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https://www.readbyqxmd.com/read/28717577/temporal-multiplexing-to-simulate-multifocal-intraocular-lenses-theoretical-considerations
#1
Vyas Akondi, Carlos Dorronsoro, Enrique Gambra, Susana Marcos
Fast tunable lenses allow an effective design of a portable simultaneous vision simulator (SimVis) of multifocal corrections. A novel method of evaluating the temporal profile of a tunable lens in simulating different multifocal intraocular lenses (M-IOLs) is presented. The proposed method involves the characteristic fitting of the through-focus (TF) optical quality of the multifocal component of a given M-IOL to a linear combination of TF optical quality of monofocal lenses viable with a tunable lens. Three different types of M-IOL designs are tested, namely: segmented refractive, diffractive and refractive extended depth of focus...
July 1, 2017: Biomedical Optics Express
https://www.readbyqxmd.com/read/28663881/achromatic-doublet-intraocular-lens-for-full-aberration-correction
#2
Enrique J Fernandez, Pablo Artal
A doublet intraocular lens optimized for both chromatic and monochromatic aberration correction in pseudophakic eyes is presented. Ray-tracing techniques were applied to design the lens in white light within a chromatic eye model. Combinations of two materials, already commonly used in intraocular lenses, as acrylic and silicone, were used. Iterative optimization algorithms were employed to correct for longitudinal chromatic aberration, spherical aberration and off-axis aberrations within 10 degrees of visual field...
May 1, 2017: Biomedical Optics Express
https://www.readbyqxmd.com/read/28662629/in-vitro-optical-quality-measurements-of-three-intraocular-lens-models-having-identical-platform
#3
Hyeck Soo Son, Tamer Tandogan, Stephanie Liebing, Patrick Merz, Chul Young Choi, Ramin Khoramnia, Gerd U Auffarth
BACKGROUND: With recent advances in technology and introduction of new intraocular lens (IOL) models, surgeons today have the opportunity to choose from various optical designs, which can influence the postoperative quality of vision. In our laboratory study, we compared the optical quality of three different IOLs that use the identical platform and are produced by the same manufacturer. The study included two diffractive multifocal IOLs, a bifocal and a trifocal one, as well as a monofocal IOL...
June 29, 2017: BMC Ophthalmology
https://www.readbyqxmd.com/read/28538867/preval%C3%A3%C2%AAncia-de-infec%C3%A3-%C3%A3-o-por-helicobacter-pylori-em-uma-comunidade-ind%C3%A3-gena-em-s%C3%A3-o-paulo-e-fatores-associados-estudo-transversalprevalence-of-helicobacter-pylori-infection-in-an-indigenous-community-in-s%C3%A3-o-paulo-and-associated-factors-cross-sectional-study
#4
Juliana Rejane da Silva Roque, Rodrigo Strehl Machado, Douglas Rodrigues, Patrícia Rech, Elisabete Kawakami
CONTEXT AND OBJECTIVE: The prevalence of Helicobacter pylori infection is unevenly distributed among different populations. The aim here was to evaluate the factors associated with Helicobacter pylori infection among children up to five years of age living in a high-risk community. DESIGN AND SETTING: Cross-sectional study in an indigenous community of Guarani Mbya ethnicity, Tekoa Ytu and Tekoa Pyau villages, Jaraguá district, city of São Paulo (SP), Brazil. METHODS: 74 children aged 0...
March 2017: São Paulo Medical Journal, Revista Paulista de Medicina
https://www.readbyqxmd.com/read/28522252/optical-quality-of-rotationally-symmetrical-contact-lenses-derived-from-their-power-profiles
#5
Antonio J Del Águila-Carrasco, Daniel Monsálvez-Romín, Eleni Papadatou
PURPOSE: To present a methodology for evaluating the optical quality of rotationally symmetrical contact lenses (CLs) from a single power profile. METHODS: Simulated rotationally symmetrical power profiles corresponding to different CLs designs (monofocal, two-zone center-near bifocal, and four-zone center-distance bifocal) were used to calculate the wavefront error profile by means of numerical integration. Then, each lens wavefront error profile was spun around the center to obtain the lens wavefront error surface...
May 15, 2017: Contact Lens & Anterior Eye: the Journal of the British Contact Lens Association
https://www.readbyqxmd.com/read/28503437/comparison-of-postoperative-optical-quality-according-to-the-degree-of-decentering-of-v4c-implantable-collamer-lens
#6
Min Ji Park, Hye Min Jeon, Kyoung Heon Lee, Sang Youp Han
AIM: To evaluate the clinical outcomes of V4c implantable collamer lens (Hole ICL) implantation with regard to the optical quality assessed according to different degrees of decentering. METHODS: This included 49 eyes that received conventional ICL and 94 eyes that received Hole ICL. The eyes that received Hole ICL were divided into three groups according to the degree of decentering: group 1, central hole within 1 hole diameter (HD) from the pupil center; group 2, central hole within 1 HD to 2 HD; and group 3, central hole within 2 HD to 3 HD...
2017: International Journal of Ophthalmology
https://www.readbyqxmd.com/read/28469941/intraocular-telescopic-system-design-optical-and-visual-simulation-in-a-human-eye-model
#7
Georgios Zoulinakis, Teresa Ferrer-Blasco
Purpose. To design an intraocular telescopic system (ITS) for magnifying retinal image and to simulate its optical and visual performance after implantation in a human eye model. Methods. Design and simulation were carried out with a ray-tracing and optical design software. Two different ITS were designed, and their visual performance was simulated using the Liou-Brennan eye model. The difference between the ITS was their lenses' placement in the eye model and their powers. Ray tracing in both centered and decentered situations was carried out for both ITS while visual Strehl ratio (VSOTF) was computed using custom-made MATLAB code...
2017: Journal of Ophthalmology
https://www.readbyqxmd.com/read/28433446/functional-magnetic-resonance-imaging-to-assess-the-neurobehavioral-impact-of-dysphotopsia-with-multifocal-intraocular-lenses
#8
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
#9
Wei Ting Chen, Alexander Y 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 a high-end 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 13, 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
#10
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...
August 2017: Ultramicroscopy
https://www.readbyqxmd.com/read/28380650/-evaluation-of-postoperative-astigmatism-correction-and-postoperative-rotational-stability-of-two-toric-intraocular-lenses
#11
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™...
June 2017: Klinische Monatsblätter Für Augenheilkunde
https://www.readbyqxmd.com/read/28379648/cap-lenticular-adhesion-during-small-incision-lenticular-extraction-surgery-causative-factors-and-outcomes
#12
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...
May 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
#13
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
#14
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
#15
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...
May 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
#16
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
#17
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
#18
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
#19
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
#20
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
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