Search results for "Contrast sensitivity"
showing 10 items of 115 documents
Optical and Visual Simulation of Standard and Modified Spherical Aberration Implantable Collamer Lens Post Myopic LASIK Surgery
2013
To evaluate the visual quality achieved in patients undergoing standard or modified implantable Collamer lens (ICL) to correct residual myopic error after laser-assisted in situ keratomileusis (LASIK) surgery.The adaptive optics visual simulator was used to simulate LASIK surgery of moderate and high myopia with a myopic regression corrected by a standard and modified ICL. Visual acuity (VA) and contrast sensitivity (CS) were measured in 14 subjects at 3- and 4.5-mm pupil. Point spread function and simulated retinal images were calculated.Comparing LASIK plus standard ICL and LASIK plus modified ICL simulations, for moderate myopia, VA improvement was less than 1 line in all VA contrasts an…
Effect of the color of the intraocular lens on optical and visual quality
2014
Purpose: To analyze the optical quality of intraocular lenses (IOL) with an orange (PC440Y) and a yellow (SN60AT) filter, and correlate these results with the visual quality of patients with these implants. Setting: Fisabio Oftalmología Médica, Valencia, Spain. Design: Randomized prospective study. Materials and Methods: The IOL optical quality was determined using the modulation transfer function (MTF) and the spectral transmission. The visual quality of 87 eyes with cataract (51 with orange filter and 36 with yellow filter) was determined by best corrected visual acuity (BCVA) and contrast sensitivity function (CSF) under photopic and mesopic conditions. To analyze the results, we use a S…
Presbiopijas korekcija ar multifokālajām intraokulārajām lēcām
2017
Bakalaura darbs ir uzrakstīts angļu valodā uz 47 lapaspusēm. Tas satur 3 zīmējumus, 20 tabulas, 39 literatūras avotus un pielikumu. Darba mērķis ir salīdzināt divu jaunu intraokulāro lēcu (difraktīvā trifokālā lēca un paplašināta fokusa dziļuma multifokālā lēca) efektivitāti presbiopija korekcijā pēc kataraktas operācijas. Pētījumi tika veikti 3 mēnešu periodā pēc kataraktas operācijas, kad tika novērtēta redzes kvalitāte, mērot redzes asumu un kontrasta redzi fotopiskos gaismas un mezopiskos krēslas apstākļos. Abi introokulāro lēcu veidi nodrošināja lielisku redzes asumu visos skata attālumos un pilnu neatkarību no brillēm. Taču kontrasta jūtība un redzes asums mezopiskos krēslas apstākļos…
Contrast sensitivity of the visual system in speckle imagery
1994
The contrast sensitivity function (CSF) of the whole visual system is determined with the use of coherent diffuse illumination. This function provides supplementary data about the effect of speckle on the ability of the visual system to perceive the spatial information contained in an image. The results show that speckle not only prevents perception of the finest details (highest frequencies) but also reduces the visibility of lower frequencies (especially where contrast is low). The difference between the CSF's determined with and without speckle is quantitatively very important. And the ratio between the two CSF's is a measure of the retinal ability to perceive contrast in the presence of…
Quality of vision with the Acri. Twin asymmetric diffractive bifocal intraocular lens system.
2007
To assess the quality of vision in patients who had implantation of asymmetric Acri. Twin bifocal diffractive intraocular lenses (IOLs) by evaluating distance and near visual acuities and photopic and mesopic contrast sensitivity under monocular and binocular conditions.Fernández-Vega Ophthalmological Institute, Oviedo, Spain.The study comprised 343 consecutive patients who had bilateral implantation of the Acri. Twin system: a distance-weighted 737D IOL and a near-weighted 733D IOL. Monocular and binocular best corrected distance visual acuities, best distance corrected near visual acuity, and distance contrast sensitivity under photopic (85 cd/m(2)) and mesopic (5 cd/m(2)) conditions were…
First-order visual interneurons distribute distinct contrast and luminance information across ON and OFF pathways to achieve stable behavior
2022
The accurate processing of contrast is the basis for all visually guided behaviors. Visual scenes with rapidly changing illumination challenge contrast computation because photoreceptor adaptation is not fast enough to compensate for such changes. Yet, human perception of contrast is stable even when the visual environment is quickly changing, suggesting rapid post receptor luminance gain control. Similarly, in the fruit fly Drosophila, such gain control leads to luminance invariant behavior for moving OFF stimuli. Here, we show that behavioral responses to moving ON stimuli also utilize a luminance gain, and that ON-motion guided behavior depends on inputs from three first-order interneuro…
Psychophysical and electrofunctional contrast sensitivity in cataractous patients treated with bendazac-lysine salt
1990
The clinical progression of the cataract may be influenced by drugs which reduce the denaturation of lens proteins. One of the most promising drugs is the bendazac-lysine salt. The drug was used in a double-blind study of a group of patients with initial cortical cataract in order to evaluate the changes in visual acuity and contrast sensitivity by means of a psychophysical and an electrophysiological method. After 6 months of treatment with bendazac the mean values of visual acuity showed a statistically significant increase in respect to baseline values, as well as an improvement of the threshold of contrast for most spatial frequencies. In the eyes treated with placebo there was no stati…
Images perceived after chromatic or achromatic contrast sensitivity losses.
2010
Purpose. We simulate how subjects with losses in chromatic and achromatic contrast sensitivity perceive colored images by using the spatiochromatic corresponding pair algorithm. Methods. This is a generalized version of the algorithm by Capilla et al. (J Opt Soc Am (A) 2004;21:176 –186) for simulating color perception of color deviant subjects, which incorporates a simple spatial vision model, consisting of a linear filtering stage, with a band-pass achromatic filter and two low-pass chromatic ones, for the red-green and blue-yellow mechanisms. These filters, except for the global scaling, are the subject’s contrast sensitivity functions measured along the cardinal directions of the color s…
Human contrast sensitivity in coherent Maxwellian view: effect of coherent noise and comparison with speckle.
1997
Lasers have been used in vision for measuring the neural contrast sensitivity function (CSF) by forming interference fringes on the retina. We distinguish among three kinds of illumination with lasers: incoherent (without noise), Maxwellian or coherent (with coherent noise), and diffuse coherent (with speckle). The three have different characteristics and different CSF's. A coherent imaging system is designed to measure the CSF with fully coherent illumination. This is the CSF of the whole visual system, although it is measured with gratings imaged on the retina. It therefore differs from the neural CSF's measured by other authors with partially coherent illumination. However, the neural CS…
Visual function after implantation of a diffractive aspheric trifocal intraocular lens
2016
Purpose To evaluate distance, intermediate, and near vision after bilateral implantation of a diffractive aspheric trifocal intraocular lens (IOL). Methods This study enrolled 204 eyes of 102 patients who had bilateral implantation of the AT LISA tri 839MP IOL. Monocular and binocular uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) (4 meters), monocular and binocular uncorrected near visual acuity (UNVA) and distance-corrected near visual acuity (DCNVA) (30, 40 centimeters), binocular uncorrected intermediate visual acuity (UIVA) and distance-corrected intermediate visual acuity (DCIVA) (50, 60, 70 centimeters), the defocus curve, and binocular photopic…