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Corneal Biomechanics

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https://www.readbyqxmd.com/read/29451741/non-invasive-optical-method-for-real-time-assessment-of-intracorneal-riboflavin-concentration-and-efficacy-of-corneal-cross-linking
#1
Giuseppe Lombardo, Valentina Villari, Norberto Liborio Micali, Nancy Leone, Cristina Labate, Maria Penelope De Santo, Marco Lombardo
Keratoconus is the primary cause of corneal transplantation in young adults worldwide. Riboflavin/UV-A corneal cross-linking may effectively halt the progression of keratoconus if an adequate amount of riboflavin enriches the corneal stroma and is photo-oxidated by UV-A light for generating additional cross-linking bonds between stromal proteins and strengthening the biomechanics of the weakened cornea. Here we reported a UV-A theranostic prototype device for performing corneal cross-linking with the ability to assess corneal intrastromal concentration of riboflavin and to estimate treatment efficacy in real time...
February 16, 2018: Journal of Biophotonics
https://www.readbyqxmd.com/read/29429282/-problems-and-challenges-in-the-development-of-corneal-refractive-surgery
#2
Y Wang, J Li
Corneal refractive surgery, as one of the common visual correction methods, has been increasingly accepted in China. There are a large number of people in China who undergo the corneal refractive surgery due to the high incidence of myopia in the country. It is essential that the safest and most effective surgery should be used to correct refractive errors in the cases involved with relatively normal eyes and corneas. In recent years, corneal refractive surgery has been rapidly developing with new technologies and techniques emerging all the time, such as SMILE (small incision lenticule extraction) surgery, which has been extensively applied in China since five years ago when it was approved by FDA...
January 11, 2018: [Zhonghua Yan Ke za Zhi] Chinese Journal of Ophthalmology
https://www.readbyqxmd.com/read/29420326/corneal-biomechanical-properties-in-obstructive-sleep-apnea-syndrome
#3
Funda Dikkaya, Rengin Yıldırım, Sevil Karaman Erdur, Gülçin Benbir, Rukiye Aydın, Derya Karadeniz
OBJECTIVES: To investigate the corneal biomechanical properties and anterior segment parameters in patients with obstructive sleep apnea syndrome (OSAS). METHODS: Fifty-four eyes of 54 patients with OSAS and 20 eyes of 20 healthy subjects were included. Patients with mild and moderate OSAS (Respiratory Disturbance Index [RDI] <30) enrolled in group 1, those with severe OSAS (RDI≥30) in group 2 and controls in group 3. Corneal biomechanical properties including corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated intraocular pressure (IOPcc) were measured with ocular response analyzer...
February 7, 2018: Eye & Contact Lens
https://www.readbyqxmd.com/read/29416315/comparison-of-corneal-biomechanics-after-myopic-small-incision-lenticule-extraction-compared-to-lasik-an-ex-vivo-study
#4
Anastasios John Kanellopoulos
Purpose: To investigate ex vivo potentially different corneal biomechanical properties after small-incision lenticule extraction (SMILE) versus LASIK for myopic correction. Methods: Thirty human donor corneas were subjected to either myopic SMILE or femtosecond laser-assisted LASIK. Donor corneas were assigned to six investigative groups: Group A, -3.00 D (diopters) SMILE; Group B, -8.00 D SMILE; Group C, -3.00 D LASIK; and Group D, -8.00 D LASIK. Additionally, two control groups were formed: Group E, SMILE and Group F, LASIK...
2018: Clinical Ophthalmology
https://www.readbyqxmd.com/read/29408793/imaging-corneal-biomechanical-responses-to-ocular-pulse-using-high-frequency-ultrasound
#5
Elias Pavlatos, Hong Chen, Keyton Clayson, Xueliang Pan, Jun Liu
Imaging corneal biomechanical changes or abnormalities is important for better clinical diagnosis and treatment of corneal diseases. We propose a novel ultrasound-based method, called ocular pulse elastography (OPE), to image corneal deformation during the naturally occurring ocular pulse. Experiments on animal and human donor eyes, as well as synthetic radiofrequency (RF) data, were used to evaluate the efficacy of the OPE method. Using very high-frequency ultrasound (center frequency = 55 MHz), correlation-based speckle tracking yielded an accuracy of less than 10% error for axial tissue displacements of or above...
February 2018: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/29399203/3d-characterization-of-corneal-deformation-using-ultrasound-speckle-tracking
#6
Keyton Clayson, Elias Pavlatos, Yanhui Ma, Jun Liu
The three-dimensional (3D) mechanical response of the cornea to intraocular pressure (IOP) elevation has not been previously reported. In this study, we use an ultrasound speckle tracking technique to measure the 3D displacements and strains within the central 5.5 mm of porcine corneas during the whole globe inflation. Inflation tests were performed on dextran-treated corneas (treated with a 10% dextran solution) and untreated corneas. The dextran-treated corneas showed an inflation response expected of a thin spherical shell, with through-thickness thinning and in-plane stretch, although the strain magnitudes exhibited a heterogeneous spatial distribution from the central to more peripheral cornea...
November 2017: Journal of Innovative Optical Health Sciences
https://www.readbyqxmd.com/read/29392322/effect-of-uva-riboflavin-collagen-crosslinking-on-biomechanics-of-artificially-swollen-corneas
#7
Hamed Hatami-Marbini, Sandeep M Jayaram
Purpose: The purpose of this study was to characterize the relation between corneal hydration and stiffening effects of the UVA/riboflavin collagen crosslinking treatment and to investigate how artificially swelling the cornea prior to this treatment procedure affects tensile property improvement. Methods: Porcine corneas were collagen crosslinked in vitro at different hydration levels using a number of hypoosmolar and isoosmolar riboflavin solutions. Thickness of the specimens prior to crosslinking was taken as a proxy for their hydration and was used to divide them into different thickness groups...
February 1, 2018: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/29370019/can-corneal-biomechanical-properties-explain-difference-in-tonometric-measurement-in-normal-eyes
#8
Ashim Dey, Rathini Lilian David, Rashima Asokan, Ronnie George
SIGNIFICANCE: Corneal biomechanical parameters can affect intraocular pressure (IOP) measurements by different tonometers compared with Goldmann applanation tonometer. This study implies that corneal hysteresis (CH) and corneal resistance factor (CRF) better explain variability in IOP measurements. PURPOSE: The aim of this study was to evaluate the effect of corneal properties on the difference in IOP measured by the Ocular Response Analyzer (ORA), Rebound Tonometer (RBT), Dynamic Contour Tonometer (DCT), and Tono-Pen from the Goldmann applanation tonometer (GAT)...
January 25, 2018: Optometry and Vision Science: Official Publication of the American Academy of Optometry
https://www.readbyqxmd.com/read/29335093/changes-in-biomechanically-corrected-intraocular-pressure-and-dynamic-corneal-response-parameters-before-and-after-transepithelial-photorefractive-keratectomy-and-femtosecond-laser-assisted-laser-in%C3%A2-situ-keratomileusis
#9
Hun Lee, Cynthia J Roberts, Tae-Im Kim, Renato Ambrósio, Ahmed Elsheikh, David Sung Yong Kang
PURPOSE: To evaluate the changes in biomechanically corrected intraocular pressure (IOP) and new dynamic corneal response parameters measured by a dynamic Scheimpflug analyzer before and after transepithelial photorefractive keratectomy (PRK) and femtosecond laser-assisted laser in situ keratomileusis (LASIK). SETTING: Yonsei University College of Medicine and Eyereum Eye Clinic, Seoul, South Korea. DESIGN: Retrospective case series. METHODS: Medical records of patients having transepithelial PRK or femtosecond-assisted LASIK were examined...
December 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/29334923/relationship-between-corneal-biomechanical-properties-and-structural-biomarkers-in-patients-with-normal-tension-glaucoma-a-retrospective-study
#10
Keunheung Park, Jonghoon Shin, Jiwoong Lee
BACKGROUND: We evaluated the relationships between corneal biomechanical properties and structural parameters in patients with newly diagnosed, untreated normal-tension glaucoma (NTG). METHODS: All subjects were evaluated using an Ocular Response Analyzer (ORA) measuring corneal hysteresis (CH) and the corneal resistance factor (CRF). Central corneal thickness (CCT), Goldmann applanation tonometric (GAT) data, axial length, and the spherical equivalent (SE), were also measured...
January 15, 2018: BMC Ophthalmology
https://www.readbyqxmd.com/read/29318768/use-of-instrumented-indentation-for-determination-of-mechanical-properties-of-human-cornea-after-uva-crosslinking
#11
Jiri Nohava, Michael Swain, Stefan J Lang, Philip Maier, Sonja Heinzelmann, Thomas Reinhard, Philipp Eberwein
UVA-crosslinking is used for treatment of corneal diseases such as keratoconus in order to stabilize the corneal tissue by crosslinking of the collagen fibers. It has been shown that the crosslinking treatment leads to a stiffening of the central corneal tissue. However, knowledge of lateral extent of the corneal stiffening as well as a systematic study of the mechanical response of human cornea is still missing. In our study we measured the stiffness (elastic modulus) of the anterior surface of healthy and crosslinked human corneas by instrumented indentation using a spherical indenter...
January 10, 2018: Journal of Biomedical Materials Research. Part A
https://www.readbyqxmd.com/read/29315446/erratum-for-in-vivo-early-corneal-biomechanical-changes-after-corneal-cross-linking-in-patients-with-progressive-keratoconus
#12
(no author information available yet)
No abstract text is available yet for this article.
January 1, 2018: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/29315442/changes-in-corneal-biomechanical-properties-with-different-corneal-cross-linking-irradiances
#13
FangJun Bao, YaRu Zheng, Chang Liu, XiaoBo Zheng, YiPing Zhao, Yuan Wang, LinNa Li, QinMei Wang, ShiHao Chen, Ahmed Elsheikh
PURPOSE: To evaluate whether different corneal cross-linking (CXL) irradiances, all with the same delivered total energy, achieve similar increases in corneal material stiffness. METHODS: One hundred twenty-six healthy white Japanese rabbits were randomly divided into seven groups (n = 18 each). After removing the epithelium of the left corneas, six groups were exposed to riboflavin (0.22% concentration by volume) and ultraviolet-A (370 nm) at different CXL irradiations, all with the same total dose (5...
January 1, 2018: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/29297099/assessment-of-corneal-biomechanical-properties-with-inflation-test-using-optical-coherence-tomography
#14
Like Wang, Lei Tian, Yanping Huang, Yifei Huang, Yongping Zheng
Biomechanical properties are important for the cornea to maintain its normal shape and function. There is still a need to develop better methods for accurate measurement of corneal mechanical properties. In this study, we propose to introduce the optical coherence tomography (OCT) in inflation test for the imaging of corneal deformation in order to measure its biomechanical properties. Ten cornea-mimicking silicone phantoms with different stiffness and five fresh porcine corneas were tested using the proposed method...
January 2, 2018: Annals of Biomedical Engineering
https://www.readbyqxmd.com/read/29284455/visual-rehabilitation-in-moderate-keratoconus-combined-corneal-wavefront-guided-transepithelial-photorefractive-keratectomy-and-high-fluence-accelerated-corneal-collagen-cross-linking-after-intracorneal-ring-segment-implantation
#15
Hun Lee, David Sung Yong Kang, Byoung Jin Ha, Jin Young Choi, Eung Kweon Kim, Kyoung Yul Seo, Tae-Im Kim
BACKGROUND: To investigate the effects of combined corneal wavefront-guided transepithelial photorefractive keratectomy (tPRK) and accelerated corneal collagen cross-linking (CXL) after intracorneal ring segment (ICRS) implantation in patients with moderate keratoconus. METHODS: Medical records of 23 eyes of 23 patients undergoing combined tPRK and CXL after ICRS implantation were retrospectively analyzed. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (MRSE), corneal indices based on Scheimpflug tomography, higher-order aberrations (HOAs), and corneal biomechanical properties were evaluated before and after ICRS implantation, and at 1, 3, and 6 months after combined tPRK and CXL...
December 29, 2017: BMC Ophthalmology
https://www.readbyqxmd.com/read/29283900/corneal-biomechanical-properties-and-central-corneal-thickness-in-pediatric-noninfectious-uveitis-a-controlled-study
#16
Emine Sen, Melike Balikoglu-Yilmaz, Pinar Ozdal
OBJECTIVE: To compare the corneal biomechanics, intraocular pressure (IOP), and central corneal thickness (CCT) of 37 patients with pediatric noninfectious uveitis with 36 healthy children. METHODS: Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated and corneal-compensated IOP (IOPg and IOPcc, respectively), and CCT were measured. RESULTS: The mean CRF was significantly lower in the pediatric uveitic eyes than controls (9...
December 27, 2017: Eye & Contact Lens
https://www.readbyqxmd.com/read/29283679/influence-of-short-term-orthokeratology-to-corneal-tangent-modulus-a-randomized-study
#17
Andrew Kc Lam, Stanley Yy Leung, Ying Hon, Lu Shu-Ho, Kit-Ying Wong, Pui-Kwan Tiu, David Cc Lam
PURPOSE: Influence of orthokeratology on corneal biomechanics is equivocal using Ocular Response Analyzer, ORA. Implementing indentation method, corneal tangent modulus was measured and monitored in short-term orthokeratology. MATERIALS AND METHODS: Sixteen young subjects with refractive errors between -4D to -5D sphere and astigmatism within -1.50D were recruited. One randomly selected eye wore orthokeratology lens (treatment), and the fellow eye wore conventional rigid gas permeable lens (control)...
December 28, 2017: Current Eye Research
https://www.readbyqxmd.com/read/29283117/refractive-lenticule-extraction-small-incision-lenticule-extraction-a-new-refractive-surgery-paradigm
#18
REVIEW
Sri Ganesh, Sheetal Brar, Raghavender Reddy Arra
Small incision lenticule extraction (SMILE), a variant of refractive lenticule extraction technology is becoming increasingly popular, as a flapless and minimally invasive form of laser vision correction (LVC) for the treatment of myopia and myopic astigmatism. This review aims at summarizing the principles, surgical technique, and clinical outcomes in terms of visual and refractive results, safety, efficacy, postoperative dry eye, aberrations, and biomechanics of SMILE and its comparison with other conventional techniques of LVC, such as laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK)...
January 2018: Indian Journal of Ophthalmology
https://www.readbyqxmd.com/read/29246498/epithelium-derived-mir-204-inhibits-corneal-neovascularization
#19
Xiaoping Zhang, Guohu Di, Muchen Dong, Mingli Qu, Xiaowen Zhao, Haoyun Duan, Xiaoli Hu, Ting Liu, Qingjun Zhou, Weiyun Shi
MicroRNA-204 (miR-204) is highly expressed in cornea, here we explored the role and mechanism of miR-204 in corneal neovascularization (CNV). Mouse CNV was induced by intrastromal placement of suture in BALB/c mice with the subconjunctival injection of miR-204 agomir or negative control. Human primary limbal epithelial cells (LECs) and immortalized microvascular endothelial cells (HMECs) were used to evaluate the expression changes and anti-angiogenic effects of miR-204 under biomechanical stress (BS). The expression and localization of miR-204, vascular endothelial growth factor (VEGF) and their receptors were detected by quantitative real-time PCR, in situ hybridization, immunohistochemistry and Western blot...
December 12, 2017: Experimental Eye Research
https://www.readbyqxmd.com/read/29242757/differential-gene-transcription-of-extracellular-matrix-components-in-response-to-in-vivo-corneal-crosslinking-cxl-in-rabbit-corneas
#20
Sabine Kling, Arthur Hammer, Emilio A Torres Netto, Farhad Hafezi
Purpose: We studied changes in gene transcription after corneal crosslinking (CXL) in the rabbit cornea in vivo and identified potential molecular signaling pathways. Methods: A total of 15 corneas of eight male New-Zealand-White rabbits were de-epithelialized and equally divided into five groups. Group 1 served as an untreated control. Groups 2 to 5 were soaked with 0.1% riboflavin for 20 minutes, which in Groups 3 to 5 was followed by UV-A irradiation at a fluence of 5...
December 2017: Translational Vision Science & Technology
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