Search results for "Eye"
showing 10 items of 2511 documents
Plasmalogens in the retina: From occurrence in retinal cell membranes to potential involvement in pathophysiology of retinal diseases
2014
Plasmalogens (Pls) represent a specific subclass of glycerophospholipids characterized by the presence of a vinyl-ether bond at the sn-1 position of glycerol. Pls are quantitatively important in membranes of neuronal tissues, including the brain and the retina, where they can represent until almost two-third of ethanolamine glycerophospholipids. They are considered as reservoirs of polyunsaturated fatty acids as several studies have shown that arachidonic and docosahexaenoic acids are preferentially esterified on Pls when compared to other glycerophospholipids. Reduced levels of Pls were observed in a number of neurodegenerative disorders such as glaucoma, the second leading cause of blindn…
Color difference threshold of chromostereopsis induced by flat display emission
2015
The study of chromostereopsis has gained attention in the backdrop of the use of computer displays in daily life. In this context, we analyze the illusory depth sense using planar color images presented on a computer screen. We determine the color difference threshold required to induce an illusory sense of depth psychometrically using a constant stimuli paradigm. Isoluminant stimuli are presented on a computer screen, which stimuli are aligned along the blue–red line in the computer display CIE xyY color space. Stereo disparity is generated by increasing the color difference between the central and surrounding areas of the stimuli with both areas consisting of random dots on a black backgr…
Diffractive corneal inlay for presbyopia
2017
[EN] A conceptually new type of corneal inlays for a customized treatment of presbyopia is presented. The diffractive inlay consists on a small aperture disc having an array of micro-holes distributed inside the open zones of a Fresnel zone plate. In this way, the central hole of the disc lets pass the zero order diffraction and produces an extension of the depth of far focus of the eye, while the diffracted light through the holes in the periphery produce the near focus. Additionally, the micro-holes in the inlay surface fulfill the essential requirement of allowing the flow of nutrients through it to the cells of the corneal stroma. Theoretical and optical-bench experimental results for t…
Clinical use of the ocular point spread function for retinal image quality assessment
2008
The purpose of this study is to demonstrate the clinical use of the point spread function (PSF) as metric for the assessment of retinal image quality in eyes with different ocular conditions. The PSF was computed from the wavefront aberrations obtained in seven eyes with different ocular conditions: emmetropia, myopia, hyperopia, post-myopic laser in situ keratomileusis (LASIK), post-hyperopic LASIK, keratoconus, Intacs ® in keratoconus, radial keratotomy (RK), LASIK after RK, cataract, phacoemulsification after cataract surgery, and LASIK after astigmatic keratotomy. The Strehl intensity ratio was calculated for all the PSFs computed. The PSF was correlated with the change in the optical e…
Simple demonstration of the impact of spherical aberration on optical imaging
2008
We present an experiment, well adapted for students of introductory optics courses, for the visualization of the impact of spherical aberration in the point spread function of imaging systems. The demonstrations are based on the analogy between the point-spread function of spherically aberrated systems, and the defocused patterns of 1D slit-like screens.
Laboratory Studies of Scattering Properties of Polluted Cloud Droplets: Implications for FSSP Measurements
2008
Abstract Laboratory experiments were conducted in the Mainz vertical wind tunnel to study the effects of pollutants dissolved or suspended in cloud droplets on the droplet size measurements of a Forward Scattering Spectrometer Probe (FSSP). The FSSP is a widely used instrument to derive microphysical properties of atmospheric clouds. Individual droplets of different well-defined sizes were freely falling at their terminal velocities in the wind tunnel while the intensity of radiation emitted by the He–Ne laser of the FSSP and scattered by the droplets was measured. For this purpose, the FSSP was adapted and mounted to the wind tunnel. The intensity of radiation scattered by the droplets in …
Dažāda veida mākslīgo asaru ietekme uz sausās acs radītajām pazīmēm un simptomiem
2021
Maģistra darbs ir uzrakstīts angļu valodā uz 5 5 lappaspusēm. Tas satur 13 attēlus, 19 tabulas un 30 atsauces uz literatūras avotiem. Šī pētījuma mērķis ir novērtēt dažādu mākslīgo asaru ietekmi uz sausu acu simptomiem un pazīmēm. Sauso acu slimība (DED) ir hroniska, daudzfaktoru acu virsmas slimība, kas noved pie diskomforta, redzes traucējumiem un asaru plēvītes nestabilitātes, ar iespējamu acu virsmas bojājumu. Vecums un dzimums tiek mi nēts par svarīgākajiem faktoriem, kas izraisa sauso acu slimību, turpretī citi riski bieži netiek ņemti vērā. Lai nozīmētu DED ārstēšanu, jāveic dažādi diagnostikas testi. Mūsdienās ir pieejamas atšķirīgas ārstēšanas metodes, bet mākslīgās asaras ir visbi…
Introduzione ad Arte : Artworks, mimesis, agency
2021
Il volume raccoglie alcune delle relazioni tenute all’interno del ciclo di seminari Antropologia dell’arte, organizzato nel 2019 dall’Associazione per la conservazione delle tradizioni popolari in collaborazione con l’Accademia di Belle Arti di Palermo e curato da Rosario Perricone. Il seminario comprendeva diversi incontri durante i quali studiosi di diversi ambiti disciplinari hanno dibattuto su concetti, nozioni e oggetti che si pongono al crocevia tra le discipline dell’antropologia, della storia dell’arte, della semiotica, degli studi culturali, della visual culture, delineando talvolta fenomeni di ibridazione delle pratiche artistiche ed etnografiche e, talvolta, di dissolvenza delle …
Etnografie ad arte : agency, mimesis, creatività e pratica degli artworks
2021
Il volume raccoglie alcune delle relazioni tenute all’interno del ciclo di seminari Antropologia dell’arte, organizzato nel 2019 dall’Associazione per la conservazione delle tradizioni popolari in collaborazione con l’Accademia di Belle Arti di Palermo e curato da Rosario Perricone. Il seminario comprendeva diversi incontri durante i quali studiosi di diversi ambiti disciplinari hanno dibattuto su concetti, nozioni e oggetti che si pongono al crocevia tra le discipline dell’antropologia, della storia dell’arte, della semiotica, degli studi culturali, della visual culture, delineando talvolta fenomeni di ibridazione delle pratiche artistiche ed etnografiche e, talvolta, di dissolvenza delle …
Pore formation by Vibrio cholerae cytolysin requires cholesterol in both monolayers of the target membrane
2007
Vibrio cholerae cytolysin (VCC) forms oligomeric transmembrane pores in cholesterol-rich membranes. To better understand this process, we used planar bilayer membranes. In symmetric membranes, the rate of the channel formation by VCC has a superlinear dependency on the cholesterol membrane fraction. Thus, more than one cholesterol molecule can facilitate VCC-pore formation. In asymmetric membranes, the rate of pore formation is limited by the leaflet with the lower cholesterol content. Methyl-beta-cyclodextrin, which removes cholesterol from membranes, rapidly inhibits VCC pore formation, even when it is added to the side opposite that of VCC addition. The results suggest that cholesterol i…