Search results for "Lenses"
showing 10 items of 294 documents
Estimation of the mechanical properties of the eye through the study of its vibrational modes.
2017
Measuring the eye's mechanical properties in vivo and with minimally invasive techniques can be the key for individualized solutions to a number of eye pathologies. The development of such techniques largely relies on a computational modelling of the eyeball and, it optimally requires the synergic interplay between experimentation and numerical simulation. In Astrophysics and Geophysics the remote measurement of structural properties of the systems of their realm is performed on the basis of (helio-)seismic techniques. As a biomechanical system, the eyeball possesses normal vibrational modes encompassing rich information about its structure and mechanical properties. However, the integral a…
Kontaktlēcu ietekme uz redzes asumu pacientiem ar neregulāru radzeni
2017
Darbs uzrakstīts angļu valodā uz 39 lapām. Tas satur 11 attēlus, 1 aptaujas lapu, 11 tabulas and 24 atsauces uz literatūras avotiem. Mērķis: darba galvenais mērķis ir salīdzināt parastās gāzu caurlaidīgās kontaktlēcas ar gāzu caurlaidīgajām intralimbālajām lēcām. Metodes: gāzu caurlaidīgās intralimbālās lēcas tika novērtētas, pētījuma dalībniekiem aizpildot anketu. Rezultāti: pētījuma dalībnieki deva priekšroku gāzu caurlaidīgajām intralimbālajām lēcām un novērtēja to sniegto komfortu, tomēr nebija būtiskas atšķirības starp iegūto redzes asumu abu lēcu gadījumā. Secinājumi: izvērtējot katra pacienta individuālo sutāciju, optometrists var apsvērt intralimbālo lēcu izrakstīšanu pecientam, lai…
Kontaktlēcu pacientu līdzestība un nelīdzestības iemesli Latvijā
2019
Bakalaura darbs ir uzrakstīts latviešu valodā uz 73 lapām. Darbs sastāv no ievada, teorētiskās un praktiskās daļas. Darbs satur 42 attēlus, 6 tabulas, 3 pielikumus un 63 literatūras avotu atsauces. Bakalaura darba mērķis: Novērtēt kontaktlēcu pacientu līdzestības un nelīdzestības iemeslus Latvijā. Bakalaura darba uzdevumi: 1. Ar anketēšanas palīdzību noskaidrot un salīdzināt kontaktlēcu lietotāju un optometristu asistentu zināšanas par kontaktlēcu lietošanu un kopšanu. 2. Noskaidrot kontaktlēcu lietotāju biežākās sūdzības. 3. Novērtēt kontaktlēcu lietotāju līdzestību. Metode: Izveidotas 3 anketas. Kontaktlēcu lietotāju anketa izveidotā divās valodas (latviešu un krievu valodā) un sastāv no …
Generation of programmable 3D optical vortex structures through devil’s vortex-lens arrays
2013
Different spatial distributions of optical vortices have been generated and characterized by implementing arrays of devil's vortex lenses in a reconfigurable spatial light modulator. A simple design procedure assigns the preferred position and topological charge value to each vortex in the structure, tuning the desired angular momentum. Distributions with charges and momenta of the opposite sign have been experimentally demonstrated. The angular velocity exhibited by the phase distribution around the focal plane has been visualized, showing an excellent agreement with the simulations. The practical limits of the method, with interest for applications involving particle transfer and manipula…
Determining postoperative anterior chamber depth
2003
Abstract Purpose: To compare measured and calculated postoperative anterior chamber depths (ACDs). Setting: Department of Ophthalmology and Institute of Medical Physics, University of Vienna, Vienna, Austria, and Department of Ophthalmology, University of Mainz, Mainz, Germany. Methods: The postoperative ACD was measured in 189 pseudophakic eyes using a laboratory prototype of partial coherence interferometry (PCI). In 6 intraocular lens (IOL) groups, the mean ACD was calculated by ray tracing based on the best-known A-constants of the SRK formulas. In addition, for each IOL type, each measured ACD was compared with a value calculated using the individual spherical equivalent of the postope…
Tear Film Surface Quality in Modern Daily Disposable Contact Lens Wear
2021
Objectives As reported previously, tear film surface quality (TFSQ) should be considered in contact lens (CL) fitting. This study followed noninvasive keratograph tear film break-up time (NIKBUT) in CL wearers for 12 months to validate its clinical utility in predicting CL performance. Methods Fifty-five subjects (M/F=17/38) aged 26±4 years were prescribed silicone hydrogel or hydrogel CLs. The study included baseline measurements without CLs; 2 visits for CL fitting and control; follow-up after 3, 6, and 12 months of CL wear; and postwear visit without CLs. Ocular Surface Disease Index (OSDI), 8-Item Contact Lens Dry Eye Questionnaire (CLDEQ-8), first and mean NIKBUT (F/M-NIKBUT), fluoresc…
Implantation of a custom intraocular lens with a 30-diopter torus for the correction of high astigmatism after penetrating keratoplasty.
2003
Abstract We present a 62-year-old woman who had implantation of an intraocular lens (IOL) with a torus of 30.0 diopters (D) in an eye after penetrating keratoplasty. The patient presented with cataract and a best corrected visual acuity of 20/400. Penetrating keratoplasty was performed in 1975 because of decompensated keratoconus. With a clear but inferiorly decentered corneal graft, visual acuity was limited because of keratoplasty-related high corneal astigmatism of 22.5@156 that could not be successfully treated with spectacles or contact lenses. A custom toric IOL with –30.0 D of cylindrical power was implanted in the capsular bag via a sclerocorneal tunnel incision. Additionally, a sph…
Optical quality of intraocular lenses after several years in the human eye
2013
The optical quality of explanted intraocular lenses (IOLs) was analysed to verify if their quality is maintained after having been in the human eye for several years. Twenty-five explanted IOLs were studied, 10 because of intraocular luxation and 15 from corneal donors. The dioptric power and modulation transfer function (MTF) were determined to discover the image quality of the IOLs. The spectral transmission was also established to ascertain whether the filter against ultraviolet (UV) radiation was still effective. The results show that the MTF of implanted IOLs is maintained and therefore so is the image quality they provide. Only decay in the MTF of some of the explanted IOLs was observ…
Dynamic in vitro dehydration patterns of unworn and worn silicone hydrogel contact lenses.
2008
Purpose: To evaluate the effect of wear on dynamic in vitro dehydration of silicone hydrogel (Si-Hi) contact lens (CL) using a previously described gravimetric procedure. Methods: Five different silicone hydrogel (Si-Hi) contact lenses (CL) were evaluated after being worn by patients under daily wear conditions for 15 days to 1 month. Lenses were conditioned and disinfected with a multipurpose solution after each day of wear. Lenses were left to dehydrate in an analytical balance under controlled conditions of temperature and relative humidity and the results compared with data from new lens samples of the same power and material. Several quantitative parameters were obtained and compared b…
Optical analysis to predict outcomes after implantation of a double intraocular lens magnification device.
2007
Purpose To analyze the effect of different optical parameters of the eye on the outcomes of implantation of a double intraocular lens (IOL) magnification device in patients with low vision. Setting Fundacion Oftalmologica del Mediterraneo, Valencia, Spain. Methods The eye's refraction and magnification before and after surgery were evaluated using a theoretical eye model based on paraxial optics approximation. Four parameters on which refraction and magnification are dependent were evaluated: anterior chamber depth (ACD), axial length (AL), mean keratometry (Km), and the distance between the 2 implanted IOLs. The 4 variables were analyzed separately in the first stage. Next, different combi…