scholarly journals On the Relationship between Corneal Biomechanics, Macrostructure and Optical Properties

2021 ◽  
Author(s):  
Francisco J. Ávila ◽  
Laura Remón ◽  
Maria Concepción Marcellán
Keyword(s):  
Optical Properties ◽  
Biomechanical Properties ◽  
Optical Quality ◽  
Optical Transparency ◽  
Optical Aberrations ◽  
Corneal Aberrations ◽  
Scheimpflug Imaging ◽  
The Hierarchical Structure ◽  
The Relationship

Optical properties of the cornea are responsible for correct vision, ultrastructure allows optical transparency and biomechanical properties governs the shape, elasticity or stiffness of the cor-nea affecting ocular integrity and intraocular pressure. Therefore, optical aberrations, corneal transparency, structure and biomechanics play a fundamental role in the optical quality of hu-man vision, ocular health and refractive surgery outcomes. However, the convergence of those properties is not yet reported at macroscopic scale within the hierarchical structure of the cornea. This work explores the relationships between biomechanics, structure and optical properties (corneal aberrations and optical density) at macrostructural level of the cornea through dual Placido-Scheimpflug imaging and air-puff tonometry systems in a healthy young adult popula-tion. Results showed convergence between optical transparency, corneal macrostructure and biomechanics.

scholarly journals On the Relationship between Corneal Biomechanics, Macrostructure, and Optical Properties

2021 ◽  
Vol 7 (12) ◽  
pp. 280
Author(s):  
Francisco J. Ávila ◽  
Maria Concepción Marcellán ◽  
Laura Remón
Keyword(s):  
Optical Properties ◽  
Spherical Aberration ◽  
Adult Population ◽  
Biomechanical Properties ◽  
Optical Quality ◽  
Human Vision ◽  
Optical Transparency ◽  
Structural Level ◽  
Corneal Aberrations ◽  
The Hierarchical Structure

Optical properties of the cornea are responsible for correct vision; the ultrastructure allows optical transparency, and the biomechanical properties govern the shape, elasticity, or stiffness of the cornea, affecting ocular integrity and intraocular pressure. Therefore, the optical aberrations, corneal transparency, structure, and biomechanics play a fundamental role in the optical quality of human vision, ocular health, and refractive surgery outcomes. However, the inter-relationships of those properties are not yet reported at a macroscopic scale within the hierarchical structure of the cornea. This work explores the relationships between the biomechanics, structure, and optical properties (corneal aberrations and optical density) at a macro-structural level of the cornea through dual Placido–Scheimpflug imaging and air-puff tonometry systems in a healthy young adult population. Results showed correlation between optical transparency, corneal macrostructure, and biomechanics, whereas corneal aberrations and in particular spherical terms remained independent. A compensation mechanism for the spherical aberration is proposed through corneal shape and biomechanics.

scholarly journals Postkeratoplasty Anterior and Posterior Corneal Surface Wavefront Analysis: Descemet’s Stripping Automated Endothelial Keratoplasty versus Penetrating Keratoplasty

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Maria L. Salvetat ◽  
Marco Zeppieri ◽  
Flavia Miani ◽  
Paolo Brusini
Keyword(s):  
Penetrating Keratoplasty ◽  
Imaging System ◽  
Case Series ◽  
Optical Quality ◽  
Endothelial Keratoplasty ◽  
Corneal Surface ◽  
Scheimpflug Imaging ◽  
Quality Of Vision ◽  
Range Test

Purpose. To compare the higher-order aberrations (HOAs) due to the anterior and posterior corneal surfaces in patients that underwent either Descemet-stripping-automated-endothelial-keratoplasty (DSAEK) or penetrating keratoplasty (PK) for endothelial dysfunction and age-matched controls. Methods. This retrospective, observational, case series included 28 patients after PK, 30 patients after DSAEK, and 30 healthy controls. A Scheimpflug imaging system was used to assess the HOAs due to the anterior and posterior corneal surfaces at 4 mm and 6 mm optical zones. Total, 3rd and 4th order HOAs were considered. Intra- and intergroup differences were assessed using the Friedman and the Kruskal-Wallis tests, respectively; paired comparisons were performed using Duncan's multiple range test. Results. Total, 3rd and 4th order HOAs due to both corneal surfaces at 4 mm and 6 mm optical zones were significantly higher in the PK group, intermediate in the DSAEK group, and lower in controls (). The most important HOAs components in both PK and DSAEK groups were trefoil and coma from the anterior corneal surface () and trefoil from the posterior corneal surface (). Conclusions. The optical quality of both corneal surfaces appeared significantly higher after DSAEK than after PK, which can increase the postoperative patient's quality of vision and satisfaction.

Optical Properties of Doped Cd1−xMnxTe

1986 ◽  
Vol 89 ◽  
Author(s):  
Y. Lansari ◽  
N. C. Giles ◽  
J. F. Schetzina ◽  
P. Becia ◽  
D. Kaiser
Keyword(s):  
Optical Properties ◽  
Low Temperature ◽  
Spectral Range ◽  
Room Temperature ◽  
Far Infrared ◽  
Optical Quality ◽  
Structural Quality ◽  
Reflectance Measurements ◽  
Low Temperature Photoluminescence

AbstractThe introduction of phosphorus and arsenic dopants into bulk Cd1−xMnx Te crystals grown by the Bridgman-Stockbarger technique has been studieA-with respect to the resulting optical properties. Samples with a Mn composition in the range 0.10 < x < 0.30, both as-grown and annealed, were investigated. A combination of room temperature transmittance and reflectance measurements over the spectral range from the ultraviolet to the far infrared has been used to gain information concerning the structural quality of the samples. Low temperature photoluminescence measurements (1.6−5 K) were used to determine optical quality and excitonic energies.

scholarly journals III-V nanowires with quantum dots: MBE growth and properties

2021 ◽  
Vol 2015 (1) ◽  
pp. 012124
Author(s):  
R R Reznik ◽  
K P Kotlyar ◽  
V O Gridchin ◽  
I V Ilkiv ◽  
A I Khrebtov ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Optoelectronic Devices ◽  
Optical Quality ◽  
Silicon Substrates ◽  
Single Photons ◽  
Mbe Growth ◽  
Pl Spectrum ◽  
Good Optical Quality

Abstract We demonstrate growth of AlGaAs NWs with GaAs QDs and InP NWs with InAsP QDs on silicon substrates. Results of GaAs QDs optical properties study have shown that these objects are sources of single photons. In case of InP NWs with InAsP QDs, the results showed that ~ 100% of homogeneously oriented NWs were formed with good optical quality of this system on a Si(111). PL spectrum peak near 1.3 μm indicates that such system is promising for optoelectronic devices.

STRUCTURAL AND OPTICAL PROPERTIES OF ZnO SYNTHESIZED BY TEMPERATURE GRADIENT THERMAL OXIDATION

2010 ◽  
Vol 17 (05n06) ◽  
pp. 497-503 ◽  
Author(s):  
F. K. YAM ◽  
S. S. TNEH ◽  
Y.-Q. CHAI ◽  
W. S. LAU ◽  
Z. HASSAN ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Temperature Gradient ◽  
Thermal Oxidation ◽  
Optical Quality ◽  
Annealing Process ◽  
Zno Thin Films ◽  
Structural And Optical Properties ◽  
Fixed Temperature

In this work, a series of polycrystalline ZnO samples have been synthesized from Zn thin films deposited on Si (100) substrates by using thermal oxidation technique. The ZnO thin film samples grown by this technique were then characterized by a variety of structural and optical characterization tools. The results revealed that the use of novel annealing process i.e. the application of temperature gradient in the thermal treatment could enhance the structural and optical quality of the ZnO thin films significantly as compared to the normal annealing process, i.e. a fixed temperature under different durations. Apart from the improvement of structural and optical properties of ZnO thin films, another striking feature of this novel annealing process was the promotion of the growth of ZnO nanostructures.

scholarly journals Changes of Corneal Wavefront Aberrations in Dry Eye Patients after Treatment with Artificial Lubricant Drops

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Ning Lu ◽  
Fangyu Lin ◽  
Zhu Huang ◽  
Qin He ◽  
Wei Han
Keyword(s):  
Dry Eye ◽  
Spherical Aberration ◽  
Optical Quality ◽  
Control Group ◽  
Eye Drops ◽  
Artificial Eye ◽  
Corneal Surface ◽  
Wavefront Aberrations ◽  
Corneal Aberrations

Purpose.To evaluate the corneal aberration changes in dry eye patients after treatment with artificial eye drops.Methods.Thirty mild to moderate dry eye patients treated with artificial eye drops and twenty comparable dry eye patients were recruited as controls. Anterior corneal aberrations over 3 mm and 5 mm analytical zones including total, 3rd to 5th high order aberrations (HOAs), spherical aberration (SA), and vertical (V-coma) and horizontal coma (H-coma) obtained from corneal topography data at baseline and 2 weeks after treatment were evaluated.Results.For 3 mm zone, trefoils, V-coma, H-coma terms, and 3rd and 5th HOAs were significantly decreased (p<0.05) in the treatment group. For 5 mm zone, instillation of eye drops reduced H-coma, SA terms, 3rd to 5th orders, and total HOAs all showed a significant decrease (p<0.05). The root mean square analysis of the Zernike terms also showed similar statistical results. For control group, all individual terms and total HOAs did not have significant changes over 3 mm and 5 mm zones (p>0.05).Conclusions.Treatment with artificial eye drops can effectively improve the corneal optical quality of dry eye patients by ameliorating the HOAs of anterior corneal surface.

scholarly journals Underwater Radiance Distributions Measured with Miniaturized Multispectral Radiance Cameras

2013 ◽  
Vol 30 (1) ◽  
pp. 74-95 ◽  
Author(s):  
David Antoine ◽  
André Morel ◽  
Edouard Leymarie ◽  
Amel Houyou ◽  
Bernard Gentili ◽  
...  
Keyword(s):  
Optical Properties ◽  
Complementary Metal Oxide Semiconductor ◽  
Optical Quality ◽  
Low Noise ◽  
Oxide Semiconductor ◽  
Significant Advance ◽  
Inherent Optical Properties ◽  
Camera Design ◽  
Radiance Distribution

Abstract Miniaturized radiance cameras measuring underwater multispectral radiances in all directions at high-radiometric accuracy (CE600) are presented. The camera design is described, as well as the main steps of its optical and radiometric characterization and calibration. The results show the excellent optical quality of the specifically designed fish-eye objective. They also show the low noise and excellent linearity of the complementary metal oxide semiconductor (CMOS) detector array that is used. Initial results obtained in various oceanic environments demonstrate the potential of this instrument to provide new measurements of the underwater radiance distribution from the sea surface to dimly lit layers at depth. Excellent agreement is obtained between nadir radiances measured with the camera and commercial radiometers. Comparison of the upwelling radiance distributions measured with the CE600 and those obtained with another radiance camera also shows a very close agreement. The CE600 measurements allow all apparent optical properties (AOPs) to be determined from integration of the radiance distributions and inherent optical properties (IOPs) to be determined from inversion of the AOPs. This possibility represents a significant advance for marine optics by tying all optical properties to the radiometric standard and avoiding the deployment of complex instrument packages to collect AOPs and IOPs simultaneously (except when it comes to partitioning IOPs into their component parts).

scholarly journals Changes of Corneal Biomechanical Properties upon Exclusive Ytt-/Sr-90 Irradiation of Pterygium

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 975
Author(s):  
Fritz Rigendinger ◽  
Daniel M. Aebersold ◽  
Zeljka Cvejic ◽  
Bojan Pajic
Keyword(s):  
Visual Quality ◽  
Biomechanical Properties ◽  
First Year ◽  
Wavefront Aberration ◽  
Human Cornea ◽  
Corneal Aberrations ◽  
Horizontal Length ◽  
Quality Of Vision ◽  
Pterygium Excision

Background: It is known that pterygia above a certain size cause astigmatism and other aberrations of the human cornea and thus impair the quality of vision. Exclusive Sr-/Ytt-90 beta irradiation is a highly effective treatment for primary pterygia. The aim of this retrospective study is to determine the extent to which higher order corneal aberrations are affected by this treatment. Methods: Evaluation of corneal topographies and wavefront aberration data of 20 primary pterygia patients generated before and at different points in time in the first year after irradiation. Additionally, the size of the pterygium was measured. Results: The study showed a significant increase in coma and triple leaf aberrations in pterygia with a horizontal length of 2 mm and more. It was also found that a pterygium size greater than 2 mm significantly induces astigmatism. Both phenomena reduce visual quality. In none of the patients could a pterygium recurrence be detected after irradiation. Conclusions: If the pterygium size is less than 2 mm, early exclusive Sr/Ytt-90 beta irradiation can be recommended. If the size is more than 2 mm, a pterygium excision 6 months after beta irradiation can be discussed.

scholarly journals Functional reorganization of sensory processing following long-term neural adaptation to optical defects

2020 ◽  
Author(s):  
Antoine Barbot ◽  
Woon-Ju Park ◽  
Ru-Yuan Zhang ◽  
Krystel R Huxlin ◽  
Duje Tadin ◽  
...  
Keyword(s):  
Sensory Processing ◽  
Visual Processing ◽  
Prolonged Exposure ◽  
Sensory Information ◽  
Optical Quality ◽  
Retinal Images ◽  
Optical Aberrations ◽  
Functional Reorganization

How we see is fundamentally limited by the eye’s optics, which determine retinal image quality and constrain neural processing. Elucidating how long-term exposure to optical defects alters visual processing is vital for understanding the human brain’s capacity for and limits of sensory plasticity. Using adaptive optics to bypass the eye’s optical aberrations, we assessed changes in visual processing in neurotypically-developed adults with keratoconus (KC)—a corneal disease causing severe optical aberrations during adulthood that cannot be fully corrected using conventional methods. As a result, KC patients are chronically exposed to degraded retinal images in their everyday life, making them an ideal model to understand how prolonged exposure to poor optical quality alters visual processing. Here, we show that when tested under similar fully-corrected optical conditions as neurotypical observers, KC patients exhibited altered contrast sensitivity, with impaired sensitivity for fine spatial details and better sensitivity for coarse spatial details. Both gains and losses in contrast sensitivity were more pronounced in patients with poorer habitual optical quality. Moreover, using an equivalent noise paradigm and a computational model of visual processing, we show that these alterations in visual processing are mediated by changes in signal enhancement of spatial frequency selective mechanisms. The present findings uncover fundamental properties of neural compensation mechanisms in response to long-term exposure to optical defects, which alter sensory processing and limit the benefits of improved optics. The outcome is a large-scale functional reorganization favoring the processing of sensory information less affected by the eye’s optics.Significance statementThe eye’s optics represent an intrinsic limit to human visual perception, determining the quality of retinal images. Neural adaptation optimizes the brain’s limited sensory processing capacity to the structure of the degraded retinal inputs, providing an exceptional quality of vision given these optical limitations. Here, we show that prolonged exposure to poor optical quality results in a functional reorganization of visual processing that favors sensory information less affected by the eye’s optics. The present study helps elucidate how optical factors shape the way the brain processes visual information. Notably, the resulting adaptive neural plasticity limits the immediate perceptual benefits of optical interventions, a factor that must be taken into consideration when treating the increasing human population affected by optical defects.

Fabrication and Optical Properties of Monodisperse Fine Zinc Oxide Nanorods

2010 ◽  
Vol 663-665 ◽  
pp. 409-412
Author(s):  
Chun Ping Li ◽  
Jian Zhang ◽  
Hua Min Yu ◽  
Xiu Juan Guo
Keyword(s):  
Optical Properties ◽  
Quantum Confinement ◽  
Zno Nanorods ◽  
Optical Quality ◽  
Zinc Oxide Nanorods ◽  
Photoluminescence Spectra ◽  
Aspect Ratios ◽  
Quantum Confinement Effects ◽  
Oxide Nanorods

Highly monodisperse ZnO nanorods were synthesized by simple solution chemical process. The produced ZnO nanorods have uniform diameters about 30 nm with average aspect ratios more than 40. Raman and photoluminescence measurements were used to examine their optical properties. Raman spectrum presents weak quantum confinement effects of the fine nanorods. Laser power-dependent photoluminescence spectra show the products have intense UV emissions with narrow full width at the half maximum (FWHM). All the performed experiments determine the good crystal and optical quality of synthesized nanorods.

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