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Alexander H Ward, Thomas T Norton, Carrie E Huisingh, Timothy J Gawne
During postnatal refractive development, an emmetropization mechanism uses refractive error to modulate the growth rate of the eye. Hyperopia (image focused behind the retina) produces what has been described as "GO" signaling that increases growth. Myopia (image focused in front of the retina) produces "STOP" signaling that slows growth. The interaction between GO and STOP conditions is non-linear; brief daily exposure to STOP counteracts long periods of GO. In young tree shrews, long-wavelength (red) light, presented 14 h per day, also appears to produce STOP signals...
April 12, 2018: Vision Research
Kenichi Fujii, Rika Kawakami, Seiichi Hirota
Optical coherence tomography (OCT), a catheter-based imaging modality for the visualization of coronary arteries, is widely used during percutaneous coronary intervention to improve the understanding of the anatomy of coronary artery stenosis and to elucidate the mechanisms of atherosclerosis. In this review, we provide a short description of the histopathological validations of OCT for visualizing atherosclerotic plaques and vascular healing response after drug-eluting stent (DES) implantation. Because OCT measures the intensity of light returning from within a tissue, tissue having a higher heterogeneity of optical index of refraction, such as microcalcification deposition and foam cell accumulation on the luminal surface, may exhibit stronger optical scattering that appears as a thin-cap fibroatheroma image...
April 11, 2018: Journal of Cardiology
David J Glugla, Madeline B Chosy, Marvin D Alim, Kimberly K Childress, Amy C Sullivan, Robert R McLeod
We demonstrate that multiple exposures of a two-component holographic photopolymer can quadruple the refractive index contrast of the material beyond the single-exposure saturation limit. Quantitative phase microscopy of isolated structures written by laser direct-write lithography is used to characterize the process. This technique reveals that multiple exposures are made possible by diffusion of the chemical components consumed during writing into the previously exposed regions. The ultimate index contrast is shown to be limited by the solubility of fresh components into the multiply exposed region...
April 15, 2018: Optics Letters
Yuebian Zhang, Wenwei Liu, Zhancheng Li, Zhi Li, Hua Cheng, Shuqi Chen, Jianguo Tian
We design and numerically analyze a high-quality (Q)-factor, high modulation depth, multiple Fano resonance device based on periodical asymmetric paired bars in the near-infrared regime. There are four sharp Fano peaks arising from the interference between subradiant modes and the magnetic dipole resonance mode that can be easily tailored by adjusting different geometric parameters. The maximal Q-factor can exceed 105 in magnitude, and the modulation depths ΔT can reach nearly 100%. Combining the narrow resonance line-widths with strong near-field confinement, we demonstrate an optical refractive index sensor with a sensitivity of 370 nm/RIU and a figure of merit of 2846...
April 15, 2018: Optics Letters
Cyril Bernerd, Patricia Segonds, Jérôme Debray, Takashi Notake, Mio Koyama, Hiroaki Minamide, Hiromasa Ito, Benoît Boulanger
We performed the direct measurement of second harmonic generation and sum frequency generation phase-matching directions in the organic N-benzyl-2-methyl-4-nitroaniline crystal over its visible and near-infrared transparency range. The fit of these data allowed us to refine the Sellmeier equations of the three principal refractive indices in this range. With these equations, we improved the calculated tuning curves of terahertz emission from a phase-matched difference frequency process. We also determined the absolute magnitude of the d24 nonlinear coefficient...
April 15, 2018: Optics Letters
Chaoyou Tao, Xinshu Zou, Kai Du, Lin Zhang, Hongwei Yan, Xiaodong Yuan
Shape-tunable hollow silica nanomaterials, including hollow silica nano-spheres and nano-tadpoles, were synthesized with a one-step soft-templating method. A possible particle growth mechanism was proposed. Films were built from these shape-tunable hollow silica nanomaterials with refractive indices as low as 1.045, which is, to the best of our knowledge, the third-lowest value ever reported so far. For the first time, the refractive indices of films were tuned by changing the morphology of building blocks...
April 15, 2018: Optics Letters
Jiawen Li, Erik Schartner, Stefan Musolino, Bryden C Quirk, Rodney W Kirk, Heike Ebendorff-Heidepriem, Robert A McLaughlin
The ability to visualize structure while simultaneously measuring chemical or physical properties of a biological tissue has the potential to improve our understanding of complex biological processes. We report the first miniaturized single-fiber-based imaging+sensing probe capable of simultaneous optical coherence tomography (OCT) imaging and temperature sensing. An OCT lens is fabricated at the distal end of a double-clad fiber, including a thin layer of rare-earth-doped tellurite glass to enable temperature measurements...
April 15, 2018: Optics Letters
Jean-Michel Desse, François Olchewsky
This Letter proposes a dual-reference digital holographic interferometer for analyzing the high refractive index encountered in transonic and supersonic flows. For that, a Wollaston prism is inserted in the reference arm in order to simultaneously generate two orthogonally polarized reference waves. As a consequence, recorded interferograms contain two crossed and perpendicular interference patterns that give two orders fully separated in the Fourier spectrum. It is then possible to analyze a transparent object regardless of the orientation of the refractive index gradient using the two phase maps reconstructed with each of the two first interference orders...
April 15, 2018: Optics Letters
Alexander K Schuster, Heike M Elflein, Alexander Rommel, Laura Krause, Norbert Pfeiffer, Michael S Urschitz
BACKGROUND: Vision-relevant refractive errors in children require regular ophthalmological control examinations. In this study we estimated the prevalence of wearing glasses for children and adolescents in Germany and the frequency of ophthalmological care. METHODS: We analyzed data of the German Health Interview and Examination Survey for Children and Adolescents (KiGGS, baseline survey 2003-2006, N = 17,640). Wearing glasses was documented from the age of 3 years in the examination part...
April 12, 2018: Der Ophthalmologe: Zeitschrift der Deutschen Ophthalmologischen Gesellschaft
Asuka Takeyama, Kyoko Ishida, Ayako Anraku, Masahiro Ishida, Goji Tomita
Purpose: To compare optical coherence tomography angiography (OCT-A) and laser speckle flowgraphy (LSFG) for the diagnosis of normal-tension glaucoma (NTG). Methods: Twenty-eight eyes of 28 patients with NTG and 25 eyes of 25 normal subjects matched for age, refractive errors, systemic blood pressure, and central corneal thickness were evaluated. OCT-A was used to measure whole image vessel density, inside disc vessel density, and peripapillary vessel density; using LSFG, mean blur rate (MBR) inside the whole optic nerve head (ONH) area (MBRA ), and MBR of the vessel area (MBRV ) and tissue area (MBRT ) inside the ONH, were determined...
2018: Journal of Ophthalmology
Haris Apriyanto, Gautier Ravet, Olivier D Bernal, Michel Cattoen, Han Cheng Seat, Valérie Chavagnac, Frederic Surre, James H Sharp
We propose and develop a comprehensive model for estimating the refractive index (RI) response over three potential sensing zones in a multimode fiber. The model has been developed based on a combined ray optics, Gaussian beam, and wave optics analysis coupled to the consideration of the injected interrogating lightwave characteristics and validated experimentally through the realization of three sensors with different lengths of stripped cladding sections as the sensing region. The experimental results highly corroborate and validate the simulation output from the model for the three RI sensing zones...
April 12, 2018: Scientific Reports
Yoshihiro Ue, Hiromu Monai, Kaori Higuchi, Daisuke Nishiwaki, Tetsuya Tajima, Kenya Okazaki, Hiroshi Hama, Hajime Hirase, Atsushi Miyawaki
The high-resolution in vivo imaging of mouse brain for quantitative analysis of fine structures, such as dendritic spines, requires objectives with high numerical apertures (NAs) and long working distances (WDs). However, this imaging approach is often hampered by spherical aberration (SA) that results from the mismatch of refractive indices in the optical path and becomes more severe with increasing depth of target from the brain surface. Whereas a revolving objective correction collar has been designed to compensate SA, its adjustment requires manual operation and is inevitably accompanied by considerable focal shift, making it difficult to acquire the best image of a given fluorescent object...
April 9, 2018: Biochemical and Biophysical Research Communications
Shahrokh Ramin, Azad Sangin Abadi, Farideh Doroodgar, Mehrdad Esmaeili, Faizollah Niazi, Sana Niazi, Cyrus Alinia, Yaser Golestani, Reza Taj Abadi
This study was performed to evaluate the visual, refractive, and aberration measurement results of 2 implants, including Intacs Intracorneal Ring Segments (ICRS) and phakic Toric Implantable Collamer Lens (TICL), in patients with moderate Keratoconus (KCN). In this retrospective cross-sectional study, 30 patients with KCN with a mean age of 29.83 years were included in 2 groups, including the Intacs Intracorneal Ring Segments (ICRS) group and the phakic Toric Implantable Collamer Lens (TICL) group. Preoperative data as well as 6-month, 1-, 2-, 3- and 4-year follow-up data after the operation were collected and analyzed with the SPSS software (ver...
2018: Medical Hypothesis, Discovery and Innovation in Ophthalmology
Majid Moshirfar, Jordan D Desautels, Brian D Walker, Michael S Murri, Orry C Birdsong, Phillip C Hoopes
Laser vision correction is a safe and effective method of reducing spectacle dependence. Photorefractive Keratectomy (PRK), Laser In Situ Keratomileusis (LASIK), and Small-Incision Lenticule Extraction (SMILE) can accurately correct myopia, hyperopia, and astigmatism. Although these procedures are nearing optimization in terms of their ability to produce a desired refractive target, the long term cellular responses of the cornea to these procedures can cause patients to regress from the their ideal postoperative refraction...
2018: Medical Hypothesis, Discovery and Innovation in Ophthalmology
Feng Zhao, Tian Han, Xun Chen, Zhi Chen, Ke Zheng, Xiaoying Wang, Xingtao Zhou
OBJECTIVES: To evaluate the relationship between pupillary response to light, myopia and disk halo size. DESIGN: Cross-sectional study. SETTING: Single refractive surgery centre. PARTICIPANTS: In this study, 197 right eyes of 197 patients between 20 and 35 years of age were evaluated for disk halo size and pupillary response to light with a vision monitor. PRIMARY AND SECONDARY OUTCOME MEASURES: Halo radius, age, spherical equivalent (SE), axial length (AL), initial diameter, amplitude of contraction, latency of contraction, duration of contraction, velocity of contraction, latency of dilation, duration of dilation, velocity of dilation, maximum pupil, minimum pupil, average pupil and dark pupil...
April 10, 2018: BMJ Open
Zhaopeng Meng, Xiaoyu Zhai, Jianguo Wei, Zhiyang Wang, Hanzhong Wu
In this paper, we demonstrate a method using a frequency comb, which can precisely measure the refractive index of water. We have developed a simple system, in which a Michelson interferometer is placed into a quartz-glass container with a low expansion coefficient, and for which compensation of the thermal expansion of the water container is not required. By scanning a mirror on a moving stage, a pair of cross-correlation patterns can be generated. We can obtain the length information via these cross-correlation patterns, with or without water in the container...
April 9, 2018: Sensors
Michael J Doughty
PURPOSE: To evaluate whether visual target character and visibility affects spontaneous eye blink rate (SEBR) in primary eye gaze and silence. METHODS: Video recordings were made of young healthy adults who were either emmetropic (n=32) or who wore spectacles for refractive error (range -4.75D and +4.50D (n=31). Emmetropes had 5min recordings made whilst seated and looking towards a distant whiteboard. For spectacle wearers, recordings were made whilst looking towards the whiteboard with a 35mm sized cross, and repeated after spectacle removal...
April 4, 2018: Journal of Optometry
Svetlana Korneychuk, Bart Partoens, Giulio Guzzinati, Rajesh Ramaneti, Joff Derluyn, Ken Haenen, Jo Verbeeck
A technique to measure the band gap of dielectric materials with high refractive index by means of energy electron loss spectroscopy (EELS) is presented. The technique relies on the use of a circular (Bessel) aperture and suppresses Cherenkov losses and surface-guided light modes by enforcing a momentum transfer selection. The technique also strongly suppresses the elastic zero loss peak, making the acquisition, interpretation and signal to noise ratio of low loss spectra considerably better, especially for excitations in the first few eV of the EELS spectrum...
March 29, 2018: Ultramicroscopy
Hassan Hashemi, Amir Asharlous, Abbasali Yekta, Hadi Ostadimoghaddam, Masumeh Mohebi, Mohamadreza Aghamirsalim, Mehdi Khabazkhoob
PURPOSE: To evaluate the relationship patterns between astigmatism axes of fellow eyes (rule similarity and symmetry) and to determine the prevalence of each pattern in the studied population. METHODS: This population-based study was conducted in 2015 in Iran. All participants had tests for visual acuity, objective refraction, subjective refraction (if cooperative), and assessment of eye health at the slit-lamp. Axis symmetry was based on two different patterns: direct (equal axes) and mirror (mirror image symmetry) or enantiomorphism...
April 3, 2018: Journal of Optometry
Nauman Hashmani, Sharif Hashmani, Choudhry M Saad
Purpose: To map the corneal epithelium using a map measuring 9 mm in diameter and view the effects of age, sex, and axial length. Additionally, we wanted to demonstrate the reproducibility of this technique. Methods: We calculated the epithelial thickness in 220 individuals using an SD-OCT machine with the newly released commercially available algorithm. We included normal eyes with refractive errors between +5 and -6 diopters (D). We excluded patients with an intraocular pressure of >22 mm Hg, history of cataract, previous ocular surgery, or disease and those with corneal pathology...
March 1, 2018: Investigative Ophthalmology & Visual Science
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