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Strehl ratio

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https://www.readbyqxmd.com/read/28433446/functional-magnetic-resonance-imaging-to-assess-the-neurobehavioral-impact-of-dysphotopsia-with-multifocal-intraocular-lenses
#1
Andreia M Rosa, Ângela C Miranda, Miguel Patrício, Colm McAlinden, Fátima L Silva, Joaquim N Murta, Miguel Castelo-Branco
PURPOSE: To investigate the association between dysphotopsia and neural responses in visual and higher-level cortical regions in patients who recently received multifocal intraocular lens (IOL) implants. DESIGN: Cross-sectional study. PARTICIPANTS: Thirty patients 3 to 4 weeks after bilateral cataract surgery with diffractive IOL implantation and 15 age- and gender-matched control subjects. METHODS: Functional magnetic resonance imaging (fMRI) was performed when participants viewed low-contrast grating stimuli...
April 19, 2017: Ophthalmology
https://www.readbyqxmd.com/read/28388086/immersion-meta-lenses-at-visible-wavelengths-for-nanoscale-imaging
#2
Wei Ting Chen, Alexander Yutong Zhu, Mohammadreza Khorasaninejad, Zhujun Shi, Vyshakh Sanjeev, Federico Capasso
Immersion objectives can focus light into a spot smaller than what is achievable in free space, thereby enhancing the spatial resolution for various applications such as microscopy, spectroscopy, and lithography. Despite the availability of advanced lens polishing techniques, hand-polishing is still required to manufacture the front lens of an immersion objective, which poses major constraints for lens design. This limits the shape of the front lens to spherical. Therefore, several other lenses need to be cascaded to correct for spherical aberration, resulting in significant challenges for miniaturization and adding design complexity for different immersion liquids...
April 7, 2017: Nano Letters
https://www.readbyqxmd.com/read/28384541/focused-ion-beam-assisted-fabrication-of-soft-high-aspect-ratio-silicon-nanowire-atomic-force-microscopy-probes
#3
Peter Knittel, Nicolas Hibst, Boris Mizaikoff, Steffen Strehle, Christine Kranz
In this study, high-aspect ratio silicon nanowire (SiNW) - modified atomic force microscopy (AFM) probes are fabricated using focused ion beam (FIB) microfabrication technology and vapor-solid-solid synthesis. Commercially available soft silicon nitride probes are used for localized nanowire growth yielding soft high-aspect ratio AFM probes. The SiNW-modified cantilevers are used here for imaging in PeakForce Tappingۛ (PFT) mode, which offers high force control along with valuable information about tip-sample adhesion...
March 28, 2017: Ultramicroscopy
https://www.readbyqxmd.com/read/28380650/-evaluation-of-postoperative-astigmatism-correction-and-postoperative-rotational-stability-of-two-toric-intraocular-lenses
#4
M Grohlich, K Miháltz, M Lasta, B Weingessel, V Vécsei-Marlovits
Background The aim of this retrospective study was to evaluate the rotational stability and the refractive outcome of two different toric IOLs. Methods This study included 41 eyes with corneal astigmatism greater than 1.5 diopters (D). All patients underwent surgery in the Department of Ophthalmology at Hietzing Hospital between 2010 and 2013. The study lenses were the Alcon AcrySof IQ Toric IOL and the Abbott Tecnis Toric Aspheric IOL. Measurements of corneal topography and aberrations were performed with the HOYA iTrace™...
April 5, 2017: Klinische Monatsblätter Für Augenheilkunde
https://www.readbyqxmd.com/read/28379648/cap-lenticular-adhesion-during-small-incision-lenticular-extraction-surgery-causative-factors-and-outcomes
#5
Rohit Shetty, Nikhil Negalur, Rushad Shroff, Kalyani Deshpande, Chaitra Jayadev
PURPOSE: To study the factors causing cap lenticular adhesion (CLA), a rare complication of small incision lenticule extraction (SMILE) surgery, and its effect on surgical outcomes. DESIGN: A prospective, observational, cross-sectional study involving 550 eyes of 285 subjects. METHODS: SMILE was performed using the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) with a minimum of 3 months follow-up. Preoperative visual quality assessment, measurement of corneal biomechanics, and Bowman membrane imaging were performed...
March 29, 2017: Asia-Pacific Journal of Ophthalmology
https://www.readbyqxmd.com/read/28375317/interaction-of-aberrations-diffraction-and-quantal-fluctuations-determine-the-impact-of-pupil-size-on-visual-quality
#6
Renfeng Xu, Huachun Wang, Larry N Thibos, Arthur Bradley
Our purpose is to develop a computational approach that jointly assesses the impact of stimulus luminance and pupil size on visual quality. We compared traditional optical measures of image quality and those that incorporate the impact of retinal illuminance dependent neural contrast sensitivity. Visually weighted image quality was calculated for a presbyopic model eye with representative levels of chromatic and monochromatic aberrations as pupil diameter was varied from 7 to 1 mm, stimulus luminance varied from 2000 to 0...
April 1, 2017: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
https://www.readbyqxmd.com/read/28375280/strehl-ratio-and-amplitude-weighted-generalized-orthonormal-zernike-based-polynomials
#7
Cosmas Mafusire, Tjaart P J Krüger
The concept of orthonormal polynomials is revisited by developing a Zernike-based orthonormal set for a non-circular pupil that is transmitting an aberrated, non-uniform field. We refer to this pupil as a general pupil. The process is achieved by using the matrix form of the Gram-Schmidt procedure on Zernike circle polynomials and is interpreted as a process of balancing each Zernike circle polynomial by adding those of lower order in the general pupil, a procedure which was previously performed using classical aberrations...
March 10, 2017: Applied Optics
https://www.readbyqxmd.com/read/28370389/is-an-objective-refraction-optimised-using-the-visual-strehl-ratio-better-than-a-subjective-refraction
#8
Gareth D Hastings, Jason D Marsack, Lan Chi Nguyen, Han Cheng, Raymond A Applegate
PURPOSE: To prospectively examine whether using the visual image quality metric, visual Strehl (VSX), to optimise objective refraction from wavefront error measurements can provide equivalent or better visual performance than subjective refraction and which refraction is preferred in free viewing. METHODS: Subjective refractions and wavefront aberrations were measured on 40 visually-normal eyes of 20 subjects, through natural and dilated pupils. For each eye a sphere, cylinder, and axis prescription was also objectively determined that optimised visual image quality (VSX) for the measured wavefront error...
March 30, 2017: Ophthalmic & Physiological Optics: the Journal of the British College of Ophthalmic Opticians (Optometrists)
https://www.readbyqxmd.com/read/28346278/effects-of-myopic-orthokeratology-on-visual-performance-and-optical-quality
#9
Guihua Liu, Zhi Chen, Feng Xue, Jing Li, Mi Tian, Xingtao Zhou, Ruihua Wei
OBJECTIVES: To analyze the changes in visual performance and optical quality after orthokeratology (ortho-k) treatment and its correlation with the magnitude of lens decentration and the diameter of treatment zone (TxZ). METHODS: A prospective study was conducted in 27 eyes of 27 patients wearing ortho-k contact lens. Area under log contrast sensitivity function (AULCSF), modulation transfer function cutoff values (MTFcutoff), Strehl ratio (SR), and objective scattering index (OSI) were measured and compared before and 1 month after ortho-k lens treatment...
March 24, 2017: Eye & Contact Lens
https://www.readbyqxmd.com/read/28248317/perfect-x-ray-focusing-via-fitting-corrective-glasses-to-aberrated-optics
#10
Frank Seiboth, Andreas Schropp, Maria Scholz, Felix Wittwer, Christian Rödel, Martin Wünsche, Tobias Ullsperger, Stefan Nolte, Jussi Rahomäki, Karolis Parfeniukas, Stylianos Giakoumidis, Ulrich Vogt, Ulrich Wagner, Christoph Rau, Ulrike Boesenberg, Jan Garrevoet, Gerald Falkenberg, Eric C Galtier, Hae Ja Lee, Bob Nagler, Christian G Schroer
Due to their short wavelength, X-rays can in principle be focused down to a few nanometres and below. At the same time, it is this short wavelength that puts stringent requirements on X-ray optics and their metrology. Both are limited by today's technology. In this work, we present accurate at wavelength measurements of residual aberrations of a refractive X-ray lens using ptychography to manufacture a corrective phase plate. Together with the fitted phase plate the optics shows diffraction-limited performance, generating a nearly Gaussian beam profile with a Strehl ratio above 0...
March 1, 2017: Nature Communications
https://www.readbyqxmd.com/read/28211182/accommodation-and-pupil-behaviour-of-binocularly-viewing-early-presbyopes
#11
Meznah S Almutairi, Basal H Altoaimi, Arthur Bradley
PURPOSE: To study accommodation behaviour of early presbyopes with the full suite of accommodative stimuli, and to monitor changes in spherical aberration, pupil size and image quality that accompany the accommodative response. METHODS: Using a high resolution Shack-Hartmann aberrometer, we measured refractive state as a binocularly viewed 0.30 logMAR (6/12 or 20/40) letter E was moved from 2 m to 20 cm and simultaneously monitored pupil diameter and spherical aberration for 19 subjects (mean age: 42 ± 7...
March 2017: Ophthalmic & Physiological Optics: the Journal of the British College of Ophthalmic Opticians (Optometrists)
https://www.readbyqxmd.com/read/28178942/in-vitro-comparative-optical-bench-analysis-of-a-spherical-and-aspheric-optic-design-of-the-same-iol-model
#12
Tamer Tandogan, Gerd U Auffarth, Chul Y Choi, Stephanie Liebing, Christian Mayer, Ramin Khoramnia
BACKGROUND: To analyse objective optical properties of the spherical and aspheric design of the same intraocular lens (IOL) model using optical bench analysis. METHODS: This study entailed a comparative analysis of 10 spherical C-flex 570 C and 10 aspheric C-flex 970 C IOLs (Rayner Intraocular Lenses Ltd., Hove, UK) of 26 diopters [D] using an optical bench (OptiSpheric, Trioptics, Germany). In all lenses, we evaluated the modulation transfer function (MTF) at 50 lp/mm and 100 lp/mm and the Strehl Ratio using a 3-mm (photopic) and 4...
February 8, 2017: BMC Ophthalmology
https://www.readbyqxmd.com/read/28152553/the-effect-of-aberrations-on-objectively-assessed-image-quality-and-depth-of-focus
#13
Antonio J Del Águila-Carrasco, Scott A Read, Robert Montés-Micó, D Robert Iskander
The effects of aberrations on image quality and the objectively assessed depth of focus (DoF) were studied. Aberrometry data from 80 young subjects with a range of refractive errors was used for computing the visual Strehl ratio based on the optical transfer function (VSOTF), and then, through-focus simulations were performed in order to calculate the objective DoF (using two different relative thresholds of 50% and 80%; and two different pupil diameters) and the image quality (the peak VSOTF). Both lower order astigmatism and higher order aberration (HOA) terms up to the fifth radial order were considered...
February 1, 2017: Journal of Vision
https://www.readbyqxmd.com/read/28150357/prevalence-and-correlates-of-somatoform-disorders-in-the-elderly-results-of-a-european-study
#14
Maria Christina Dehoust, Holger Schulz, Martin Härter, Jana Volkert, Susanne Sehner, Anna Drabik, Karl Wegscheider, Alessandra Canuto, Kerstin Weber, Mike Crawford, Alan Quirk, Luigi Grassi, Chiara DaRonch, Manuel Munoz, Berta Ausin, Anna Santos-Olmo, Arieh Shalev, Ora Rotenstein, Yael Hershkowitz, Jens Strehle, Hans-Ulrich Wittchen, Sylke Andreas
Somatoform disorders have rarely been addressed in epidemiological and health care services studies of the elderly. The few existing studies vary considerably in their methodologies limiting comparability of findings. Data come from the MentDis_ICF65+ study, in which a total of 3142 community-dwelling respondents aged 65-84 years from six different countries were assessed by the Composite International Diagnostic Interview adapted to the needs of the elderly (CIDI65+). The 12-month prevalence rate for any somatoform disorders was found to be 3...
February 1, 2017: International Journal of Methods in Psychiatric Research
https://www.readbyqxmd.com/read/28105741/potential-use-of-cubic-phase-masks-for-extending-the-range-of-clear-vision-in-presbyopes-initial-calculation-and-simulation-studies
#15
Justo Arines, Citlalli Almaguer, Eva Acosta
PURPOSE: In this paper we analyse the potential use of a non-symmetrical optical element, a cubic phase mask, for extending the range of clear vision of presbyopic eyes. Additionally, we will discuss the appropriateness of the visual Strehl ratio to analyse this sort of presbyopic solution based on non-symmetrical phase masks contrasted with through-focus retinal images. METHODS: In order to evaluate the performance of the cubic phase mask we employed computational Fourier Optics to compute the different visual Strehl criteria as well as simulate the retinal images...
January 20, 2017: Ophthalmic & Physiological Optics: the Journal of the British College of Ophthalmic Opticians (Optometrists)
https://www.readbyqxmd.com/read/27958424/spectral-phase-effects-and-control-requirements-of-coherent-beam-combining-for-ultrashort-ultrahigh-intensity-laser-systems
#16
Yong Cui, Yan-Qi Gao, Ze-Xi Zhao, Zhong-Yang Xu, Ning An, Da-Wei Li, Jian-Wei Yu, Tao Wang, Guang Xu, Wei-Xin Ma, Ya-Ping Dai
Based on the premise that further improvements to the size and damage threshold of large-aperture optical components are severely limited, coherent beam combining (CBC) is a promising way to scale up the available peak power of pulses for ultrashort ultrahigh intensity laser systems. Spectral phase effects are important issues and have a significant impact on the performance of CBC. In this work, we analyze systematically factors such as spectral dispersions and longitudinal chromatism, and get the general spectral phase control requirements of CBC for ultrashort ultrahigh intensity laser systems...
December 10, 2016: Applied Optics
https://www.readbyqxmd.com/read/27958406/single-acquisition-wide-field-superresolution-for-telescopes
#17
Steve Wereley, Yuxing Zhang, Jian-Wei Khor, Craig Snoeyink
A simple optical setup is introduced here that is capable of improving the diffraction-limited angular resolution of a telescope at minimal cost to image quality. The system consists of, at minimum, an axicon and a convex lens located in the optical path of the telescope, which can increase the angular resolution by up to 38%. Analytical results for this resolution gain along with the Strehl ratio of this system are presented along with experimental results, which show a 30% improvement in single-acquisition image resolution with a Strehl ratio of 0...
December 10, 2016: Applied Optics
https://www.readbyqxmd.com/read/27895981/perceived-image-quality-with-simulated-segmented-bifocal-corrections
#18
Carlos Dorronsoro, Aiswaryah Radhakrishnan, Pablo de Gracia, Lucie Sawides, Susana Marcos
Bifocal contact or intraocular lenses use the principle of simultaneous vision to correct for presbyopia. A modified two-channel simultaneous vision simulator provided with an amplitude transmission spatial light modulator was used to optically simulate 14 segmented bifocal patterns (+ 3 diopters addition) with different far/near pupillary distributions of equal energy. Five subjects with paralyzed accommodation evaluated image quality and subjective preference through the segmented bifocal corrections. There are strong and systematic perceptual differences across the patterns, subjects and observation distances: 48% of the conditions evaluated were significantly preferred or rejected...
November 1, 2016: Biomedical Optics Express
https://www.readbyqxmd.com/read/27828088/virtual-pyramid-wavefront-sensor-for-phase-unwrapping
#19
Vyas Akondi, Brian Vohnsen, Susana Marcos
Noise affects wavefront reconstruction from wrapped phase data. A novel method of phase unwrapping is proposed with the help of a virtual pyramid wavefront sensor. The method was tested on noisy wrapped phase images obtained experimentally with a digital phase-shifting point diffraction interferometer. The virtuality of the pyramid wavefront sensor allows easy tuning of the pyramid apex angle and modulation amplitude. It is shown that an optimal modulation amplitude obtained by monitoring the Strehl ratio helps in achieving better accuracy...
October 10, 2016: Applied Optics
https://www.readbyqxmd.com/read/27791380/polarization-insensitive-metalenses-at-visible-wavelengths
#20
M Khorasaninejad, A Y Zhu, C Roques-Carmes, W T Chen, J Oh, I Mishra, R C Devlin, F Capasso
In this Letter, we demonstrate highly efficient, polarization-insensitive planar lenses (metalenses) at red, green, and blue wavelengths (λ = 660, 532, and 405 nm). Metalenses with numerical apertures (NA) of 0.85 and 0.6 and corresponding efficiencies as high as 60% and 90% are achieved. These metalenses are less than 600 nm-thick and can focus incident light down to diffraction-limited spots as small as ∼0.64λ and provide high-resolution imaging. In addition, the focal spots are very symmetric with high Strehl ratios...
November 9, 2016: Nano Letters
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