Navegando por Assunto "Acuidade visual"

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Acesso aberto (Open Access)
Acuidade visual e matriz extracelular no córtex visual primário: alterações associadas à privação monocular precoce e ao enriquecimento ambiental
(Universidade Federal do Pará, 2012-11-08) SILVA, Nonata Lucia Trévia da; DINIZ, Cristovam Wanderley Picanço; http://lattes.cnpq.br/2014918752636286; DINIZ JUNIOR, José Antônio Picanço; http://lattes.cnpq.br/3850460442622655
The aim of the present study is to analyze the influence of enriched environment on the visual acuity and on the distribution of perineuronal nets (PNNs) in the primary visual cortex of albino mice that underwent monocular deprivation during the critical period of postnatal development. Mice at 10th postnatal day, were monocular deprived through right eye-lid sutured (M, n = 16) and the control group animals were not submitted to any cirurgical procedures (B, n = 16). After weaning, on postnatal day 21, animals were subdivided in: standard environment (AP) and enriched environment (AE), constituting the following groups: M.AP, M.AE, B.AP and B.AE. After 3 months, animals were submitted to grating visual acuity tests, perfused and coronal sections of their brains processed for Wisteria floribunda agglutinin to posterior stereological quantification through optical fractionator method. B.AP animals present visual acuity of 0.48 cycles/degree, while those raised in enriched environment (B.AE) present a better performance at visual test, reaching 0.996 cycles/degree. Animals with monocular deprivation had significantly lower visual acuity (M.AP 0.18 cycles/degree; M.AE 0.4 cycles/degree). Stereological quantifications revealed that enriched environment increases type 1 and the total number of perineuronal nets at supragranular and granular layers in both hemispheres of deprived animals (ANOVA, two-ways, p < 0.05) and this difference at granular layer is due to an increase of perineuronal nets mainly at the right hemisphere (ipsilateral to the monocular deprivation). At infragranular layer, M.AE animals presented an increase only at the number of type 1 PNNs in both hemispheres.
Acesso aberto (Open Access)
Comparative neurophysiology of spatial luminance contrast sensitivity
(2011-06) SOUZA, Givago da Silva; GOMES, Bruno Duarte; SILVEIRA, Luiz Carlos de Lima
The luminance contrast sensitivity function has been investigated using behavioral and electrophysiological methods in many vertebrate species. Some features are conserved across species as a shape of the function, but other features, such as the contrast sensitivity peak value, spatial frequency contrast sensitivity peak, and visual acuity have changed. Here, we review contrast sensitivity across different classes of vertebrates, with an emphasis on the frequency contrast sensitivity peak and visual acuity. We also correlate the data obtained from the literature to test the power of the association between visual acuity and the spatial frequency of the contrast sensitivity function peak.
Acesso aberto (Open Access)
Enriched environment contributes to recovery of visual acuity and increases perineuronal nets in monocular-deprived animals
(2001-06) TRÉVIA, Nonata; ALMEIDA, Izabela Negrão Frota de; OLIVEIRA, Poliana Sampaio; WARWICK, Laura Vianna; MARQUES, Viviane; SANTOS, Denise Cristina dos; VIEGAS, Maria Luana Carvalho; DINIZ, Cristovam Wanderley Picanço; PAULO, Dario Carvalho
The aim of the present study was to analyze the influence of enriched environment on the distribution of perineuronal nets (PNNs) using a stereogically based unbiased protocol and visual acuity in adult Swiss albino mice that underwent monocular deprivation during the critical period of postnatal development. Eight female Swiss albino mice were monocular deprived were removed and cut at 70 µm thickness in a vibratome and processed for lectin histochemical staining with Wisteria floribunda agglutinin (WFA). Architectonic limits of area 17 were conspicuously defined by WFA histochemical staining, and the optical fractionator stereological method was applied to estimate the total number of PNNs in the supragranular, granular, and infragranular layers. All groups were compared using Student's t-test at a 95% confidence level. Comparative analysis of the average PNN estimations revealed that the EE group had higher PNNs in the supragranular layer (2726.33 ± 405.416, mean ± standard deviation) compared with the SE group (1543.535 ± 260.686; Student's t-test, p = .0495). No differences were found in the other layers. Visual acuity was significantly lower in the SE group (0.55 cycles/degree) than in the EE group (1.06 cycles/degree). Our results suggest that the integrity of the specialized extracellular matrix PNNs of the supragranular layer may be essential for normal visual acuity development.
Acesso aberto (Open Access)
Perda de sensibilidade ao contraste espacial de luminância em sujeitos com história clínica de hipovitaminose B1
(Universidade Federal do Pará, 2012) LOBATO, Jaisane Santos Melo; SOUZA, Givago da Silva; http://lattes.cnpq.br/5705421011644718
Vitamin B1 acts directly in the energetic metabolism and its deficiency causes several deficits to the nervous system, including those that occurs in vision that is an important and fundamental sense in the quality of life of the human beings. Studies have been shown that the contrast sensitivity estimative is a good biomarker for evaluation of the visual system and the own nervous system. The present study purposed to compare the contrast sensitivity of subjects with history of hypovitaminosis B1 with healthy subjects living in the cities of Imperatriz and João Lisboa in the Maranhão state from 2006 to 2009. This is a transversal, analytic, and case control study. It was investigated 18 patients with history of hypovitaminosis B1 (13 males, 5 females) with mean age 33.77 ± 9.33 years-old, whose had 35 eyes. The control group was composed by 40 subjects (80 eyes) from both sexes, and mean age 33.25 ± 9.3 years-old. Both groups had similar way of life. For psychophysical evaluation, it was used cathodic ray tubes, 21”, 6 x 5 degrees of visual angle. It was performed a nutritional evaluation of all investigated subjects, further visual acuity and contrast sensitivity evaluation. There were statistical differences between the contrast sensitivity of the control group and the group of the subjects with history of hypovitaminosis B1 at 4, 10, 15 e 20 cpd (two-way ANOVA, α = 0,05, Tukey post-hoc test). Most of the subjects with changes in healthy nutritional condition had changes in the visual evaluation. Clinical complains also had important relationship with visual losses.
Acesso aberto (Open Access)
Seletividade espacial de cor do potencial cortical provocado visual pseudoaleatório
(Universidade Federal do Pará, 2014-04-23) MARTINS, Isabelle Christine Vieira da Silva; SOUZA, Givago da Silva; http://lattes.cnpq.br/5705421011644718
Spatial selectivity to color stimulation has been investigated using invasive and non-invasive electrophysiological methods, and psychophysical methods. In non-invasive visual cortical electrophysiology, this issue was investigated using conventional methods of periodical stimulation; and averaging methods to extract responses. New methods of stimulation (pseudo-random presentation) and of signal extraction (cross-correlation) were developed and still lack their application to investigate the spatial selectivity of the cortical chromatic responses. The present study aimed to apply the new pseudo-random presentation electrophysiology method for study spatial selectivity of the color visual. Fourteen trichromats and 16 color-blind subjects were included in the sample. All the volunteers had normal or corrected visual acuity. They were evaluated by anomaloscopy HMC and Ishihara Plates test to be qualified the color vision in normal trichromacy or not. Sinusoidal gratings, 8º of visual angle, red-green contrast for 8 spatial frequencies among 0.2 a 10 cpd. The stimuli were temporally modulated by a binary m-sequence to simulate pattern reversal mode presentation. Veris system was used to extract the second order kernel, first and second slices (K2.1 e K2.2, respectively). After modeling of spatial frequencies response data with functions of difference of Gaussians, it was extracted the optimal spatial frequency and the bandwidth of spatial frequencies with amplitudes above of ¾ of the maximum amplitude of the spatial frequency-response function. Chromatic visual acuity also was estimated by the fit of a linear model to the amplitude data since from the optimal spatial frequency until the highest tested spatial frequency. In trichromats, the chromatic responses were found in the K2.1 and K2.2, whose showed different spatial selectivity. The negative components in the K2.1 and K2.2 showed band-pass tuning, and the positive component in the K2.1 showed low-pass tuning. The estimated chromatic visual acuity of the kernel components were comparable to those estimated by previous psychophysical studies. Different cellular components might contribute to the pseudo-random VECP generation. This new method is a potential candidate to an important tool for non-invasive evaluation of the human color vision.