Search results for " Lens"
showing 10 items of 510 documents
Chromatic-achromatic perimetry in four clinic cases: Glaucoma and diabetes
2015
Color perimetry has interesting clinical application for the diagnosis and detection of certain eye conditions, due to the variations that certain diseases can cause in chromatic thresholds, both in the red-green (RG) and the blue-yellow (BY) pathways.[1,2,3,4] The separate study of the visual function of both the chromatic and achromatic mechanisms could be more efficient in detecting sensitivity variations, and such variations would not be obscured by the intrusion of other mechanisms. Currently, the supply of conventional perimeters that are capable of performing a chromatic perimetry test is very limited and with reduced options regarding the possibility of choosing the physical charact…
Effect of sport-tinted contact lenses for contrast enhancement on retinal straylight measurements
2008
PURPOSE: To investigate the effect of two tinted contact lenses (CL) designed for outdoor sports activity on the psychometric determination of retinal straylight using the compensation comparison method. METHODS: Thirteen emmetropic subjects were randomly fitted with two different tinted Nike Maxsight (Bausch & Lomb, Rochester, NY, USA) CL in one eye, while the contralateral eye was fitted with a clear lens made of the same material (Optima 38, Bausch & Lomb). Three valid straylight measurements were taken on each eye before and a few minutes after lens insertion, when lens stabilization had occurred. RESULTS: The subjects' mean straylight values were 0.90 +/- 0.09 at baseline and 0.95 +/- …
In vitro power profiles of daily disposable contact lenses
2012
Abstract Purpose To evaluate and compare the distribution of refractive power within the optic zone of different soft contact lenses and to investigate the effect of lens decentration on the power profiles. Methods The Nimo TR1504 instrument was used to measure the optical power across different aperture diameters (from 1.5 mm to 5.5 mm in steps of 0.5 mm) of four daily disposable contact lenses: DAILIES TOTAL1, Proclear 1-Day, SofLens daily disposable and 1-DAY ACUVUE MOIST. Measurements were performed using a wet cell. Power data were evaluated when contact lenses were in its centered position and after inducing different amounts of lens decentration (from 0.2 mm to 1.0 mm in steps of 0.2…
True and Apparent Oxygen Permeabilities of Contact Lenses
1992
We studied the passage of oxygen through some commercially available contact lenses. Oxygen diffusion coefficients were determined by the time-lag method and a 201T Redher permeometer was used to measure the oxygen permeability and transmissibility by the polarographic method. The measurements were carried out at room temperature with 0.09% sodium chloride physiologic solution. The following types of lenses were tested: (1) 12 lenses of cellulose acetate butyrate (CAB) of a mean thickness of 0.194 mm (observed Dk approximately 6.3 barrers) (1 barrier is equivalent to 10(-11) cm3 of O2 (STP).cm2/cm3.s.mm Hg). (2) 13 lenses of a cross-linked polyhydroxyethyl methacrylate (2-HEMA), manufacture…
Biological oxygen apparent transmissibility of hydrogel contact lenses with and without organosilicon moieties.
2003
The instrument oxygen transmissibility (IOT) of organosilicon hydrogels, measured by electrochemical procedures, is 5-10 times larger than that of conventional hydrogels. A method is described that allows the estimation of the oxygen tension at the lens-cornea interface for closed- and open-eyelids situations by combining the IOT of the hydrogels and corneal parameters such as corneal thickness, corneal permeability and oxygen flux across the cornea. From these results the biological oxygen apparent transmissibility (BOAT) is obtained, an important parameter which an multiplication with the pressure of oxygen on the external part of the lens gives the oxygen flux onto the cornea. Contact le…
A swept-current magnetic lens plus Si(Li) electron spectrometer with simultaneous momentum and energy selection
1975
Abstract A combined swept-current magnetic lens plus Si(Li) electron spectrometer with simultaneous momentum and energy selection is presented. The spectrometer is intended for in-beam measurements of conversion electron lines up to several MeV in energy and for nanosecond lifetime determinations, as well as for off-beam studies of continuous beta-ray spectra and conversion lines from short-lived activities. The sweeping of the lens current is automatized and the energy selection, synchronously with the momentum, is performed using a simple digital window arrangement. The performance of the spectrometer is demonstrated in conversion electron and continuous spectrum measurements. Different v…
Three-Dimensional Printing of Nonlinear Optical Lenses.
2018
In the current paper, a series of nonlinear optical (NLO) active devices was prepared by utilizing stereolithographic three-dimensional printing technique. Microcrystalline NLO active component, urea, or potassium dihydrogen phosphate was dispersed in a simple photopolymerizable polyacrylate-based resin and used as the printing material to fabricate highly efficient transparent NLO lenses. The nonlinear activity of the printed lenses was confirmed by second-harmonic generation measurements using a femtosecond laser-pumped optical parametric amplifier operating at a wavelength of 1195 nm. The three-dimensional printing provides a simple method to utilize a range of NLO active compounds witho…
Double einzel lens extraction for the JYFL 14 GHz ECR ion source designed with IBSimu
2013
In order to improve the performance of the JYFL 14 GHz electron cyclotron resonance ion source (ECRIS) and initiate low energy beam transport (LEBT) upgrade at the University of Jyvaskyla, Department of Physics (JYFL) accelerator laboratory, a new ion beam extraction system has been designed and installed. The development of the new extraction was performed with the ion optical code IBSimu, making it the first ECRIS extraction designed with the code. The measured performance of the new extraction is in good agreement with the simulations. Compared to the old extraction the new system provides improved beam quality, i.e. lower transverse emittance values and improved structure of beam profil…
Optical power distribution of refractive and aspheric multifocal contact lenses: Effect of pupil size
2015
Abstract Purpose To evaluate the power profile within the optic zone of different designs of multifocal contact lenses (CLs) and to analyze how the effect of pupil size could impact on their optical performance. Methods The optical power distribution within the optic zones of multifocal CLs was measured by the Nimo TR1504 (LAMBDA-X, Belgium). The multifocal CLs under study were the Acuvue Bifocal, the Acuvue Oasys for Presbyopia, the PureVision Multifocal and the PureVision 2 for Presbyopia. Each design was considered in all their available addition powers. All lenses had a nominal power of −3.0D. At the same time, three lenses of each model were considered and five consecutive readings of …
Reliability of manual segmentation of cornea, contact lens and tear film using a high-resolution OCT
2015
In this study, we aimed to evaluate the intra/inter-session and intra/inter-observer variability of manual segmentation of thickness of the pre-lens tear film, contact lens (CL), post-lens tear film, epithelium, bowman’s layer, stroma and the whole cornea and CLs with a flat and a steep fit, using a commercial high-resolution spectral domain optical coherence tomographer (OCT). Two different observers obtained three repeated measures in two separate sessions. A high correlation was found between the values obtained by the two different observers, except for the thinner layers, epithelium, and Bowman’s layer. Inter-observer analysis showed a high consistency in the measurements obtained by b…