the simulated and the measured central deformation amplitude and central-peripheral deformation ratio parameters...
2016: PloS One
https://www.readbyqxmd.com/read/27781383/topographic-tomographic-and-biomechanical-corneal-changes-during-pregnancy-in-patients-with-keratoconus-a-cohort-study
#12
Mohammad Naderan, Ali Jahanrad
PURPOSE: This study aimed at evaluating the effect of pregnancy on topographic, tomographic and biomechanical parameters of patients with keratoconus (KC) in comparison with non-pregnant patients with KC. METHOD: In a cohort study, patients with KC, whose disease was stable for at least 2 years, were evaluated before pregnancy, at their third trimester of pregnancy (34th week of pregnancy) and 6 months after pregnancy. As the control group, an equivalent number of age- and severity-matched non-pregnant female patients with KC were evaluated at the corresponding times...
October 26, 2016: Acta Ophthalmologica
https://www.readbyqxmd.com/read/27764022/central-corneal-thickness-in-glaucoma
#13
Chelvin C A Sng, Marcus Ang, Keith Barton
PURPOSE OF REVIEW: The purpose of this review is to summarize the role of central corneal thickness (CCT) in the clinical management of a glaucoma patient. RECENT FINDINGS: The prognostic value of CCT is well recognized in patients with ocular hypertension. However, its predictive value in other glaucoma suspects and patients with established glaucoma is less certain. Tonometry artefacts can result from variations in CCT. However, an adequately validated correction algorithm for Goldmann applanation tonometry measurements does not exist...
October 19, 2016: Current Opinion in Ophthalmology
https://www.readbyqxmd.com/read/27760362/cellular-stiffness-as-a-novel-stemness-marker-in-the-corneal-limbus
#14
Tom Bongiorno, Jena L Chojnowski, James D Lauderdale, Todd Sulchek
Healthy eyes contain a population of limbal stem cells (LSCs) that continuously renew the corneal epithelium. However, each year, 1 million Americans are afflicted with severely reduced visual acuity caused by corneal damage or disease, including LSC deficiency (LSCD). Recent advances in corneal transplant technology promise to repair the cornea by implanting healthy LSCs to encourage regeneration; however, success is limited to transplanted tissues that contain a sufficiently high percentage of LSCs. Attempts to screen limbal tissues for suitable implants using molecular stemness markers are confounded by the poorly understood signature of the LSC phenotype...
October 18, 2016: Biophysical Journal
https://www.readbyqxmd.com/read/27709370/biomechanical-evaluation-of-cornea-in-patients-with-ankylosing-spondylitis
#15
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
https://www.readbyqxmd.com/read/27703662/in-vivo-evaluation-of-the-biomechanical-properties-of-optic-nerve-and-peripapillary-structures-by-ultrasonic-shear-wave-elastography-in-glaucoma
#16
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
https://www.readbyqxmd.com/read/27688908/corneal-biomechanical-findings-in-contact-lens-induced-corneal-warpage
#17
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
https://www.readbyqxmd.com/read/27647248/-finite-element-analysis-of-astigmatic-keratotomy-based-on-corneal-biomechanical-properties
#18
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
https://www.readbyqxmd.com/read/27647247/-corneal-biomechanical-properties-in-keratoconic-and-normal-eyes
#19
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
https://www.readbyqxmd.com/read/27642540/goldmann-tonometer-prism-with-an-optimized-error-correcting-applanation-surface
#20
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
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