No / Precortical vision is mediated by three opponent mechanisms that combine receptoral outputs to form a luminance channel (L + M) and two chromatic channels, red-green (L/M) and blue-yellow (S/L + M). Here we ask the extent to which these basic color opponent mechanisms interact in the phenomenon of crowding, where nearby targets interfere with the processing of a central test target. The task was to identify the orientation of a Gabor patch while an annular plaid surrounded the patch. The radius of the annulus was varied in order to produce different separations of the test and flanker. The chromatic content of the Gabor and the annulus could be varied independently along the (L + M), (L/M), and (S/L + M) cardinal axes. For all targets, when the target and flanker shared the same chromaticity, performance decreased with decreasing separation of the target and annulus, i.e., a typical crowding effect was seen. When the test and flanker isolated different chromatic mechanisms, very little crowding was observed, even at the minimum separation of test target and annulus. In addition to this, intermediate chromaticities were found to produce intermediate levels of crowding. Finally, crowding effects using "half-wave rectified" stimuli suggest a locus for crowding effects beyond the level of color opponent mechanisms.

Yes / Adults with amblyopia ('lazy eye'), long-standing strabismus (ocular misalignment) or both typically do not experience visual symptoms because the signal from weaker eye is given less weight than the signal from its fellow. Here we examine the contribution of the weaker eye of individuals with strabismus and amblyopia with both eyes open and with the deviating eye in its anomalous motor position. The task consisted of a blue-on-yellow detection task along a horizontal line across the central 50 degrees of the visual field. We compare the results obtained in ten individuals with strabismic amblyopia with ten visual normals. At each field location in each participant, we examined how the sensitivity exhibited under binocular conditions compared with sensitivity from four predictions, (i) a model of binocular summation, (ii) the average of the monocular sensitivities, (iii) dominant-eye sensitivity or (iv) non-dominant-eye sensitivity. The proportion of field locations for which the binocular summation model provided the best description of binocular sensitivity was similar in normals (50.6%) and amblyopes (48.2%). Average monocular sensitivity matched binocular sensitivity in 14.1% of amblyopes' field locations compared to 8.8% of normals'. Dominant-eye sensitivity explained sensitivity at 27.1% of field locations in amblyopes but 21.2% in normals. Non-dominant-eye sensitivity explained sensitivity at 10.6% of field locations in amblyopes but 19.4% in normals. Binocular summation provided the best description of the sensitivity profile in 6/10 amblyopes compared to 7/10 of normals. In three amblyopes, dominant-eye sensitivity most closely reflected binocular sensitivity (compared to two normals) and in the remaining amblyope, binocular sensitivity approximated to an average of the monocular sensitivities. Our results suggest a strong positive contribution in habitual viewing from the non-dominant eye in strabismic amblyopes. This is consistent with evidence from other sources that binocular mechanisms are frequently intact in strabismic and amblyopic individuals.

La courbe de sensibilité au contraste – la façon selon laquelle la sensibilité diffère selon les fréquences spatiale – a été mesurée pour la première fois en 1956 (Schade, 1956). Elle diffère d’individu en individu et, quoiqu’elle ait été observée pour la première fois il y a plus de 60 ans, certains facteurs ayant un impact sur ces différences individuelles sont mal compris. La figure de Campbell-Robson est une grille sinusoïdale dont la fréquence spatiale varie sur l’axe des x et le contraste varie sur l’axe des y, de sorte que l’observateur perçoit une courbe directement sur la figure. Si cette figure contenait de l’information sur la courbe de sensibilité au contraste d’un individu, elle aurait pu être utilisée pour développer une méthode rapide permettant de mesurer la courbe de sensibilité au contraste. Or, les résultats de l’article 1 montrent qu’il n’existe que peu d’information à propos de la courbe de sensibilité au contraste dans la figure de Campbell-Robson. La maturation de la sensibilité au contraste n’est pas bien comprise. Puisque les études antérieures ont utilisé, entre autres, des méthodes et des tâches différentes, les résultats rapportés par ces études sont contradictoires. Nous nous sommes penchés sur la question dans l’article 2 en utilisant une méthode objective pour mesurer la sensibilité au contraste pour une grande étendue de fréquences spatiales (0.5 à 30 cycles par degré) et une grande étendue d’âges (4 à 27 ans). Au lieu d’utiliser l’âge comme variable catégorielle en séparant les participants en groupes, nous avons utilisé une méthode de régression locale (LOESS) pour utiliser l’âge comme variable continue et ainsi obtenir plus de précision sur l’âge de maturation. Les résultats montrent que la sensibilité devient semblable à celle d’un adulte autour de 12 ans pour les fréquences spatiales basses et hautes, et autour de 17 ans pour les fréquences spatiales moyennes. Après l’âge, la culture dans laquelle une personne grandit est un autre facteur pouvant avoir un impact sur la sensibilité au contraste. Dans l’article 3, nous avons vérifié l’effet de la culture sur la courbe de sensibilité au contraste en la mesurant de deux manières différentes chez des participant.es chinois.es et canadien.nes. Les résultats montrent que la courbe de sensibilité au contraste ne semble pas être différente chez les deux cultures. Compte tenu de différences interculturelles dans les fixations oculaires sur les visages, nous avons vérifié s’il existe des différences dans les fréquences spatiales contenues dans la représentation interne des visages chez les deux cultures. Nos résultats montrent que les participant.es chinois.es utilisent de plus basses fréquences spatiales et les participant.es canadien.nes utilisent de plus hautes fréquences spatiales pour reconnaître les visages. En somme, les résultats présentés dans cette thèse permettent de mieux comprendre les différences individuelles dans la sensibilité au contraste. / The contrast sensitivity function – the curve defining the way in which sensitivity differs according to spatial frequencies – was first measured in 1956 (Schade, 1956). The contrast sensitivity function differs from person to person and, although it was observed over 60 years ago, some factors which have an impact on these individual differences are not well understood. The Campbell-Robson figure is a sinusoidal grating on which the spatial frequency varies on the x axis and contrast varies on the y axis, resulting in a perceived curve, between the grating and the perceived gray area of the grating, directly on the figure. If this figure contained information on the contrast sensitivity function, it would have been useful to develop a quick method to measure it. However, the results of article 1 show that there is little information on the contrast sensitivity function contained in the Campbell-Robson chart. The way in which contrast sensitivity matures is not well understood. Because anterior studies used, among other things, different methods and tasks, the results they report vary greatly and are often contradictory. We have studied the question in article 2, using an objective method to measure contrast sensitivity for a large array of spatial frequencies (0.5 to 30 cycles per degree) and a large span of ages (4 to 27 years). Instead of using age as a categorial variable by separating the participants in age bins, we used a local regression technique (LOESS) in order to use age as a continuous variable and obtain a more precise estimate of the maturation age of contrast sensitivity. Results show that sensitivity becomes similar to an adult’s around 12 years old for low and high spatial frequencies, and around 17 years old for mid-range spatial frequencies. Other than age, the culture in which a person grows up is another factor that could have an impact on contrast sensitivity. In article 3, we verified the effect of culture on the contrast sensitivity function by measuring it using two different methods in Chinese and Canadian participants. Results don’t show that the contrast sensitivity function differs between the two cultures. Because of intercultural differences in ocular fixations on faces, we further verified if there are differences in the spatial frequencies contained in the internal representations of faces in the two cultures. Our results show that Chinese participants use lower spatial frequencies and Canadian participants use higher spatial frequencies when identifying faces. In sum, the results presented in this thesis help better understand individual differences in contrast sensitivity.

Indiana University-Purdue University Indianapolis (IUPUI) / Alzheimer’s disease (AD) is the most common age-related neurodegenerative disease. Many researchers believe that an effective AD treatment will prevent the development of disease rather than treat the disease after a diagnosis. Therefore, the development of tools to detect AD-related pathology in early stages is an important goal. In this report, MRI-based markers of neurodegeneration are explored as biomarkers of AD. In the first chapter, the sensitivity of cross-sectional MRI biomarkers to neurodegenerative changes is evaluated in AD patients and in patients with a diagnosis of mild cognitive impairment (MCI), a prodromal stage of AD. The results in Chapter 1 suggest that cross-sectional MRI biomarkers effectively measure neurodegeneration in AD and MCI patients and are sensitive to atrophic changes in patients who convert from MCI to AD up to 1 year before clinical conversion. Chapter 2 investigates longitudinal MRI-based measures of neurodegeneration as biomarkers of AD. In Chapter 2a, measures of brain atrophy rate in a cohort of AD and MCI patients are evaluated; whereas in Chapter 2b, these measures are assessed in a pre-MCI stage, namely older adults with cognitive complaints (CC) but no significant deficits. The results from Chapter 2 suggest that dynamic MRI-based measures of neurodegeneration are sensitive biomarkers for measuring progressive atrophy associated with the development of AD. In the final chapter, a novel biomarker for AD, visual contrast sensitivity, was evaluated. The results demonstrated contrast sensitivity impairments in AD and MCI patients, as well as slightly in CC participants. Impaired contrast sensitivity was also shown to be significantly associated with known markers of AD, including cognitive impairments and temporal lobe atrophy on MRI-based measures. The results of Chapter 3 support contrast sensitivity as a potential novel biomarker for AD and suggest that future studies are warranted. Overall, the results of this report support MRI-based measures of neurodegeneration as effective biomarkers for AD, even in early clinical and preclinical disease stages. Future therapeutic trials may consider utilizing these measures to evaluate potential treatment efficacy and mechanism of action, as well as for sample enrichment with patients most likely to rapidly progress towards AD.

This research is about evaluating vision in the periphery. Peripheral vision is of fundamental importance in the performance of our everyday activities. The aim of this thesis is to develop methods suitable for the evaluation of peripheral vision and to assess how different visual functions vary across the visual field. The results have application both within the field of visual rehabilitation of people with central visual field loss (CFL)and as well as in myopia research. All methods for assessing peripheral vision were implemented with adaptive psychophysical algorithms based on Bayesian statistics. A routine for time-efficient evaluation of peripheral contrast sensitivity was implemented and verified for measurements out to 30° in the visual field. Peripheral vision was evaluated for different properties of the stimuli: sharpness, motion, orientation, and extent. Optical quality was controlled using adaptive optics and/or corrective spectacles specially adapted for the peripheral viewing angle. We found that many peripheral visual functions improved with optical correction, especially in people with CFL. We also found improvements in peripheral contrast sensitivity for low spatial frequencies when stimuli drifted at 5 to 10 Hz; this applies both for people with normal vision and those with CFL. In the periphery, it is easier to see lines that are oriented parallel with respect to the visual field meridian. We have shown that this directional bias is present for both resolution and detection tasks in the periphery, even when the asymmetric optical errors are minimized. For accurate evaluation of peripheral vision, we therefore recommend using gratings that are oriented oblique to the visual  field meridian. The directional bias may have implications in how peripheral image quality affects myopia progression. Another proof that peripheral vision can influence central visual function is the fact that, when the stimulus extent was increased beyond the fovea, the blur in the stimulus was less noticeable. / Denna forskning handlar om att utvärdera synen i periferin. Vår perifera syn är ovärderlig i det dagliga livet. Målsättningen med denna avhandling är dels att utveckla metoder speciellt lämpade för perifer synutvärdering och dels att mäta hur olika synfunktioner varierar över synfältet. Resultaten har tillämpning både inom synrehabilitering för personer med centraltsynfältsbortfall och inom närsynthetsforskning. Adaptiv psykofysisk metodologi baserad på Bayesiansk statistik användes vid all utvärdering av det perifera seendet. Vi implementerade en rutin för tidseffektiv mätning av perifer kontrastkänslighet och verifierade den ut till 30° i synfältet. Den perifera synen utvärderades för olika egenskaper hos objektet: skärpa, rörelse, riktning och utbredning. Skärpan kontrollerades med hjälp av adaptiv optik och/eller glasögonkorrektion speciellt anpassad för den perifera synvinkeln. Vi fann att många periferasynfunktioner förbättras av optisk korrektion, särskilt för personer med centralt synfältsbortfall. Vi hittade även förbättringar i periferkontrastkänslighet för låga ortsfrekvenser när objektet modulerades med hastigheter mellan 5 och 10 Hz, vilket gäller både normalseende och personer med centralt synfältsbortfall. I periferin är det lättare att se linjer som är orienterade parallellt med synfältsmeridianen. Vi har visat att denna riktningsbias gäller både för upplösning och detektion i periferin, även när de asymmetriska optiska felen minimeras. För bästa mätnoggrannhet rekommenderar vi därför att använda randmönster som ligger snett relativt synfältsmeridianen. Denna riktningsbias skulle även kunna påverka hur den perifera bildkvalitén inverkar på utvecklingen av närsynthet. Ytterligare ett bevis för att perifer syn kan påverka den centrala synfunktionen är att, när objektets utbredning ökades, uppfattade personen det som mindre suddigt. / <p>QC 20160826</p>

O presente estudo investigou a função visual de pacientes com diabetes tipo 1 atletas e sedentários através de testes psicofísicos e eletrofisiológicos computadorizados de última geração. O objetivo foi investigar possíveis efeitos do exercício físico nas funções visuais. Materiais e Métodos: 33 pacientes com diabetes tipo 1, divididos em dois grupos experimentais: diabético atleta (n = 15; idade = 33,33 ± 6,78; tempo de doença =16,19 ± 6,63) e diabéticos sedentário (n = 18 idade = 28,94 ± 6,04; tempo de doença = 15,92 ± 8,46) e 40 sujeitos controles: controle atleta (n = 20; idade = 32,0 ± 5,61) e controle sedentário ( n = 20; idade = 27,05 5,60 ) foram submetidos a exames de: visão de cores e sensibilidade ao contraste Cambridge Colour Test - CCT; eletroretinograma por padrão reverso PERG e análises laboratoriais para quantificar óxido nítrico e endotelina por quimioluminescência e ELISA. As comparações entre os grupos foram feitas através de teste não paramétrico (Teste Kruskal-Wallis). Resultados: O grupo Diabético apresentou perdas significativas na amplitude do PERG, na discriminação de cores no eixo protan, área da elipse e nas frequências espaciais avaliadas da função da sensibilidade ao contraste, além de disfunção dos fatores endoteliais comparado ao grupo Controle. O grupo diabético atleta apresentou concentração maior de óxido nítrico comparado ao grupo Diabético sedentário. Não foram encontradas correlações entre os fatores endoteliais e as funções visuais. Conclusão: foram encontradas perdas funcionais na avaliação psicofísica e eletrofisiológica de pacientes com diabetes tipo 1. Os achados deste estudo confirmam a hipótese de que as perdas visuais sejam de origem neural pós - receptoral. Aumento na concentração de óxido nítrico encontrado em pacientes diabéticos atletas, confirmam os achados da literatura de que o exercício físico é capaz de aumentar a biodisponibilidade deste fator endotelial. Entretanto esse aumento de biodisponibilidade não se refletiu em recuperação das perdas nas funções visuais, uma vez que não houve correlação entre as alterações dos fatores endoteliais e os resultados da avaliação visual. A conclusão, em resumo, é de que o exercício físico não promoveu proteção dos danos visuais verificados em pacientes diabéticos / The study compared visual functions of sedentary and athlete patients with type 1 diabetes, and respective controls, using computerized psychophysical and electrophysiological tests. Materials and Methods: 33 Patients with type 1 diabetes, divided into two experimental groups: athlete diabetics (n = 15; age = 33.33 ± 6.78; rate of disease = 16.19 ± 6.63) and sedentary diabetics ( n = 18 age = 28.94 ± 6.04; rate of disease = 15.92 ± 8.46) and 40 control subjects: athlete control (n = 20; age = 32.0 ± 5.61) and sedentary control (n = 20; age = 27.05 5.60) were subjected to tests of: color vision and contrast sensitivity - Cambridge Colour Test - CCT; pattern electroretinogram (PERG) and laboratorial analysis of nitric oxide and endothelin using chemiluminescence and ELISA. The comparisons between groups were made through the nonparametric (Kruskal-Wallis test). Results: compared the control group, the diabetic group showed significant losses (1) in color discrimination in the protan axis and in ellipse area (2) in several spatial frequencies of the luminance spatial contrast sensitivity function; (3) a reduction in PERG amplitude and (4) dysfunction of endothelial factors. The athlete diabetic group showed increased concentration of nitric oxide compared to the sedentary diabetic group. No correlations were found between the endothelial factors and visual functions. Conclusion: losses in psychophysical and electrophysiological functions were found in patients with type 1 diabetes. The findings support the hypothesis that visual losses are due to the post-receptoral pathways. Increased nitric oxide concentration found in athlete diabetic patients, confirm the findings of the literature that physical exercise can increase the bioavailability this endothelial factor. However this increase in bioavailability was not reflected in the recovery of losses in visual functions, since there was no correlation between changes in endothelial factors and results of visual assessment. In conclusion, the exercise did not promote protection against visual losses due to diabetes

Objetivos: Avaliar a integridade das vias magnocelular (M) e parvocelular (P) atraves da percepcao de contraste e avaliar a sensibilidade no campo visual e respostas no ERG multifocal, em pacientes com esclerose multipla. Métodos e Resultados: Foram avaliados 29 pacientes (20F; 9M; idade media = 35,76 }10,91 anos) com diagnostico de esclerose multipla (15 com historico de neurite optica). Todos os pacientes apresentavam acuidade visual entre 0 e 0,1 logMAR. A percepcao de contraste foi avaliada atraves da funcao de sensibilidade ao contraste (programa PSYCHO; Cambridge Research System), com os limiares medidos em 0.2, 0.5, 1.0, 1.9, 5.3, 9.7 e 19.4 ciclos por grau; e do teste do Pedestal (Pokorny & Smith, 1997). O campo visual foi medido com o Campimetro Automatico de Humphrey, algoritmo SITA, estrategia central 24-2. O ERGmf foi registrado, utilizando o sistema VERIS, com 103 hexagonos. A analise foi baseada nos valores de amplitude e latencia de N1 e P1 das respostas de seis regioes predeterminadas de acordo com o mapa sugerido por Garway-Heath et al (2000), para os kernels de primeira e segunda ordem. Os pacientes foram divididos em 2 grupos: NO (antecedente de neurite optica) e SNO (sem antecedente de neurite optica). Resultados: O grupo NO nao diferiu do grupo SNO em nenhum dos testes, exceto nas medidas de amplitude do kernel de segunda ordem no ERGmf (Tukey HSD Test, PostHoc). Todos os pacientes mostraram uma reducao na percepcao de contraste, quando comparados ao grupo controle. Os resultados diferiram significativamente do grupo controle em todas as frequencias espaciais avaliadas na funcao de sensibilidade ao contraste (p < 0.001; ANOVA), e nos dois paradigmas avaliados pelo teste do Pedestal (p <0.05 ANOVA de medidas repetidas). As respostas do kernel de primeira ordem do ERGmf para ambos os grupos, quando comparados com o grupo controle, nao apresentaram diferenca estatistica significativa para as regioes analisadas (p > 0.05; ANOVA de medidas repetidas). As respostas de amplitude dos pacientes, para o kernel de segunda ordem apresentaram-se diferentes do grupo controle, com significancia estatistica para as areas 2, 3, 4, 5 e 6 (p < 0.05; ANOVA de medidas repetidas). Os resultados do campo visual mostraram reducao de sensibilidade nos pacientes em estudo, comparados ao grupo controle, com diferenca estatisticamente significante para todas as regioes (p <0.05; ANOVA de medidas repetidas). Conclusões: Aumento nos limiares de deteccao de contraste foram encontrados nos pacientes com esclerose multipla, em ambos os testes. O padrao de perda nas varias frequencias espaciais e em ambos os paradigmas analisados no teste do Pedestal, sugere um comprometimento nao seletivo das vias visuais, afetando tanto a via parvo como a magnocelular. As alteracoes nas respostas do ERG multifocal detectadas apenas no kernel de segunda ordem poderiam estar relacionadas a danos retrogrados a camada de fibras nervosas da retina causados pela desmielinizacao. Nao foram encontradas correlacoes com as perdas de sensibilidade no campo visual / Purpose: To assess the integrity of the magnocellular (M) and parvocellular (P) pathways by measuring contrast perception and to evaluate the visual field and multifocal ERG responses in patients with multiple sclerosis. Methods: 29 patients (20F, 9M, mean age = 35.76 } 10.91 years) diagnosed with multiple sclerosis were evaluated (15 with optic neuritis). All patients had visual acuity between 0 and 0.1 logMAR. The contrast perception was assessed by the measurement of contrast sensitivity function (program PSYCHO, Cambridge Research System) using spatial frequencies 0.2, 0.5, 1.0, 1.9, 5.3, 9.7 and 19.4 cycles per degree and the pedestal test (Pokorny & Smith, 1997). The visual field was measured using the central 24-2 SITA algorithm of the Humphrey Field Analyzer. The mfERG was recorded using the Veris system with 103 hexagons in which N1 and P1 amplitude and latency values of six predetermined areas according to the map suggested by Garway-Heath et al (2000) were used (first and second order kernels). Patients were divided into two groups: NO (with optic neuritis) and SNO (without optic neuritis). Results: The NO group did not differ from the SNO in any of the tests except for the second order kernel amplitudes in the mfERG (Tukey HSD posthoc test). All patients showed a reduction in contrast perception compared to the control group. The patients results were significantly different from the control groups at all spatial frequencies tested (p <0.001, ANOVA), and for the two paradigms of the pedestal test (p <0.05, ANOVA). The first order kernel responses in the mfERG showed no significant difference for both patient groups when compared with the control group (p> 0.05, ANOVA). The second order kernel amplitudes were different between patients and controls, with statistical significance for areas 2, 3, 4, 5 and 6 (p <0.05, ANOVA). The visual field results showed sensitivity reductions in the patients compared to controls, which was statistically significant for all regions (p <0.05, ANOVA). Conclusions: Increased thresholds for contrast detection were found in patients with multiple sclerosis in both tests. The pattern of loss in the various spatial frequencies and in both test paradigms of the Pedestal suggests a non-selective impairment of the visual pathways affecting both the parvo and magnocellular pathways. Changes in multifocal ERG responses found only in the second order kernel may be related to retrograde damage of the nerve fiber layer of the retina caused by demyelization. No significant correlation with the visual field losses was found

Objetivo: Avaliar repercussões da exposição ocupacional a uma mistura de solventes orgânicos sobre o desempenho visual de um grupo de frentistas. Método: Foram aplicados testes de ordenamento e discriminação de matizes, campo visual e sensibilidade ao contraste espacial de luminância em 25 frentistas (20 homens, M=36,4 anos, DP=8,9) e 25 controles sem histórico de exposição crônica a solventes (10 homens, M=33,8 anos, DP=8,8). As concentrações metabólitos urinários de tolueno (M=0,3 g/g de creatinina; DP=0,16) e xileno (M=0,1 g/g de creatinina; DP=0,02) e o tempo de trabalho (M=9,6 anos; DP=6,2) foram utilizados como indicativos da exposição dos frentistas. Os participantes foram submetidos a exame oftalmológico, e quando necessário, corrigir a acuidade visual para 20/20. Todas as medidas foram realizadas monocularmente com um olho escolhido ao acaso, com exceção do Potencial Visual Evocado Multifocal (PVEmf) e da campimetria. Para avaliar a visão de cores, utilizamos o Lanthony D15-d e Cambridge Colour Test 2.0. Na campimetria estática automatizada foi utilizado o protocolo branco-branco 24-2 do aparelho Humphrey Field Analyzer II-750i. A atividade elétrica visual cortical foi avaliada com o sistema de PVEmf Veris Science 5.2.4, utilizando um estímulo de 60 setores. A sensibilidade ao contraste espacial de luminância foi avaliada no teste Metropsis, para grades senoidais em 7 frequências espaciais de 0,2 a 20,0 cpg. Resultados: Os escores do grupo de frentistas e do grupo controle foram comparados pelo teste Mann-Whitney U. No teste de discriminação de cores (CCT), houve diferença estatística significativa entre controles e frentistas para a área total da elipse (p<0,01), elipticidade (p<0,05) e limiares nos eixos protan, deutan e tritan (p<0,05). No D15d houve diferença significativa entre os 8 dois grupos (p<0,01). Os dados da campimetria apresentaram diferenças significativas entre os dois grupos para as excentricidades de 90, 150 e 210, além dos valores de MD e PSD (p<0,05). Dos três frentistas avaliados com o PVEmf, todos apresentaram uma diminuição significativa (p<0,05) da amplitude do sinal (em relação a dados normativos) em um mínimo de 30 setores do campo visual, resultado que não foi observado no grupo controle. Nos testes de visão de cores, foi encontrada uma correlação (Spearman) positiva e significativa entre o tempo de trabalho e os índices do Lanthony D15d (p=0,52; p<0,05) e os limiares no eixo deutan (p=0,59; p<0,05). Na campimetria, houve correlações negativas significativas com o tempo de trabalho para a área da Fóvea (p=-051; p<0,05), e para os anéis de 30 (p=-0,46; p<0,05), 90 (p=-0,46; p<0,05) e 150 (p=-0,46; p<0,05). Não foi encontrada correlação significativa entre a sensibilidade ao contraste e o tempo de trabalho. Conclusões: Os resultados mostram alterações amplas e difusas no processamento visual em decorrência da exposição crônica a solventes orgânicos / Purpose: To evaluate the outcome of chronic occupational exposure to a mixture of solvents on the visual system of a group of gas station workers. Methods: 25 gas station workers (20 male; M=36,4 years old, SD=8,9) and 25 controls (10 male; M=33,8 years old, DP=8,8) with no history of chronic exposure to solvents were tested for hue discrimination and arrangement, spatial contrast sensitivity, visual field and multifocal VEPs. Urinary concentrations of toluene (M=0,3g/g of creatinine; Sd=0,16) and xylene metabolites (M=0,1 g/g creatinine; SD=0), along with the time of work (M=9,6 years; SD=6,2) were used as indicators of the exposure. The participants were submitted to an ophthalmologic examination and corrected the visual acuity to 20/20 whenever needed. All measurements were monocular (eye randomly chosen) and only one eye was tested, except for Multifocal Visual Evoked Potential (mfVEP) and the automated perimetry. Color was evaluated with the Lanthony D15d and Cambridge Colour Test 2.0. Automatic static perimetry used the white-on-white 24-2 protocol of the Humphrey Field Analyzer II-750i. Visual field was also evaluated with the mfVEP system Veris Science 5.2.4. Contrast sensitivity was measured with Metropsis software, using sine wave gratings of 0,2; 0,5; 1,0; 2,0; 5,0; 10,0 and 20,0 cpd. Results: The results for the two groups were compared using the Mann-Whitney U test. In the color discrimination test, the groups were significantly different for the thresholds in the three confusion axis tested (p<0,05), area of the ellipse (p<0,01) and ellipticity (p<0,05). In the color arrangement test, the two groups were significantly different (p<0,01). The automated perimetry results were also significantly different between groups for the 90, 150 e 210 eccentricity rings (p<0,05) and the MD and PSD values (p<0,05). Only three of the workers were tested with the mfVEP so far. All three had at least 30 sectors in the visual field 10 with significant loss of amplitude in the response (p<0,05, when compared to normative data). This result was not observed in the control group. The Spearman correlation coefficient was used to look for significant correlations between time of work and visual performance. For color vision, we found significant positive correlation between time of work and indexes of the Lanthony D15d (p=0,52; p<0,05) and deutan axis thresholds (p=0,59; p<0,05) for the CCT test. The analysis of sensitivity in eccentricity rings of perimetry data showed significant negative correlation with the time of work for the Fovea (p=-051; p<0,05) and rings of 30 (p=-0,46; p<0,05), 90 (p=-0,46; p<0,05) e 150 (p=-0,46; p<0,05). The contrast sensitivity data was not significantly correlated with time of work. Conclusions: The results presented here suggest that chronic occupational exposure to organic solvents leads to changes in the visual system function even when the exposure is within occupational safety limits. The results also suggest that the visual changes are extensive and diffuse

Objetivo: Avaliar repercussões da exposição ocupacional a uma mistura de solventes orgânicos sobre o desempenho visual de um grupo de frentistas. Método: Foram aplicados testes de ordenamento e discriminação de matizes, campo visual e sensibilidade ao contraste espacial de luminância em 25 frentistas (20 homens, M=36,4 anos, DP=8,9) e 25 controles sem histórico de exposição crônica a solventes (10 homens, M=33,8 anos, DP=8,8). As concentrações metabólitos urinários de tolueno (M=0,3 g/g de creatinina; DP=0,16) e xileno (M=0,1 g/g de creatinina; DP=0,02) e o tempo de trabalho (M=9,6 anos; DP=6,2) foram utilizados como indicativos da exposição dos frentistas. Os participantes foram submetidos a exame oftalmológico, e quando necessário, corrigir a acuidade visual para 20/20. Todas as medidas foram realizadas monocularmente com um olho escolhido ao acaso, com exceção do Potencial Visual Evocado Multifocal (PVEmf) e da campimetria. Para avaliar a visão de cores, utilizamos o Lanthony D15-d e Cambridge Colour Test 2.0. Na campimetria estática automatizada foi utilizado o protocolo branco-branco 24-2 do aparelho Humphrey Field Analyzer II-750i. A atividade elétrica visual cortical foi avaliada com o sistema de PVEmf Veris Science 5.2.4, utilizando um estímulo de 60 setores. A sensibilidade ao contraste espacial de luminância foi avaliada no teste Metropsis, para grades senoidais em 7 frequências espaciais de 0,2 a 20,0 cpg. Resultados: Os escores do grupo de frentistas e do grupo controle foram comparados pelo teste Mann-Whitney U. No teste de discriminação de cores (CCT), houve diferença estatística significativa entre controles e frentistas para a área total da elipse (p<0,01), elipticidade (p<0,05) e limiares nos eixos protan, deutan e tritan (p<0,05). No D15d houve diferença significativa entre os 8 dois grupos (p<0,01). Os dados da campimetria apresentaram diferenças significativas entre os dois grupos para as excentricidades de 90, 150 e 210, além dos valores de MD e PSD (p<0,05). Dos três frentistas avaliados com o PVEmf, todos apresentaram uma diminuição significativa (p<0,05) da amplitude do sinal (em relação a dados normativos) em um mínimo de 30 setores do campo visual, resultado que não foi observado no grupo controle. Nos testes de visão de cores, foi encontrada uma correlação (Spearman) positiva e significativa entre o tempo de trabalho e os índices do Lanthony D15d (p=0,52; p<0,05) e os limiares no eixo deutan (p=0,59; p<0,05). Na campimetria, houve correlações negativas significativas com o tempo de trabalho para a área da Fóvea (p=-051; p<0,05), e para os anéis de 30 (p=-0,46; p<0,05), 90 (p=-0,46; p<0,05) e 150 (p=-0,46; p<0,05). Não foi encontrada correlação significativa entre a sensibilidade ao contraste e o tempo de trabalho. Conclusões: Os resultados mostram alterações amplas e difusas no processamento visual em decorrência da exposição crônica a solventes orgânicos / Purpose: To evaluate the outcome of chronic occupational exposure to a mixture of solvents on the visual system of a group of gas station workers. Methods: 25 gas station workers (20 male; M=36,4 years old, SD=8,9) and 25 controls (10 male; M=33,8 years old, DP=8,8) with no history of chronic exposure to solvents were tested for hue discrimination and arrangement, spatial contrast sensitivity, visual field and multifocal VEPs. Urinary concentrations of toluene (M=0,3g/g of creatinine; Sd=0,16) and xylene metabolites (M=0,1 g/g creatinine; SD=0), along with the time of work (M=9,6 years; SD=6,2) were used as indicators of the exposure. The participants were submitted to an ophthalmologic examination and corrected the visual acuity to 20/20 whenever needed. All measurements were monocular (eye randomly chosen) and only one eye was tested, except for Multifocal Visual Evoked Potential (mfVEP) and the automated perimetry. Color was evaluated with the Lanthony D15d and Cambridge Colour Test 2.0. Automatic static perimetry used the white-on-white 24-2 protocol of the Humphrey Field Analyzer II-750i. Visual field was also evaluated with the mfVEP system Veris Science 5.2.4. Contrast sensitivity was measured with Metropsis software, using sine wave gratings of 0,2; 0,5; 1,0; 2,0; 5,0; 10,0 and 20,0 cpd. Results: The results for the two groups were compared using the Mann-Whitney U test. In the color discrimination test, the groups were significantly different for the thresholds in the three confusion axis tested (p<0,05), area of the ellipse (p<0,01) and ellipticity (p<0,05). In the color arrangement test, the two groups were significantly different (p<0,01). The automated perimetry results were also significantly different between groups for the 90, 150 e 210 eccentricity rings (p<0,05) and the MD and PSD values (p<0,05). Only three of the workers were tested with the mfVEP so far. All three had at least 30 sectors in the visual field 10 with significant loss of amplitude in the response (p<0,05, when compared to normative data). This result was not observed in the control group. The Spearman correlation coefficient was used to look for significant correlations between time of work and visual performance. For color vision, we found significant positive correlation between time of work and indexes of the Lanthony D15d (p=0,52; p<0,05) and deutan axis thresholds (p=0,59; p<0,05) for the CCT test. The analysis of sensitivity in eccentricity rings of perimetry data showed significant negative correlation with the time of work for the Fovea (p=-051; p<0,05) and rings of 30 (p=-0,46; p<0,05), 90 (p=-0,46; p<0,05) e 150 (p=-0,46; p<0,05). The contrast sensitivity data was not significantly correlated with time of work. Conclusions: The results presented here suggest that chronic occupational exposure to organic solvents leads to changes in the visual system function even when the exposure is within occupational safety limits. The results also suggest that the visual changes are extensive and diffuse

O presente estudo investigou a função visual de pacientes com diabetes tipo 1 atletas e sedentários através de testes psicofísicos e eletrofisiológicos computadorizados de última geração. O objetivo foi investigar possíveis efeitos do exercício físico nas funções visuais. Materiais e Métodos: 33 pacientes com diabetes tipo 1, divididos em dois grupos experimentais: diabético atleta (n = 15; idade = 33,33 ± 6,78; tempo de doença =16,19 ± 6,63) e diabéticos sedentário (n = 18 idade = 28,94 ± 6,04; tempo de doença = 15,92 ± 8,46) e 40 sujeitos controles: controle atleta (n = 20; idade = 32,0 ± 5,61) e controle sedentário ( n = 20; idade = 27,05 5,60 ) foram submetidos a exames de: visão de cores e sensibilidade ao contraste Cambridge Colour Test - CCT; eletroretinograma por padrão reverso PERG e análises laboratoriais para quantificar óxido nítrico e endotelina por quimioluminescência e ELISA. As comparações entre os grupos foram feitas através de teste não paramétrico (Teste Kruskal-Wallis). Resultados: O grupo Diabético apresentou perdas significativas na amplitude do PERG, na discriminação de cores no eixo protan, área da elipse e nas frequências espaciais avaliadas da função da sensibilidade ao contraste, além de disfunção dos fatores endoteliais comparado ao grupo Controle. O grupo diabético atleta apresentou concentração maior de óxido nítrico comparado ao grupo Diabético sedentário. Não foram encontradas correlações entre os fatores endoteliais e as funções visuais. Conclusão: foram encontradas perdas funcionais na avaliação psicofísica e eletrofisiológica de pacientes com diabetes tipo 1. Os achados deste estudo confirmam a hipótese de que as perdas visuais sejam de origem neural pós - receptoral. Aumento na concentração de óxido nítrico encontrado em pacientes diabéticos atletas, confirmam os achados da literatura de que o exercício físico é capaz de aumentar a biodisponibilidade deste fator endotelial. Entretanto esse aumento de biodisponibilidade não se refletiu em recuperação das perdas nas funções visuais, uma vez que não houve correlação entre as alterações dos fatores endoteliais e os resultados da avaliação visual. A conclusão, em resumo, é de que o exercício físico não promoveu proteção dos danos visuais verificados em pacientes diabéticos / The study compared visual functions of sedentary and athlete patients with type 1 diabetes, and respective controls, using computerized psychophysical and electrophysiological tests. Materials and Methods: 33 Patients with type 1 diabetes, divided into two experimental groups: athlete diabetics (n = 15; age = 33.33 ± 6.78; rate of disease = 16.19 ± 6.63) and sedentary diabetics ( n = 18 age = 28.94 ± 6.04; rate of disease = 15.92 ± 8.46) and 40 control subjects: athlete control (n = 20; age = 32.0 ± 5.61) and sedentary control (n = 20; age = 27.05 5.60) were subjected to tests of: color vision and contrast sensitivity - Cambridge Colour Test - CCT; pattern electroretinogram (PERG) and laboratorial analysis of nitric oxide and endothelin using chemiluminescence and ELISA. The comparisons between groups were made through the nonparametric (Kruskal-Wallis test). Results: compared the control group, the diabetic group showed significant losses (1) in color discrimination in the protan axis and in ellipse area (2) in several spatial frequencies of the luminance spatial contrast sensitivity function; (3) a reduction in PERG amplitude and (4) dysfunction of endothelial factors. The athlete diabetic group showed increased concentration of nitric oxide compared to the sedentary diabetic group. No correlations were found between the endothelial factors and visual functions. Conclusion: losses in psychophysical and electrophysiological functions were found in patients with type 1 diabetes. The findings support the hypothesis that visual losses are due to the post-receptoral pathways. Increased nitric oxide concentration found in athlete diabetic patients, confirm the findings of the literature that physical exercise can increase the bioavailability this endothelial factor. However this increase in bioavailability was not reflected in the recovery of losses in visual functions, since there was no correlation between changes in endothelial factors and results of visual assessment. In conclusion, the exercise did not promote protection against visual losses due to diabetes