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Hema Radhakrishnan, W Neil Charman
PURPOSE: To establish the optical performance of currently available Alvarez variable-power spectacles in relation to their possible utility for ametropes and presbyopes. METHODS: Two commercial designs of variable-power (variable-focus) spectacles were studied: FocusSpecs and Adlens Adjustables. Using focimetry, power and prism at three different power settings were measured across the aperture of the lenses of each design and local optical quality was explored in more detail using interferometry...
February 17, 2017: Ophthalmic & Physiological Optics: the Journal of the British College of Ophthalmic Opticians (Optometrists)
Ercüment Bozkurt, Engin Bilge Ozgurhan, Betul Ilkay Sezgin Akcay, Tugba Kurt, Yusuf Yildirim, Zehra Karaagaç Günaydin, Ahmet Demirok
Purpose. To report the visual, refractive, and corneal topography and wavefront aberration results of accelerated corneal cross-linking (CXL) during a 24-month follow-up. Methods. Forty-seven eyes underwent riboflavin-ultraviolet A-induced accelerated CXL treatment (30 mW/cm(2) with a total dose of 7.2 joules/cm(2)). Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical and cylindrical values, keratometry (K) measurements (Ksteep, Kflat, Kavg, and Kapex), central corneal thickness, and anterior corneal aberrometric analyses including total wavefront error (WFE), total high order aberration (HOA), astigmatism, trefoil, coma, quadrafoil, secondary astigmatism, and spherical aberration were evaluated...
2017: Journal of Ophthalmology
Guus A de Waard, Carlo Di Mario, Amir Lerman, Patrick W Serruys, Niels van Royen
Determining the optimal treatment strategy for revascularization of coronary artery stenosis involves the use of fractional flow reserve (FFR). To improve the low clinical uptake of physiological lesion assessment to guide revascularization, the instantaneous wave-free period (iFR) was proposed as a simpler alternative to FFR that does not require adenosine administration. iFR is calculated as the ratio of blood pressure distal and proximal to a coronary artery stenosis during the diastolic wave- free period...
February 14, 2017: EuroIntervention
JunJie Piao, Ying-Jun Li, Woong-Joo Whang, Mihyun Choi, Min Ji Kang, Jee Hye Lee, Geunyoung Yoon, Choun-Ki Joo
PURPOSE: To compare the visual and refractive outcomes after laser-assisted in situ keratomileusis (LASIK) surgery for correction of myopia or myopic astigmatism using a six-dimensional Amaris excimer laser. METHODS: In this retrospective cohort study, we enrolled 47 eyes of 28 patients (age: 19-36 years) with myopia or myopic astigmatism. We used the Custom Ablation Manager protocol and performed ablations with the SCHWIND AMARIS system. LASIK flaps were cut with an iFS Advanced Femtosecond Laser...
2017: PloS One
Francesco Monticone, Andrea Alù
The field of metamaterials has opened landscapes of possibilities in basic science, and a paradigm shift in the way we think about and design emergent material properties. In many scenarios, metamaterial concepts have helped overcome long-held scientific challenges, such as the absence of optical magnetism and the limits imposed by diffraction in optical imaging. As the potential of metamaterials, as well as their limitations, become clearer, these advances in basic science have started to make an impact on several applications in different areas, with far-reaching implications for many scientific and engineering fields...
February 6, 2017: Reports on Progress in Physics
E Jankowska, S Drobczynski, C S Menoni
We demonstrate a method based on carrier frequency interferometry (CFI) that measures surface deformation with high accuracy. The method is applied to assess the deformation of thin-film dielectrics deposited on thick substrates. CFI measured the wavefront radius of curvature R with an accuracy of 0.2% for an R smaller than 500 m and 2% for an R between 500 and 2000 m (flat reference substrate). We show the method has a significantly larger dynamic range and sensitivity than Twyman-Green and comparable sensitivity to white light interferometry...
February 1, 2017: Applied Optics
Nazmul Hasan, Aishwaryadev Banerjee, Hanseup Kim, Carlos H Mastrangelo
We demonstrate the implementation of a compact tunable-focus liquid lens suitable for adaptive eyeglass application. The lens has an aperture diameter of 32 mm, optical power range of 5.6 diopter, and electrical power consumption less than 20 mW. The lens inclusive of its piezoelectric actuation mechanism is 8.4 mm thick and weighs 14.4 gm. The measured lens RMS wavefront aberration error was between 0.73 µm and 0.956 µm.
January 23, 2017: Optics Express
P Pozzi, D Wilding, O Soloviev, H Verstraete, L Bliek, G Vdovin, M Verhaegen
The quality of fluorescence microscopy images is often impaired by the presence of sample induced optical aberrations. Adaptive optical elements such as deformable mirrors or spatial light modulators can be used to correct aberrations. However, previously reported techniques either require special sample preparation, or time consuming optimization procedures for the correction of static aberrations. This paper reports a technique for optical sectioning fluorescence microscopy capable of correcting dynamic aberrations in any fluorescent sample during the acquisition...
January 23, 2017: Optics Express
A Denoeud, L Chopineau, A Leblanc, F Quéré
Laser beams carrying orbital angular momentum (OAM) have found major applications in a variety of scientific fields, and their potential for ultrahigh-intensity laser-matter interactions has since recently been considered theoretically. We present an experiment where such beams interact with plasma mirrors up to laser intensities such that the motion of electrons in the laser field is relativistic. By measuring the spatial intensity and phase profiles of the high-order harmonics generated in the reflected beam, we obtain evidence for the helical wavefronts of the high-intensity laser at focus, and study the conservation of OAM in highly nonlinear optical processes at extreme laser intensities...
January 20, 2017: Physical Review Letters
Ben-Yi Wang, Lu Han, Yang Yang, Qing-Yang Yue, Cheng-Shan Guo
A wavefront sensing method based on a spatial light modulator (SLM) and an incremental binary random sampling (IBRS) algorithm is proposed. In this method, the recording setup is built just by a transmittance SLM and an image sensor. The tested wavefront incident to the SLM plane can be quantitatively retrieved from the diffraction intensities of the wavefront passed through the SLM displaying a IBRS pattern. Because only two modulation states (opaque and transparent) of the SLM are used, the method does not need to know the concrete modulation function of the SLM in advance...
February 1, 2017: Optics Letters
Jongchan Park, Chunghyun Park, KyeoReh Lee, Yong-Hoon Cho, YongKeun Park
Due to its time-reversal nature, optical phase conjugation generates a monochromatic light wave which retraces its propagation paths. Here, we demonstrate the regeneration of a subwavelength optical focus by phase conjugation. Monochromatic light from a subwavelength source is scattered by random nanoparticles, and the scattered light is phase conjugated at the far-field region by coupling its wavefront into a single-mode optical reflector using a spatial light modulator. Then the conjugated beam retraces its propagation paths and forms a refocus on the source at the subwavelength scale...
January 30, 2017: Scientific Reports
Tahseen Kamal, Rachel Watkins, Zijian Cen, Jaden Rubinstein, Gary Kong, Woei Ming Lee
Moldless lens manufacturing techniques using standard droplet dispensing technology often require precise control over pressure to initiate fluid flow and control droplet formation. We have determined a series of interfacial fluid parameters optimised using standard 3D printed tools to extract, dispense and capture a single silicone droplet that is then cured to obtain high quality lenses. The dispensing process relies on the recapitulation of liquid dripping action (Rayleigh-Plateau instability) and the capturing method uses the interplay of gravitational force, capillary forces and liquid pinning to control the droplet shape...
January 27, 2017: Scientific Reports
Sergei Nechaev, Kirill Polovnikov
Optimal buckling of a tissue, e.g. a plant leaf, growing by means of exponential division of its peripheral cells, is considered in the framework of a conformal approach. It is shown that the boundary profile of a tissue is described by the 2D eikonal equation, which provides the geometric optic approximation for the wavefront propagating in a medium with an inhomogeneous refraction coefficient. A variety of optimal surfaces embedded in 3D is controlled by spatial dependence of the refraction coefficient which, in turn, is dictated by the local growth protocol...
January 25, 2017: Soft Matter
Majid Moshirfar, Tirth J Shah, David Franklin Skanchy, Steven H Linn, Paul Kang, Daniel S Durrie
PURPOSE: To compare and analyze the differences in visual outcomes between Visx iDesign Advanced WaveScan Studio™ System, Alcon Wavelight Allegro Topolyzer and Nidek EC-5000 using Final Fit™ Custom Ablation Treatment Software from the submitted summary of safety and effectiveness of the US Food and Drug Administration (FDA) data. METHODS: In this retrospective comparative study, 334 eyes from Visx iDesign, 212 eyes from Alcon Contour, and 135 eyes from Nidek CATz platforms were analyzed for primary and secondary visual outcomes...
2017: Clinical Ophthalmology
Christos G Bampis, Petros Maragos, Alan C Bovik
We propose graph-driven approaches to image segmentation by developing diffusion processes defined on arbitrary graphs. We formulate a solution to the image segmentation problem modeled as the result of infectious wavefronts propagating on an image-driven graph where pixels correspond to nodes of an arbitrary graph. By relating the popular Susceptible - Infected - Recovered epidemic propagation model to the Random Walker algorithm, we develop the Normalized Random Walker and a lazy random walker variant. The underlying iterative solutions of these methods are derived as the result of infections transmitted on this arbitrary graph...
October 26, 2016: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
Chih-Wei Chang, Yue-Loong Hsin, Wentai Liu
Mapping the electric field of the brain with electrodes benefits from its superior temporal resolution but is prone to low spatial resolution property comparing with other modalities such as fMRI, which can directly impact the precision of clinical diagnosis. Simulations show that dense arrays with straightforwardly miniaturized electrodes in terms of size and pitch may not improve the spatial resolution but only strengthen the cross coupling between adjacent channels due to volume conduction. We present a new spatially focused method to improve the electrode spatial selectivity and consequently suppress the neural signal coupling from the sources in the vicinity...
March 7, 2016: IEEE Transactions on Neural Systems and Rehabilitation Engineering
James Polans, Brenton Keller, Oscar M Carrasco-Zevallos, Francesco LaRocca, Elijah Cole, Heather E Whitson, Eleonora M Lad, Sina Farsiu, Joseph A Izatt
The peripheral retina of the human eye offers a unique opportunity for assessment and monitoring of ocular diseases. We have developed a novel wide-field (>70°) optical coherence tomography system (WF-OCT) equipped with wavefront sensorless adaptive optics (WSAO) for enhancing the visualization of smaller (<25°) targeted regions in the peripheral retina. We iterated the WSAO algorithm at the speed of individual OCT B-scans (~20 ms) by using raw spectral interferograms to calculate the optimization metric...
January 1, 2017: Biomedical Optics Express
Yasushi Inoue, Shintarou Ochi
PURPOSE: To evaluate the effects of diquafosol sodium ophthalmic solution 3% (DQS) and artificial tears (AT) on higher-order aberrations (HOAs) in patients with dry eye after cataract surgery. DESIGN: This was a post hoc analysis of a previously conducted randomized clinical study. METHODS: Fifty-nine eyes from 42 patients (17 males and 25 females, aged 72.6±8.0 years) with verified or suspected dry eye at 4 weeks after cataract surgery were evaluated...
2017: Clinical Ophthalmology
Jérome Chal, Charlène Guillot, Olivier Pourquié
Vertebrate segmentation is characterized by the periodic formation of epithelial somites from the mesenchymal presomitic mesoderm (PSM). How the rhythmic signaling pulse delivered by the Segmentation Clock is translated into the periodic morphogenesis of somites remains poorly understood. Here, we focused on the role of Paraxial protocadherin (PAPC/Pcdh8) in this process. We showed that in chicken and mouse embryos, PAPC expression is tightly regulated by the Clock and Wavefront system in the posterior PSM...
January 13, 2017: Development
Motohiro Banno, Konosuke Onda, Hiroharu Yui
The development of a stimulated Raman scattering (SRS) microscope with a wavefront modulation unit is presented. In the apparatus, two beams for introducing the SRS process were focused into the sample with an objective lens. In the pathway of the Stokes beam, which is one of the two incident beams, a spatial light modulator (SLM) was located. Using the SLM, the wavefront of the Stokes beam was modulated to make the shape of the focal point a concentric circular pattern. By this spot shaping technique, the area where the SRS signal generates is restricted...
2017: Analytical Sciences: the International Journal of the Japan Society for Analytical Chemistry
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