Navegando por Assunto "Toxoplasmose ocular"

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Acesso aberto (Open Access)
Avaliação da razão sinal ruído em eletrorretinografia multifocal: descrição do método e aplicação em toxoplasmose ocular
(Universidade Federal do Pará, 2009) CARVALHO, Aline Correa de; SOUZA, Givago da Silva; http://lattes.cnpq.br/5705421011644718; SILVEIRA, Luiz Carlos de Lima; http://lattes.cnpq.br/9383834641490219
The purpose of this work was to develop a quantitative analysis that allows, in healthful and patient with visual loss, to separate registers with signal correlated with the visual stimulation, of the registers that contain noise. System VERIS Science v6.0.5d was used to extract kernel first-class of the registers, and posterior exportation of the data for analysis in the MATLAB. In this environment of programming was carried the analysis of the main components (PCA), that is used to reduce the dimensionalidad of the data conserving its variation and minimizing the influence of the noise; the signal-to-noise analysis (SNR) of the multifocal responses (mfERG) using cumulative distribution SNR carried through in two intervals of time, one understanding only the signal and another one only the noise, for classification of the valid, diminished or absent responses. We have found that in a group healthy subjects, the noise and signal SNR cumulative distributions have not overlapped and occupy distinct ranges of SNR values in all subjects. By using a 1% criterion for false positives and false negatives, it was possible to define the borders of noise, low response, and signal SNR ranges. We have also applied this protocol to a three subject with visual loss due to ocular toxoplasmosis scares. In this case, there was a degree of overlapping between the noise and signal SNR distributions. It was still possible to separate the noise, low response, and signal SNR range by using the confidence limits for the distance between noise and signal boundaries obtained from the group of healthy subjects. The results of SNR evaluation were then used to display the mfERG waveforms in topographical plots that discriminate between reliable responses (signal), low responses, and no responses (noise). Using this approach, features of retinal topography, such as the optic nerve head, are more easily discriminate, whilst artifacts such as an erroneous central peak, are more easily rejected. The combinations of PCA to reconstruct mfERG waveforms with SNR evaluation are useful tools to analyze retinal topography both in healthy and impaired conditions.
Acesso aberto (Open Access)
Eletrorretinografia multifocal: desenvolvimento de método avaliativo e aplicação em pacientes com toxoplasmose ocular e investigação funcional da função retiniana em pacientes com malária, infectados pelo P. Vivax
(Universidade Federal do Pará, 2014-11-03) CARVALHO, Aline Correa de; SOUZA, Givago da Silva; http://lattes.cnpq.br/5705421011644718; SILVEIRA, Luiz Carlos de Lima; http://lattes.cnpq.br/9383834641490219
The current thesis was composed by two studies performed in parallel. The first purpose was the development of a reliable method to classify the electroretinographic responses and to validate this method in ocular toxoplasmosis. The second purpose was to investigate the effect of the acute use of chloroquine in the retina of vivax malaria patients, which received the standard treatment of the Ministry of Health of Brazil. The experimental tool of both studies was the multifocal electroretinogram (mfERG). In the first study the Veris system was used to test 10 healthy subjects to calculate a signal to noise ratio analysis in order to find the best values to separate normal responses from impaired retinal responses. The final results of this analysis were applied in three patients with visual loss due ocular toxoplasmosis. The results showed an optimal signal to noise ratio of 0.47 to separate waveforms with and without signal. The signal to noise ratio of 0.47, 0.44, 0.48, 0.57, 0.78, 1.21 were optimal to separate normal responses from progressively attenuated responses. The application of the signal to noise ratio analysis into ocular toxoplasmosis patients was able to map the retinal area with no activity evoked by the light. The second study was performed using mfERG to evaluate 48 vivax malaria patients which received chloroquine-based treatment. Their data were compared to 37 healthy subjects. The results showed that number of infections ranged between from 01 to 18 times. During the treatment, the mean dosage of intaken chloroquine was 5429 ± 782.3 mg. The cumulative dosage normalized to the body mass ranged from 14.58 to 545.45 mg/kg. No difference was observed in the mfERG amplitude and implicit time obtained from malaria patients and control group at any concentric rings of the visual field. There was no significant correlation between the retinal activity with the chloroquine cumulative dosage. It was concluded that the signal to noise analysis developed in this thesis can be used as a reliable method to study impaired retinal function, including the mapping of ocular toxoplasmosis consequences; and the acute use of chloroquine for malaria treatment caused no impairments to retinal activity recorded by mfERG.