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https://www.readbyqxmd.com/read/29047974/mean-estimation-empirical-mode-decomposition-method-for-terahertz-time-domain-spectroscopy-de-noising
#1
Xiaoli Qiao, Xinming Zhang, Jiaojiao Ren, Dandan Zhang, Guohua Cao, Lijuan Li
The wavelet-domain de-noising technique has many applications in terahertz time-domain spectroscopy (THz-TDS). However, it requires a complex procedure for the selection of the optimal wavelet basis and threshold, which varies for different materials. Inappropriate selections can lead to de-noising failure. Here, we propose the Mean Estimation Empirical Mode Decomposition (ME-EMD) de-noising method for THz-TDS. First, the THz-TDS signal and the collected reference noise are decomposed into the intrinsic mode functions (IMFs); second, the maximum and mean absolute values of the noise IMF amplitudes are calculated and defined as the adaptive threshold and adaptive estimated noise value, respectively; finally, these thresholds and estimated noise values are utilized to filter the noise from the signal IMFs and reconstruct the THz-TDS signal...
September 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/29047766/measurement-of-refractive-index-profiles-in-optical-waveguides-by-moir%C3%A3-deflectometry-technique
#2
Mohammad Ahmadi, Khosro Madanipour, Soheila Javadianvarjovi
Measurement of refractive index profiles in optical waveguides is an important issue for controlling manufacturing procedures and determination of some important characteristics of waveguides. In this paper, an optical waveguide is considered as a phase object. When collimated laser beams are illuminated on waveguides, the refractive index gradient distorts the plane waves, then the distortion is determined by use of the moiré deflectometry method. Dimensions of the waveguides under study are on the order of 10 μm, so the moiré deflectometry setup was changed and optimized for measuring in the micrometer dimensions...
October 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/29042748/corneal-biomechanical-properties-after-laser-assisted-in-situ-keratomileusis-and-photorefractive-keratectomy
#3
Eileen S Hwang, Brian C Stagg, Russell Swan, Carlton R Fenzl, Molly McFadden, Valliammai Muthappan, Luis Santiago-Caban, Mark D Mifflin, Majid Moshirfar
BACKGROUND: The purpose of this study was to evaluate the effects of laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) on corneal biomechanical properties. METHODS: We used the ocular response analyzer to measure corneal hysteresis (CH) and corneal resistance factor (CRF) before and after refractive surgery. RESULTS: In all, 230 eyes underwent LASIK and 115 eyes underwent PRK without mitomycin C (MMC). Both procedures decreased CH and CRF from baseline...
2017: Clinical Ophthalmology
https://www.readbyqxmd.com/read/29036140/wavefronts-caustic-and-intensity-of-a-plane-wave-refracted-by-an-arbitrary-surface-the-axicon-and-the-plano-spherical-lenses
#4
Paula Ortega-Vidals, Omar de Jesús Cabrera-Rosas, Ernesto Espíndola Ramos, Salvador Alejandro Juárez Reyes, Israel Julían Macías, Gilberto Silva-Ortigoza, Ramón Silva-Ortigoza, Citlalli Teresa Sosa-Sánchez
The aim of the present work is to obtain an integral representation of the field associated with the refraction of a plane wave by an arbitrary surface. To this end, in the first part we consider two optical media with refraction indexes n1 and n2 separated by an arbitrary interface, and we show that the optical path length, ϕ, associated with the evolution of the plane wave is a complete integral of the eikonal equation in the optical medium with refraction index n2. Then by using the k function procedure introduced by Stavroudis, we define a new complete integral, S, of the eikonal equation...
September 1, 2017: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
https://www.readbyqxmd.com/read/29034156/intraocular-lens-opacification-after-descemet-s-stripping-automated-endothelial-keratoplasty
#5
Meng-Sheng Lee, I-Lun Tsai, Ching-Yao Tsai, Li-Lin Kuo, Shiow-Wen Liou, Lin-Chung Woung
Compared with conventional penetrating keratoplasty, Descemet's stripping automated endothelial keratoplasty (DSAEK) more effectively maintain global integrity and rapid vision rehabilitation with less ocular surface disorders in patients with endothelial dysfunction. Here, we report a case of a 76-year-old woman who experienced opacification of a hydrophilic intraocular lens (IOL) approximately 10 months after DSAEK. The patient with no history of systemic disease developed pseudophakic bullous keratopathy in the right eye 2 years after undergoing cataract surgery...
July 2017: Taiwan Journal of Ophthalmology
https://www.readbyqxmd.com/read/28991621/central-island-formation-after-cataract-surgery-in-a-laser-in%C3%A2-situ-keratomileusis-eye-new-etiology
#6
Sylvain El-Khoury, Youssef Abdelmassih, George Cherfan, Johnny M Khoury
We report a case of central corneal steepness formation after cataract surgery in a post-laser in situ keratomileusis (LASIK) eye. A 51-year-old woman with traumatic cataract and a history of myopic LASIK surgery had uneventful phacoemulsification cataract surgery. Postoperatively, the corneal topography difference map showed a central island formation of 2.1 diopters (D) compared with the preoperative level, which correlated with a clinical myopic shift of 2.00 D from the targeted emmetropia. At 4 months, most of the central island had resolved spontaneously...
September 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/28991616/refractive-lens-exchange-and-piggyback-intraocular-lens-implantation-in-nanophthalmos-visual-and-structural-outcomes
#7
Masoomeh Mohebbi, Mohammad-Reza Fallah-Tafti, Kaveh Fadakar, Ramon Katoozpour, Seyed-Farzad Mohammadi, Zahra Fallah-Tafti, Azita Khorami
PURPOSE: To evaluate the best piggyback intraocular lens (IOL) implantation method and the outcomes in nanophthalmos eyes and to define the postoperative structural changes. SETTING: Farabi Eye Hospital, Tehran, Iran. DESIGN: Prospective case series. METHODS: Candidates for refractive surgery who were nanophthalmic were recruited. Patients had refractive lens exchange followed by implantation of both IOLs in the bag or 1 IOL in the bag and 1 IOL in the sulcus...
September 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/28991336/four-stage-procedure-for-keratoconus-icrs-implantation-corneal-cross-linking-toric-phakic-intraocular-lens-implantation-and-topography-guided-photorefractive-keratectomy
#8
Efekan Coskunseven, Daya Papalkar Sharma, Michael A Grentzelos, Onurcan Sahin, George D Kymionis, Ioannis Pallikaris
PURPOSE: To evaluate a four-stage combined treatment for keratoconus including intrastromal corneal ring segment (ICRS) implantation followed by corneal cross-linking (CXL), toric phakic intraocular lens (IOL) implantation, and topography-guided photorefractive keratectomy (TG-PRK). METHODS: In this retrospective interventional case series, 11 eyes of 7 patients with progressive keratoconus were treated with a four-stage procedure including the following: Keraring ICRS (Mediphacos Ltda, Belo Horizonte, Brazil) implantation followed by CXL, phakic IOL implantation, and TG-PRK (minimum 6 months between each stage)...
October 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/28953492/descemet-membrane-endothelial-keratoplasty-in-eyes-with-previous-laser-refractive-surgery-outcomes-and-complications
#9
Dorian A Zeidenweber, Zachary M Mayko, Michael D Straiko, Mark A Terry
PURPOSE: To evaluate the refractive predictability and efficacy of Descemet membrane endothelial keratoplasty (DMEK) for patients with previous laser refractive surgery. METHODS: We retrospectively reviewed our cohort of endothelial keratoplasty surgical cases. We identified 21 eyes that underwent laser-assisted in situ keratomileusis (n = 17) or photorefractive keratectomy (n = 4) and were treated with DMEK for endothelial failure. Patients were analyzed preoperatively and at 6 months postoperatively for changes in visual acuity, refraction, and corneal topography...
September 27, 2017: Cornea
https://www.readbyqxmd.com/read/28948045/long-term-follow-up-of-intrastromal-corneal-ring-segments-in-paracentral-keratoconus-with-coincident-corneal-keratometric-comatic-and-refractive-axes-stability-of-the-procedure
#10
Luis Fernández-Vega Cueto, Carlos Lisa, David Madrid-Costa, Jesús Merayo-Lloves, José F Alfonso
PURPOSE: To assess the long-term outcomes of implanting intrastromal corneal ring segments (ICRS) in paracentral keratoconic eyes. METHODS: 58 eyes with paracentral keratoconus with coincident refractive, keratometric, and comatic axes were evaluated. Uncorrected (UDVA) and corrected (CDVA) distance visual acuity and refractive errors were recorded before and at all follow-up visits. The postoperative follow-up was 5 years. Patients were divided into two groups: group I (30 years old or younger) and group II (more than 30 years old)...
2017: Journal of Ophthalmology
https://www.readbyqxmd.com/read/28932334/corneal-biomechanics-in-ectatic-diseases-refractive-surgery-implications
#11
Renato Ambrósio, Fernando Faria Correia, Bernardo Lopes, Marcella Q Salomão, Allan Luz, Daniel G Dawson, Ahmed Elsheikh, Riccardo Vinciguerra, Paolo Vinciguerra, Cynthia J Roberts
BACKGROUND: Ectasia development occurs due to a chronic corneal biomechanical decompensation or weakness, resulting in stromal thinning and corneal protrusion. This leads to corneal steepening, increase in astigmatism, and irregularity. In corneal refractive surgery, the detection of mild forms of ectasia pre-operatively is essential to avoid post-operative progressive ectasia, which also depends on the impact of the procedure on the cornea. METHOD: The advent of 3D tomography is proven as a significant advancement to further characterize corneal shape beyond front surface topography, which is still relevant...
2017: Open Ophthalmology Journal
https://www.readbyqxmd.com/read/28931181/-refractive-lens-exchange
#12
Fritz H Hengerer, Ina Conrad-Hengerer
In refractive surgery the removal of the natural lens followed by implantation of an artificial intraocular lens has been an established method to treat refractive errors. The term "clear lens exchange" separates this approach from cataract surgery, where a cloudy lens has to be removed. With regard to currently available intraocular lens technologies, there is a wide range to correct myopia, hyperopia as well as astigmatism. Trifocal or extended depth-of-focus lenses (EDOF) even with a toric component offer the patients a potential benefit to further address presbyopia, respectively...
October 2017: Klinische Monatsblätter Für Augenheilkunde
https://www.readbyqxmd.com/read/28923587/visual-performance-of-a-quadrifocal-trifocal-intraocular-lens-following-removal-of-the-crystalline-lens
#13
Thomas Kohnen, Michael Herzog, Eva Hemkeppler, Sabrina Schönbrunn, Nina De Lorenzo, Kerstin Petermann, Myriam Böhm
PURPOSE: To evaluate visual performance after implantation of a quadrifocal intraocular lens (IOL). DESIGN: Prospective, non-comparative case series METHODS: Setting: Department of Ophthalmology, Goethe University, Frankfurt, Germany. Patient or Study Population: Twenty-seven patients (54 eyes) received bilateral implantation of the PanOptix IOL (AcrySof® IQ PanOptixTM, Alcon Research, Fort Worth, TX, USA) pre-enrollment. Exclusion criteria were previous ocular surgeries, corneal astigmatism of >1...
September 15, 2017: American Journal of Ophthalmology
https://www.readbyqxmd.com/read/28920158/comparison-of-outcomes-of-scleral-fixation-with-and-without-pars-plana-vitrectomy-for-the-treatment-of-dislocated-intraocular-lens
#14
Seung Yong Choi, You Sook Hwang, Mirinae Kim, Soon Il Choi, Young-Hoon Park
PURPOSE: To investigate the surgical outcomes of scleral fixation with either pars plana vitrectomy (ppV) or anterior vitrectomy (AV) for the treatment of dislocated intraocular lens (IOL). METHODS: By retrospective review of electronic medical records, patients with in-the-bag spontaneous IOL dislocation who underwent IOL exchange with scleral fixation were included and grouped according to the vitrectomy method: ppV (group 1) and AV (group 2). Post-operative surgical outcomes including visual acuity (log MAR), spherical equivalent, and surgically induced astigmatism (SIA) and complications were investigated and analyzed...
September 17, 2017: Graefe's Archive for Clinical and Experimental Ophthalmology
https://www.readbyqxmd.com/read/28905822/higher-order-aberration-4-years-after-corneal-collagen-cross-linking
#15
Mohammad Naderan, Ali Jahanrad
PURPOSE: Corneal collagen cross-linking (CXL) is a treatment strategy used in keratoconic eyes. Evaluation of long-term changes of higher-order aberrations (HOAs) after CXL is useful in understanding the efficacy of this procedure in improving optical, refractive, and visual acuity. This study aims to investigate the long-term effect of CXL on ocular HOA in patients with progressive keratoconus (KC). METHODS: Using an OPD-Scan II aberrometer, ocular HOAs measurements of 56 eyes of 56 patients that underwent CXL was evaluated at the baseline, 1, 2, and 4 years after the procedure...
September 2017: Indian Journal of Ophthalmology
https://www.readbyqxmd.com/read/28880337/effect-of-lowering-laser-energy-on-the-surface-roughness-of-human-corneal-lenticules-in-smile
#16
Yong Woo Ji, Minseo Kim, David Sung Yong Kang, Dan Z Reinstein, Timothy J Archer, Jin Young Choi, Eung Kweon Kim, Hyung Keun Lee, Kyoung Yul Seo, Tae-Im Kim
PURPOSE: To determine the effect of lowering femtosecond laser energy on the surface quality of the intrastromal interface during small incision lenticule extraction (SMILE). METHODS: Forty age- and diopter-matched female patients (40 eyes) with moderate myopia received SMILE with different energy levels (100 to 150 nJ) and fixed spot separation (4.5 μm). Five human corneal lenticules from each energy group were evaluated by atomic force microscopy and scanning electron microscopy (SEM)...
September 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/28880336/toric-icl-implantation-after-sequential-intracorneal-ring-segments-implantation-and-corneal-cross-linking-in-keratoconus-2-year-follow-up
#17
Youssef Abdelmassih, Sylvain El-Khoury, Elias Chelala, Elise Slim, Carole G Cherfan, Elias Jarade
PURPOSE: To evaluate 6-month and 2-year safety and clinical outcomes of Visian toric Implantable Collamer Lens (toric ICL) (STAAR Surgical, Monrovia, CA) implantation for the treatment of residual refractive errors after sequential intracorneal ring segments (ICRS) insertion and cross-linking (CXL) in keratoconus. METHODS: This consecutive case series included the results of a three-step ICRS-CXL-toric ICL procedure in 16 eyes of 13 patients with moderate to severe keratoconus (stages II and III of Amsler-Krumeich classification)...
September 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/28880333/predicting-refractive-surgery-outcome-machine-learning-approach-with-big-data
#18
Asaf Achiron, Zvi Gur, Uri Aviv, Assaf Hilely, Michael Mimouni, Lily Karmona, Lior Rokach, Igor Kaiserman
PURPOSE: To develop a decision forest for prediction of laser refractive surgery outcome. METHODS: Data from consecutive cases of patients who underwent LASIK or photorefractive surgeries during a 12-year period in a single center were assembled into a single dataset. Training of machine-learning classifiers and testing were performed with a statistical classifier algorithm. The decision forest was created by feature vectors extracted from 17,592 cases and 38 clinical parameters for each patient...
September 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/28867856/physicochemical-screening-and-shelf-life-evaluation-of-ku%C3%A1-kum%C3%A4-di-gh%C3%A1-ta-prepared-using-kesara-and-n%C3%A4-gakesara
#19
Pradeep Kumar Prajapati, Rohit Sharma, Amee Amrutia, B J Patgiri
INTRODUCTION: Kuṅkumādi Ghṛta (KG) is an Ayurvedic formulation commonly recommended in skin disorders, especially Mukhadūṣikā (Acne vulgaris). Kesara (stigma of Crocus sativus Linn.) is a prime ingredient in the formulation. However, due to high cost and increased adulteration in Kesara, 'Nāgakesara' (Mesua ferrea Linn.) is suggested by Ayurvedic experts as a substitute. Nāgakesara is relatively lower in cost and possesses similar therapeutic attributes to that of Kesara. Recent studies have established standard manufacturing procedures and clinical efficacies of Kesarayukta (with Kesara) Kuṅkumādi Ghṛta (KKG) and Nāgakesara yukta (with Nāgakesara) Kuṅkumādi Ghṛta (NKG) in Mukhadūṣikā...
January 2017: Ancient Science of Life
https://www.readbyqxmd.com/read/28863711/measurement-of-contact-angles-of-microscopic-droplets-by-focal-length-method
#20
Daniel Geiger, Kirsten Geiger, Tobias Neckernuss, Othmar Marti, Masoud Amirkhani
We present a method to measure contact angles of microscopic droplets with a conventional microscope that possesses a precision focus adjustment stage. The droplets are modeled as spherical caps that act as lenses. Their focal length is determined by measuring the distance from the substrate surface to the level where a sharp image of the aperture stop is observed. The lens diameter is found by edge detection of a microscope image of the microdroplets. The spherical cap model relates the focal length and diameter of such lenses to the contact angle of the used liquid with known refractive index...
August 2017: Review of Scientific Instruments
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