Navegando por Autor "LACERDA, Eliza Maria da Costa Brito"

Agora exibindo 1 - 4 de 4

Acesso aberto (Open Access)
Avaliação visual de sujeitos expostos de forma ocupacional a solventes orgânicos através de métodos psicofísicos
(2011) LACERDA, Eliza Maria da Costa Brito; VENTURA, Dora Selma Fix; SILVEIRA, Luiz Carlos de Lima
Organic solvents are neurotoxic substances that can cause damaging effects in the visual system. Occupational exposure to these substances is common because they are used in a wide variety of activities. These effects can be quantified by specific psychophysical tests. The most commonly used tests for color vision assessment are arrangement tests, such as the Lanthony Panel D-15 desaturated test and the Farnsworth-Munsell 100-hue test, and for contrast sensitivity assessment, printed panel tests such as the MCT 8000 VISTECH, VCTS 6500VISTECH, and FACT 101 tests. Generally, these tests show color discrimination losses in the blue-yellow and red-green axis, and a decrease in contrast sensitivity, mainly at low spatial frequencies. There is a positive correlation between psychophysical results and biological environmental markers, but this correlation depends on the marker and on the kind of solvent to which the individuals are exposed. Factors such as alcohol and tobacco can interfere with the correlation of the results.
Acesso aberto (Open Access)
Contrast sensitivity of pattern transient VEP components: contribution from M and P pathways
(2013-12) SOUZA, Givago da Silva; GOMES, Bruno Duarte; LACERDA, Eliza Maria da Costa Brito; SAITO, Cézar Akiyoshi; SILVA FILHO, Manoel da; SILVEIRA, Luiz Carlos de Lima
The purpose of this study was to compare contrast sensitivity estimated from transient visual evoked potentials (VEPs) elicited by achromatic pattern-reversal and pattern-onset/offset modes. The stimuli were 2-cpd, achromatic horizontal gratings presented either as a 1 Hz pattern reversal or a 300 ms onset/700 ms offset stimulus. Contrast thresholds were estimated by linear regression to amplitudes of VEP components vs. the logarithm of the stimulus contrasts, and these regressions were extrapolated to the zero amplitude level. Contrast sensitivity was defined as the inverse of contrast threshold. For pattern reversal, the relation between the P100 amplitude and log of the stimulus contrast was best described by two separate linear regressions. For the N135 component, a single straight line was sufficient. In the case of pattern onset/offset for both the C1 and C2 components, single straight lines described their amplitude vs. log contrast relations in the medium-to-low contrast range. Some saturation was observed for C2 components. The contrast sensitivity estimated from the low-contrast limb of the P100, from the N135, and from the C2 were all similar but higher than those obtained from the high-contrast limb of the P100 and C1 data, which were also similar to each other. With 2 cpd stimuli, a mechanism possibly driven by the M pathway appeared to contribute to the P100 component at medium-to-low contrasts and to the N135 and C2 components at all contrast levels, whereas another mechanism, possibly driven by the P and M pathways, appeared to contribute to the P100 component at high contrast and C1 component at all contrast levels.
Acesso aberto (Open Access)
Investigação de danos visuais em pacientes diagnosticados com meningite criptocócica não associada à imunossupressão
(Universidade Federal do Pará, 2014-03-20) LACERDA, Eliza Maria da Costa Brito; SOUZA, Givago da Silva; http://lattes.cnpq.br/5705421011644718; SILVEIRA, Luiz Carlos de Lima; http://lattes.cnpq.br/9383834641490219
Cryptococcal meningitis is a severe infectious disease caused by Cryptococcus spp., which has high lethality and causes sensorial sequels. The most important sequels are visual impairments. The aim of this study was to describe the visual losses suffered by patients without immunosupression history, diagnosed with cryptococcal meningitis in order to indicate a possible mechanism and risk factors for the visual sequels. The work was composed by a case series study with cryptococcal meningitis without immunosupression history (n =7 patients, 14 = eyes) and an epidemiological study of all the cases of cryptococcal meningitis without immunosupression history notified during 14 years in the reference hospital of Para State (n = 113 cases). In the case series study, the visual functions of a sample of patients were studied by ophthalmological, psychophysical, and electrophysiological evaluation. The epidemiological study analyzed the medical records data focusing on visual impairment. It was observed that the studied patients in the case series study had visual acuity impairment. Even in patients without clinical complaints, color discrimination, luminance contrast sensitivity, and visual field were impaired. The results indicated central retina commitment as the principal responsible for a cascade of alterations that prevented the normal upstream image processing, at the visual cortex level. It is suggested that the observed visual dysfunction was due not only to optic nerve damage. The principal risk factors for the visual alterations observed in the epidemiological study were disease time before the beginning of the treatment and patient immunological response.
Acesso aberto (Open Access)
A visão através dos contrastes
(2013) SOUZA, Givago da Silva; LACERDA, Eliza Maria da Costa Brito; SILVEIRA, Vladímir de Aquino; ARAÚJO, Carolina dos Santos; SILVEIRA, Luiz Carlos de Lima
The first step in the information processing of visual stimuli corresponds to foton counting by photorreceptor cells. In the post-receptoral steps, information on the stimulus absolute intensity is converted in comparisons between information coming from adjacent retinal areas or successive moments. This metrics implemented by the visual system to quantify the stimulus is called contrast - spatial or simultaneous contrast and temporal or successive contrast. Contrast is essential to the generation of conscious visual perception in the domain of space and time and in three orthogonal color dimensions - black and white, blue and yellow, and green and red. A Bell-shaped curve delimits the thresholds of contrast detection as a function of spatial or temporal frequency. It is called contrast sensitivity function and is affected by several optical and neural factors. Different classes of neurons contribute to different regions of the contrast sensitivity function and their activities represent the work of visual processing pathways that begin in the retina and end in the visual cortex. Basic and clinical investigations have given support to the importance of the study of luminance (black and white) spatial contrast sensitivity as a tool to evaluate the visual function in normal and subjects affected by neuro-ophthalmologic dysfunctions.