0000000000616442
AUTHOR
Gatis Ikaunieks
showing 16 related works from this author
Visual Acuity in Myopes with Standard and Reversed Contrast Optotypes
2017
Abstract The aim of this study was to assess the visual acuity of myopes with standard and reversed contrast optotypes and to determine how the visual acuity of myopes is affected by optical defocus and the type of optical correction, either contact lenses or spectacles. Twenty-three myopic subjects (18 and 23 years old) with uncorrected vision had their visual acuity assessed with both standard and reversed contrast optotypes. The study also included 10 myopes with contact lens as well as habitual spectacle correction. The visual acuity for myopes with uncorrected vision was better with reversed than standard contrast optotypes. Better reversed contrast than standard contrast visual acuity…
<title>Assessment of ocular stereovision prevalence and eye dominance stability</title>
2005
The paper reports on the development of the equipment for studies of the eye dominance and ocular stereoprevalence by using black-and-white and color stereostimuli. The stereostimuli are separated either by color-filter goggles or phase separating liquid-crystal-shutter goggles. The stability of the stereoprevalence is studied by artificial step-by-step deterioration of the retinal image quality, particularly in the dominant eye. The stimuli are blurred using spatial Gaussian filtering. The polymer-dispersed-liquid-crystal cell placed in front of the dominant eye induces a controllable light scattering. The stimuli-blurring and light-scattering methods exhibit different influence on the eye…
Scattering and Depolarization in a Polymer Dispersed Liquid Crystal Cell
2008
An imaging polarimeter in transmission has been used to explore the effects of scatter and depolarization induced by a polymer dispersed liquid crystal cell. The experiment was carried out for three visible wavelengths. Both a directional and a scattered component can be distinguished in the light transmitted by this material. Whereas the directional component increased with voltage, the scattered portion decreased. This was a common behaviour for all three wavelengths. The polarimetric analysis revealed that the degree of polarization was also affected by changes in the voltage applied to the cell. Depolarization effects in the scattered component were usually high and decreased with volta…
Light scattering in artificial fog and simulated with light scattering filter.
2009
Disability glare, affecting e.g. road safety at night, may result either from intraocular light scattering or from external conditions such as fog. Measurements were made of light scattering in fog and compared with intraocular straylight data for normal eyes and eyes with simulated cataract. All measurements were made with a direct compensation flicker method. To estimate light scattering levels in fog, straylight measurements were carried in a fog chamber for different densities of fog. Density was characterized by the meteorological term visibility V and ranged from 7 to 25. Test distance for measurements in the fog was constant at 5 m. Cataract eye conditions were simulated by placing a…
Passive and active light scattering obstacles
2005
Simulation of vision pathologies and adverse viewing conditions in laboratory conditions requires optical phantoms with different level of light scattering. Such obstacles are designed as passive or active elements applying several technologies. We used for studies two kinds of solid state smart materials with electrically controllable light scattering - electrooptic PLZT ceramics, polymer dispersed liquid crystals PDLC and obstacles with fixed light scattering - composite of polymer methylmethaacrilat PMM together with grinded glass microparticles. Report analyzes optical characteristics of such obstacles - attenuation, scattering, depolarization of different wavelength light at various sc…
Redze paaugstinātas gaismas izkliedes apstākļos
2010
Elektroniskā versija nesatur pielikumus
Ocular performance evaluation
2019
Real and virtual three-dimensional (3D) imaging has found useful applications across different areas of health sciences and with the current rapidly progressive development stage we can expect that the use of 3D imaging soon will be a part of a daily visual load for medical personnel. To better understand the possible impact of prolonged work with 3D content on eye accommodative response and pupil size we compared two 3D imaging techniques - volumetric display that is real voxel-based system and anaglyph technique that is virtual pixel-based system. We have investigated accommodative lag and pupil responses in 38 emmetropic young adult after prolonged visual task with volumetric 3D display …
Cilvēka fizioloģijas un uztveres aktuālie pētījumi 2019.gadā : rakstu krājums
2019
Izdevumā apkopoti LU FMOF Optometrijas un redzes zinātnes nodaļas, kā arī citu struktūrvienību aktuālie pētījumi par cilvēka fizioloģiju un uztveri. 2019. gads Optometrijas un redzes zinātnes nodaļā ir zīmīgs ar nodaļas ilggadējo profesoru jubilejām. Savu apaļo dzimšanas dienu jau ir nosvinējis LU emeritus profesors Ivars Lācis, kurš ir devis lielu ieguldījumu Latvijas Universitātes attīstībā, kā arī viens no Latvijas optometrijas stūrakmeņiem. Šajā izdevumā bez zinātniskiem rakstiem ir īss ieskats viņa biogrāfijā, kura tapusi sadarbībā ar Latvijas Universitātes bibliotēku.
Effect of Light Scattering Simulation in the Eye on Different Color Stimuli Perception
2008
One of the factors which influences visual functions is intraocular light scattering. To assess the effect of light scattering and stimulus color on visual functions, visual acuity and retinal straylight were measured with and without light scattering occluder. For visual acuity measurements black Landolt optotypes on red, green and blue background were used. Retinal straylight was measured with a direct compensation method using the same colors stimuli. For one subject straylight was measured with 5 different light scattering levels of eye occluder.
Color stimuli perception in presence of light scattering.
2006
Perception of different color contrast stimuli was studied in the presence of light scattering: in a fog chamber in Clermont-Ferrand and in laboratory conditions where light scattering of similar levels was obtained, using different light scattering eye occluders. Blue (shortest wavelength) light is scattered in fog to the greatest extent, causing deterioration of vision quality especially for the monochromatic blue stimuli. However, for the color stimuli presented on a white background, visual acuity in fog for blue Landolt-C optotypes was higher than for red and green optotypes on the white background. The luminance of color Landolt-C optotypes presented on a LCD screen was chosen corresp…
<title>Factors affecting intraocular light scattering from different color straylight sources</title>
2008
Important optical parameter of the eye is intraocular light scattering. Straylight can reduce visual acuity, contrast sensitivity. It is one of the main factors for glare, especially for drivers at night, when there is light source some distance away from the fixation point. There are many factors, which can affect amount of light scattering in the eye. To assess the effect of the color of the straylight source on retinal image quality at different light scattering levels, retinal straylight was measured with and without light scattering occluder. Red, green and blue colors were choosed for straylight source. Psychophysical and electrophysiological methods were used to evaluate light scatte…
Colour vision experimental studies in teaching of optometry
2005
Following aspects related to human colour vision are included in experimental lessons for optometry students of University of Latvia. Characteristics of coloured stimuli (emitting and reflective), determination their coordinates in different colour spaces. Objective characteristics of transmitting of colour stimuli through the optical system of eye together with various types of appliances (lenses, prisms, Fresnel prisms). Psychophysical determination of mono- and polychromatic stimuli perception taking into account physiology of eye, retinal colour photoreceptor topography and spectral sensitivity, spatial and temporal characteristics of retinal receptive fields. Ergonomics of visual perce…
Accommodative Amplitude in School-Age Children
2017
Abstract In children, intensive near-work affects the accommodation system of the eye. Younger children, due to anatomical parameters, read at smaller distance than older children and we can expect that the accommodation system of younger can be affected more than that of older children. We wanted to test this hypothesis. Some authors showed that the norms of amplitude of accommodation (AA) developed by Hofstetter (1950) not always could be applied for children. We also wanted to verify these results. A total of 106 (age 7-15) children participated in the study. Distance visual acuity was measured for all children and only data of children with good visual acuity 1.0 or more (dec. units) we…
<title>The perception of isoluminant coloured stimuli of amblyopic eye and defocused eye</title>
2008
In routine eye examination the visual acuity usually is determined using standard charts with black letters on a white background, however contrast and colour are important characteristics of visual perception. The purpose of research was to study the perception of isoluminant coloured stimuli in the cases of true and simulated amlyopia. We estimated difference in visual acuity with isoluminant coloured stimuli comparing to that for high contrast black-white stimuli for true amblyopia and simulated amblyopia. Tests were generated on computer screen. Visual acuity was detected using different charts in two ways: standard achromatic stimuli (black symbols on a white background) and isoluminan…
Redzes asums miopiem ar standarta un apgriezta kontrasta optotipiem
2013
Darba mērķis bija novērtēt, kādi faktori var palielināt atšķirību starp standarta un apgriezta kontrasta redzes asuma vērtībām. Metode. Redzes asums ar abu polaritāšu stimuliem tika noteikts 20 nekoriģētiem jauniem miopiem un 10 miopiem ar ikdienā lietoto briļļu vai kontaktlēcu korekciju. 16 emetropi pētījumā piedalījās kā kontrolgrupa. Rezultāti. Emetropiem ar abu kontrastu stimuliem redzes asums bija vienāds. Koriģētiem miopiem redzes asums bija labāks ar apgriezta nekā standarta kontrasta stimuliem. Ar abiem korekcijas veidiem atšķirība bija līdzīga (~0.04 logMAR vienības). Bez korekcijas starpība pieauga (~0.16 logMAR). Secinājumi. Miopija ir būtisks faktors, kura dēļ var palielināties …
Cilvēka fizioloģijas un uztveres aktuālie pētījumi 2020. gadā
2020
Šajā izdevumā apkopoti LU FMOF Optometrijas un redzes zinātnes nodaļas un tās sadarbības partneru aktuālie pētījumi par cilvēka fizioloģiju un uztveri. 2020. gadā. Pētījumi ir saistīti ar redzes zinātni un klīnisko optometriju. Daļa rakstu ir latviešu, daļa angļu valodā. // This collection of publications consists of research done in Department of Optometry and Vision Science, Faculty of Physics, Mathematics and Optometry, University of Latvia. Reasearch topics are related with vision science and clinical optometry. Some of the articles are in Latvian, some of them are in English.