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Filtros espectrais melhoram a eficiência da leitura e dos movimentos oculares: estudo longitudinal de 177 adultos

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A leitura é uma habilidade cognitiva complexa, fundamental para o sucesso acadêmico e profissional na vida adulta. As dificuldades de leitura podem envolver alterações no processamento subcortical da informação visual não responsivas às abordagens pedagógicas habituais voltadas para problemas cognitivos de decodificação grafema–fonema, lexicais ou de processamento fonológico. Neste contexto a intervenção terapêutica deve ser direcionada para a identificação do tipo e intensidade dos distúrbios visuais a serem corrigidos, o que permite uma conduta eficaz e personalizada diante das demandas laborais, acadêmicas e sociais de cada caso (Guimarães & Guimarães, 2013). Os exames oftalmológicos de rotina se restringem a quantificar a capacidade de visualizar estímulos estáticos de alto contraste (letra preta no fundo branco), patologias orgânicas do globo ocular, alterações binoculares e alinhamento entre os olhos. Problemas refracionais, como a miopia e o astigmatismo, degradam a acuidade visual e consequentemente a eficiência leitora, sendo as alterações ópticas habitualmente corrigidas por meio de óculos de grau. No entanto, a leitura requer a integração com outro centro de processamento visual, indo, portanto, além das habilidades relacionadas à alta resolução espacial aferidas pelo exame da acuidade visual e que são processadas pelo sistema parvocelular. Assim, a leitura proficiente depende não só do sistema parvocelular, mas também da integridade do sistema magnocelular, considerado o caminho visual dominante na leitura de textos por atuar na mediação da capacidade de identificar de forma rápida e sequencial as letras e ainda controlar a orientação visual da atenção, das fixações e da sincronia binocular (Greatrex & Drasdo, 1995, Chase, Ashourzadeh, Kelly, Monfette, & Kinsey, 2003; Stein, 2003, 2018). Exemplificando, para se ler um livro de 200 páginas, o sistema magnocelular deve controlar ambos os olhos para que façam centenas de milhares de movimentos sacádicos curtos da esquerda para a direita, com fixações estáveis (pausas entre as sacadas) de 200 a 400 milissegundos para a extração da informação visual e com poucos movimentos de correção da direta para a esquerda (Regressões). Em tarefas de leitura, os déficits magnocelulares levam a instabilidade no controle da coordenação dos olhos e dificuldade na correta fusão da imagem pelo cérebro, provocando distorções visuais das palavras e do texto mesmo na ausência de problemas refracionais (Allen, Dedi, Kumar, Patel, Aloo, & Wilkins, 2012, Monger, Wilkins, & Allen, 2015, Solan, Ficarra, Brannan, & Rucker, 1998, Stein, 2001). O clássico estudo de Livingstone, Rosen, Drislane, e Galaburda (1991) demonstrou anormalidades post-mortem nas camadas magnocelulares dos núcleos geniculados laterais de disléxicos, mas não nas camadas parvocelulares, quando comparados a um grupo controle de leitores típicos. Diferentes estudos corroboraram o achado de que disléxicos possuem menores respostas a estímulos rápidos e de baixo contraste (coerentes com déficits no sistema magnocelular), mantendo respostas normais a estímulos lentos ou de alto contraste (preservação do sistema parvocelular) (Gori, Seitz, Ronconi, Franceschini, & Facoetti, 2015, Pammer, & Wheatley, 2001). Leituras mais longas, excedendo a dez minutos, tendem a apresentar uma instabilidade progressiva na movimentação ocular, gerando uma dificuldade no processamento visual, com perda da qualidade e consequente estresse visual. Os principais sintomas do estresse visual são distorções visuoperceptuais, fotosensibilidade, irritabilidade e agitação sob luz fluorescente e ainda défice na percepção de profundidade (Guimarães, Vilhena, & Guimarães, 2017, Loew, & Watson, 2012, 2013). As distorções mais frequentemente reportadas são sombras e halos ao redor das palavras, espaçamentos irregulares em meio ao texto, e percepção de letras se movendo, vibrando ou se destacando do papel (Evans, Allen, & Wilkins, 2017, Stein, & Walsh, 1997). Os esforços para compensar essas dificuldades levam a queixas de cansaço visual progressivo, dor nos olhos, lacrimejamento, piscar excessivo, cefaleia ou enxaquecas (Kriss, & Evans, 2005, Scott et al., 2002). O estresse visual prejudica ainda a manutenção da atenção, a aprendizagem em sala de aula e inflige desgastes emocionais e ocupacionais, comprometendo o interesse e o apreço pela leitura. A intervenção terapêutica feita pela prescrição de lentes ópticas, com ou sem grau refracional, acrescidas de filtros para bloqueio específico e individual das faixas espectrais hipersensibilizantes regulariza a velocidade de transmissão do sistema magnocelular, reequilibrando a sua relação com o sistema parvocelular (Breitmeyer, & Williams, 1990, Croyle, 1998, Solan, Ficarra, Brannan, & Rucker, 1998, Ray, Fowler, & Stein, 2005, Guimarães, Vilhena, Pinheiro, & Guimarães, 2018). Estima-se que 13% das crianças no ensino fundamental apresentem melhoras significativas da taxa de leitura com o uso de lâminas espectrais (Garcia, Momensohn-Santos, & Vilhena, 2017). Os efeitos do tratamento com Filtros Espectrais nos casos de disfunções oculomotoras, fotofobia e cansaço visual em déficits de leitura podem ser analisados via rastreadores oculares (eye-trackers) (Vilhena, Freitas, Guimarães, & Pinheiro, 2018). Os movimentos oculares refletem os processos cognitivos relacionados à percepção visuoespacial, à análise semântica do texto e ao processamento de informações. Razuk, Perrin-Fievez, Gerard, Peyre, Barela, & Bucci (2018) verificaram que crianças disléxicas leram mais rápido e com menor duração da fixação ocular com o uso de um Filtro Espectral Verde. Os autores sugeriram que o filtro provavelmente facilitou a atividade cortical e diminuiu as distorções visuais. Estudos com tomografia e com ressonância magnética funcional corroboram esses achados, tendo observado uma redução da hiperexcitabilidade cortical com o uso da intervenção espectral (Chouinard, Zhou, Hrybouski, Kim, & Cummine, 2012, Denuelle, Boulloche, Payoux, Fabre, Trotter, & Géraud, 2011, Huang, Zong, Wilkins, Jenkins, Bozoki, & Cao, 2011, Katz, &Digre, 2016) e também a supressão dos sintomas clínicos em 90% dos pacientes portadores de enxaqueca induzida por estresse visual (Guimarães, 2010). A mensuração da leitura de adultos é um desafio psicométrico, uma vez que o efeito de teto em testes de leitura é presente inclusive na avaliação de crianças (Pinheiro, Vilhena, & Cunha, 2017). Rastreadores oculares são instrumentos valorizados nas Clínicas de Neurociências da Visão (Neurovisão) e nos consultórios neuropsicopedagógicos, pois fornecem parâmetros objetivos dos movimentos oculares envolvida na leitura de textos, que são primariamente subcorticais e involuntários. Este estudo, de delineamento longitudinal, investigou o efeito terapêutico de uma ampla gama de Filtros Espectrais, considerando os diferentes parâmetros envolvidos na movimentação ocular e habilidade de leitura. Métodos Participantes O Comitê de Ética em Pesquisa da Universidade Federal de Minas Gerais aprovou todos os procedimentos do estudo [Aprovação nº 49765115.0.0000.5149], o qual foi conduzido em total conformidade com o Código de Ética da World Medical Association (Declaração de Helsinki, 2008) para pesquisa envolvendo seres humanos. Foram selecionados retrospectivamente todos os 177 pacientes adultos atendidos entre 01/2013 a 02/2016, no Departamento de Neurovisão do Hospital de Olhos de Minas Gerais – Clínica Dr. Ricardo Guimarães. Os pacientes possuíam de 18 a 59 anos, com média de 30.6 anos (Desvio Padrão de 11.0), sendo 50% homens. Instrumentos Foi utilizado o Visagraph III Eye-Movement Recording System (Taylor Associates, New York) para a análise dos movimentos oculares durante a leitura de textos. Este rastreador ocular (eye-tracker) é composto por um par de óculos sem lentes, no qual está acoplado um sistema de captação por sensores infravermelhos, conectado a um software de análise de dados. Com exceção da variável Compreensão de Texto (habilidade de alta ordem), os parâmetros listados na Tabela 1 possuem controle primariamente subcortical e involuntário. Para eliminar a discrepância binocular, a média de ambos os olhos foi calculada para as variáveis Fixações, Regressões, Alcance Perceptual e Duração da Fixações, uma vez que as correlações bivariadas de Pearson foram acima de 0.97. Os Filtros Espectrais usados nos testes haviam sido prescritos para uso em tempo integral, incluindo em atividades que requeriam intensa atividade visual (por exemplo, leitura prolongada de textos). Cada participante havia sido submetido previamente a um protocolo detalhado envolvendo exames psicofísicos, clínicos e o diagnóstico específico do(s) tipo(s) de filtros(s) necessário(s) para o bloqueio completo das faixas de luz visível ou faixas espectrais hipersensibilizantes. A seleção dos filtros é feita por meio da exposição do paciente a estímulos estressores ao sistema visual, com subsequente análise do grau de alívio/supressão da maioria dos sintomas visuais objetivos e subjetivos, como por exemplo, o maior conforto obtido sob o uso do filtro ideal. Dado o número de filtros e combinações possíveis, há centenas de opções possibilitando alto grau de especificidade na seleção individual. Na amostra do presente estudo, foram selecionados de forma individual ou composta, 49 diferentes Filtros Espectrais. Procedimentos Todos os pacientes foram submetidos a um protocolo oftalmológico para adequada prescrição da correção refracional e, caso necessário, houve encaminhamento e tratamento visual prévio à seleção de Filtros Espectrais. O protocolo incluiu a análise da acuidade visual monocular e binocular para longe e para perto, pesquisa de aberrações de baixa e alta ordem, exame ortóptico, aferição da dominância ocular e estereopsia, e avaliação da visão de cores (Teste de Placas de Ishihara Pseudo-Isocromáticas 25 e Teste de Tonalidades D-15 Farnsworth-Munsell simples e desaturado), da sensibilidade ao contraste e do campo visual periférico dinâmico. Para a análise do padrão dos movimentos oculares, os sensores do rastreador ocular foram alinhados à borda externa da pupila de cada indivíduo. A primeira e as duas últimas linhas do texto foram desconsideradas automaticamente pelo software do Visagraph III™ com o objetivo de representar de maneira fidedigna o padrão oculomotor de leitura. O material de leitura consistia em um único parágrafo de texto em tinta preta, impresso em papel branco, em fonte Times New Roman, tamanho 18. Os textos foram lidos em voz alta, com uma distância de visualização de 40 a 45 cm, sob iluminação de escritório padrão (duas lâmpadas de teto fluorescentes branca fria, tubos de 60 cm de 20W, temperatura de cor correlacionada de 5.000K e ciclo de intermitência de 120 Hz). Após cada leitura, os participantes responderam dez questões fechadas sobre o conteúdo do texto recém lido. O padrão oculomotor de leitura (linha de base) foi analisado na primeira consulta, sendo considerado como condição pré-teste, sem o uso de filtros. A consulta de retorno foi considerada como pós-teste, condição onde o Filtro Espectral fora usado de forma continuada e em tempo integral. A média de tempo entre o pré-teste e o pós-teste foi de 18 meses. Análise estatística O IBM SPSS Statistics (versão 21.0, Chicago, Illinois, EUA) foi utilizado para todas as análises de dados. Para examinar os efeitos da intervenção com Filtros Espectrais nos movimentos oculares foi conduzida uma série de ANOVA oneway, com F ajustado de acordo com o método de Greenhouse-Geisser. Para estabelecer a significância clínica das diferenças, o d de Cohen foi calculado para determinar o tamanho do efeito e foi interpretado usando os critérios de Cohen (1988) de 0.2 para um efeito pequeno, 0.5 para um efeito médio e 0.8 para um efeito grande. O valor de p inferior a 0.05 foi considerado estatisticamente significativo. RESULTADOS Após o tratamento com o uso de Filtros Espectrais (média de 18 meses entre condições), os participantes apresentaram uma redução moderada (d = 0.57, 0.54 e 0.49) e significativa (p < 0.0001) de -33% no número de Fixações oculares, de -46% no número de Regressões e de -18% na dificuldade da Direção Correta Esquerda–Direita, quando comparados com a linha de base (ver Tabela 2 e Figura 1). Houve um aumento moderado (d = 0.50 a 0.68) e significativo (p < 0.001) de 43% no Alcance Perceptual, de 29% no número de palavras lidas por minuto e de 11% na Compreensão de Texto. A Eficiência Relativa da leitura apresentou um forte aumento de 79% após o tratamento (d = 1.09, p < 0.001). Houve uma melhora, com efeito pequeno (d = 0.30) e significativo (p = 0.0008), de 7% na Correlação Binocular. A Duração da Fixação não apresentou diferença significativa entre testagens (p = 0.48). Discussão O tratamento com Filtros Espectrais produziu um efeito moderado na melhora da atividade oculomotora na leitura de adultos. Após a intervenção (pós-teste) registrou-se um menor número de Fixações e de Regressões oculares em paralelo a uma maior correlação binocular, o que evidencia maior facilidade na focalização do mesmo número de palavras. O maior alcance perceptual proporciona uma melhor capacidade cognitiva para armazenar e manipular a informação, habilidade fundamental na decodificação automática das palavras. Essa capacidade permitiu um aumento de 29% na velocidade de leitura, com 58 palavras lidas a mais por minuto. Os resultados mostram que o bloqueio espectral seletivo pode aprimorar a extração da informação visual com o aumento da eficiência, fluência e compreensão leitora. Esses achados sugerem uma melhor redistribuição da ativação cortical, como encontrado em outros estudos (Chouinard, Zhou, Hrybouski, Kim, & Cummine, 2012, Denuelle, Boulloche, Payoux, Fabre, Trotter, & Géraud, 2011). Soares e Gontijo (2016) publicaram uma revisão da literatura, composta por 16 trabalhos, na qual foi evidenciado que há uma base bioquímica, genética e imunológica envolvida nos pacientes que apresentam estresse visual. Estudos assinalaram quem há uma diferença na proporção de lipídios no sangue (p < 0.05; d > 0.08; menor colesterol total e mais ácido heptadecanoicono plasma) e de aminoácidos e ácidos orgânicos na urina (p < 0.05; d > 0.05), sinalizando um metabolismo anormal associado a alterações de natureza sistêmica e imunológica. A revisão sistemática de Evans e Allen (2016) mostraram que a intervenção com Filtros Espectrais, além de ser segura e não invasiva, alivia os sintomas de astenopia e melhora o desempenho de leitura dos pacientes com estresse visual. Estes mesmos autores ressaltaram a importância do diagnóstico diferencial entre os casos de estresse visual com aqueles envolvendo erros refrativos, heteroforia descompensada e déficits na amplitude de acomodação, por serem também indutores de astenopia e/ou intensificadores dos sintomas de estresse visual. Em um artigo com quatro experimentos, Gori, Seitz, Ronconi, Franceschini, & Facoetti (2015) verificaram: 1) a presença de dificuldade na percepção de movimento em disléxicos quando comparados a dois grupos controles; 2) que a percepção de movimento visual de crianças na fase de pré-leitura prediz o desenvolvimento leitor; e que 3) os treinamentos no sistema magnocelular visual levam a uma melhor habilidade de leitura em crianças e adultos com dislexia do desenvolvimento. Gori, Seitz, Ronconi, Franceschini, & Facoetti concluíram que há de fato uma relação causal entre déficit no sistema magnocelular e a dislexia, fechando um debate de 30 anos. Flint e Pammer (2018) verificaram, em um estudo com dois experimentos, que adultos analfabetos obtiveram o mesmo desempenho do que os leitores normais e semianalfabetos em tarefas temporais e espaciais específicas do sistema magnocelular visual, tendo todos os três grupos um desempenho melhor do que o grupo de leitores disléxicos. O desempenho inferior dos disléxicos ocorreu tanto no experimento 1 com um teste de coerência do movimento (F(3, 79) = 104.9, p < 0.0001, d = 0.81), quanto no experimento 2 com o teste Frequency-doubling Illusion (F(3, 79) = 283.8, p< 0.005, d = 0.86). Os autores concluem que essa falha funcional da via visual dorsal na dislexia provavelmente não é consequência da falta de leitura, responsabilizando como causa o processamento magnocelular. Utilizando de analogia no título do artigo, Flint e Pammer consideram que o ovo veio primeiro que a galinha, assim, o déficit magnocelular veio primeiro que a dislexia. O presente estudo acompanhou 177 adultos que fizeram tratamento com uma ampla variedade de Filtros Espectrais, prescritos individualmente. Por meio de parâmetros objetivos de rastreamento ocular, foi demonstrado que houve uma melhora da eficiência dos movimentos oculares e da habilidade de leitura, com elevada significância estatística e moderado efeito clínico. A oculomotricidade está sob controle cortical e subcortical e responde a mecanismos de controle inibitórios que controlam o tempo de fixação, o alcance sacádico e a cognição e que afetam também a coordenação oculomotora binocular fina quando se percorre uma linha de texto. As lentes espectrais suprimiram ou reduziram as três principais queixas visuais dos pacientes: a sensibilidade à luz que limita a legibilidade, o conforto e a duração máxima da leitura, as disfunções oculomotoras que afetam a coordenação binocular fina quando se percorre uma linha de texto; e a disfunção acomodativa que altera a clareza textual. Houve, também, o reajuste da composição espectral e redução da luminância pela alteração do locus do feixe luminoso na retina e redução da intensidade da luz associada ao bloqueio seletivo dos comprimentos de onda hipersensibilizantes (Willeford, Fimreite, Ciuffreda, 2016). Conclusão Pacientes adultos, após o tratamento com Filtros Espectrais, apresentaram uma melhora significativa da habilidade de leitura e dos parâmetros oculomotores envolvidos no rastreamento visual do texto, quando comparados com a linha de base. Foi verificada uma forte melhora do parâmetro Eficiência Relativa da leitura. A redução no número de fixações oculares permite a estabilidade da imagem na região foveal. A redução no número de Regressões melhorou a fluência de leitura, o que reduz a dificuldade dos movimentos sacádicos na direção esquerda–direita. A melhora dos parâmetros oculomotores com o uso de Filtros Espectrais favoreceu a capacidade cognitiva e o armazenamento e manipulação da informação, culminando com a melhor compreensão do texto. Filtros Espectrais são uma intervenção oftalmológica não-invasiva e não-medicamentosa que melhoraram a eficiência de leitura em adultos com fotofobia, dificuldades de leitura, cansaço visual e sobrecarga sensorial podendo ser usados acrescidos a lentes ópticas com e sem correção refracional.

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Tradicionalmente oftalmologistas têm dedicado a maior parte de sua atenção ao estudo e correção dos erros refracionais, alterações da binocularidade e alinhamento entre os olhos e ao estudo de doenças oculares1. Embora saibamos que os olhos têm a mesma origem embriológica e representem uma exteriorização do cérebro, pouca atenção é dada a esta relação durante a formação do oftalmologista como especialistas bem como na assistência clínica2. Uma boa visão depende de dois pontos fundamentais. A primeira é a condição anatô­ mica, fisiológica e correlação óptica das estruturas dos nossos olhos, tais como a córnea e o cristalino, lentes que determinam o foco de luz exatamente sobre a retina ou da íris onde é feito o controle dinâmico da luminosidade. A segunda é a condição neurossensorial onde estímulos fotoquímicos são processados em sistemas integrados corticais produzindo habilidades que se desenvolvem progressivamente e com vigor especial nas diversas "janelas de oportunidade" onde o desenvolvimento de redes neuronais é mais favorecido3. Vários sinais e sintomas associados aos possíveis distúrbios neurovisuais ou processamento visual central ainda vêm sendo frequentemente ignorados pela classe oftalmoló­ gica que os considera como não pertencentes à sua esfera de atuação e que tende a referi-los a neurologistas, psiquiatras, psicólogos e psicopedagogos4. Na otorrinolaringologia, a avaliação do processamento auditivo central e sua utilidade diante de uma audiometria normal foi motivo de reserva e inúmeras contestações. A resistência na assimilação de novos conhecimentos produzidos pela neurociência não é exclusiva da classe oftalmológica. Nos Estados Unidos há um debate criado em grande parte a partir de um artigo escrito por Claude Lenfant e publicado no New England Journal of Medicine em 2003 questionando a não utiliza­ ção em clínica de uma enorme reserva de conhecimentos científicos produzidos pela ciência básica. O autor Lenfant questiona a atitude de resistência de "parte da medicina ortodoxa que mesmo diante de evidências científicas e resultados de estudos de alto custo financiados por verbas federais nos EUA vem restringindo o acesso dos pacientes a melhores opções de tratamento, recuperação e até de sobrevida e retardando a plena aceita­ ção de práticas referendadas pela comunidade científica"5.
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Spectral filters are used to treat light sensitivity in individuals with traumatic brain injury (TBI); however, the effect of these filters on normal visual function has not been elucidated. Thus, the current study aimed to determine the effect of spectral filters on objectively-measured visual-evoked potential (VEP) and alpha-wave responses in the visually-normal population. The full-field (15°H×17°V), pattern-reversal VEP (20' check size, mean luminance 52cd/m(2)) was administered to 20 visually-normal individuals. They were tested with four Intuitive-Colorimeter-derived, broad-band, spectral filters (i.e., gray/neutral density, blue, yellow, and red), which produced similar luminance values for the test stimulus. The VEP N75 and P100 latencies, and VEP amplitude, were recorded. Power spectrum analysis was used to derive the respective powers at each frequency, and peak frequency, for the selected 9-11Hz components of the alpha band. Both N75 and P100 latencies increased with the addition of each filter when compared to baseline. Additionally, each filter numerically reduced intra-session amplitude variability relative to baseline. There were no significant effects on either the mean VEP amplitude or alpha wave parameters. The Intuitive Colorimeter filters significantly increased both N75 and P100 latencies, an effect which is primarily attributable (∼75%) to luminance, and in some cases, specific spectral effects (e.g., blue and red). VEP amplitude and alpha power were not significantly affected. These findings provide an important reference to which either amplitude or power changes in light-sensitive, younger clinical groups can be compared. Copyright © 2015 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.
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To investigate whether the clinical tests used in routine eye examinations can identify adults whose reading rate increases with their preferred coloured overlay(s).Methods Routine optometric tests were used to measure 73 undergraduate students’ refractive error, visual acuity, stereo-acuity, amplitude of accommodation, near point of convergence, associated heterophoria at near, colour vision and ocular motility. Participants chose an overlay or combination of overlays with colour optimal for clarity, and completed the Wilkins Rate of Reading Test with and without an overlay(s) of this colour.ResultsOverall, there was a significant increase in reading speed with overlay (t(72) = −5.26, p < 0.0005). Twenty-six participants (36%) increased their reading rate by >5% with their chosen coloured overlay(s). Ten participants (14%) had a reading speed increase of >10%. The increase in reading speed was not significantly associated with any clinical finding.Conclusion Tests which are completed in routine eye examinations did not identify those participants who benefitted from coloured overlays in terms of reading speed.
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Previous investigations of the visual-perception disorder scotopic sensitivity syndrome (SSS), also known as Meares-Irlen syndrome, have identified several clinical features of symptom manifestation which are strikingly similar to those found in attention deficit/ hyperactivity disorder (ADHD). We surveyed the incidences of nine widely-recognised symptoms of SSS in individuals (n = 76), of whom one sub-group (n = 12) was comprised of subjects diagnosed with ADHD by qualified healthcare providers. The prevalence of each SSS symptom in the ADHD sub-group was compared to a second sub-group of diagnosed SSS individuals (n = 18), and also to a group of appropriately matched controls (n = 46). The data showed a remarkable lack of significant variations between the ADHD-diagnosed and SSS-diagnosed groups. In contrast, highly significant variations between the ADHD-diagnosed and control groups were clearly evident. The degree of symptom overlap between the ADHD and SSS disorders may be far stronger than previously reported and it is likely that many individuals with SSS may be misdiagnosed with ADHD.
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We manipulated the accommodative response using positive and negative lenses to study any association between symptoms of pattern glare and accommodation. Two groups of eighteen young adults were selected from seventy-eight on the basis (i) that their rate of reading increased by 5% or more with an overlay compared to their rate without it, and (ii) that they reported more than 2 symptoms of pattern glare (group 1) or had no such increment in reading speed and reported fewer than 3 symptoms (group 2). Under double-masked conditions participants observed at 0.4 m a pattern of stripes while measurements of accommodation were made using an open field autorefractor with and without positive and negative trial lenses (0.75 D), and with and without a coloured overlay. Pattern glare was also assessed with and without the trial lenses. Without lenses, the mean accommodative response in group 1 was 1.55 D, a lag of 0.95 D +/- 0.24 D relative to the demand. The lag decreased by 0.43 D (p < 0.0001) when the chosen overlay was used, an effect that was not shown in group 2 even when lag increased with negative trial lenses (p = 0.13). In both groups, pattern glare scores were reduced by the trial lenses, but were unaffected by the sign of the lenses. This suggests that symptoms of pattern glare are not strongly associated with accommodative response.
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Prior investigations of scotopic sensitivity or Meares-Irlen syndrome have identified several features also found in attention deficit/hyperactivity disorder, chronic fatigue syndrome, and a subtype of dyslexia in which visual recognition is the primary deficit. In particular, anomalies in lipid metabolism, including low essential fatty acid status and decreased serum cholesterol, have been identified in all three disorders. Genetic expression of the transporter molecule apolipoprotein B-100 (APOB) has been correlated with abnormal lipid metabolism, particularly in relation to levels of cholesterol. Cholesterol esters are important carriers of essential fatty acids entering the retina. The APOB gene coding for apolipoprotein B-100 is located on the short arm of Chromosome 2, and closely neighbours a gene (DYX3) known to confer susceptibility to dyslexia. The APOB locus is also recognised as being one of the most highly polymorphic regions of the human genome, and thus provides a promising tool for genetic researchers. In this pilot study, certain allelic variants of the APOB gene were more common in participants diagnosed with Meares–Irlen syndrome than in individuals without the condition. This study appears to be a first in which a condition known to cause reading difficulties has been associated with the APOB gene.
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The aim of this study is to evaluate the data from a participant in a reading study who had a diagnosis of Meares-Irlen syndrome/visual stress (MISViS). MISViS is characterised by visual distortions and somatic issues, which are remediated using coloured filters. The authors present a case study providing descriptive neurobiological comparisons of MISViS versus a control group. The study involved eleven English language speakers who participated in behavioural and neuroimaging versions of a language experiment with varied proportions of regular and exception words. Behavioural measures included accuracy and response times. Neuroimaging was conducted using a 1.5T Siemens Sonata MRI. The MISViS participant's data were removed from the overall experiment and analysed as a case study. Impulse response functions (IRFs) and percentage of active voxels were extracted from four regions of interest: BAs 17, 18, 19, and the postcentral gyrus (PG) and two control regions (BA6 and left BA45). The results indicated that significant differences existed between the control group and the MISViS participant for IRF intensity in two regions (BA6 and PG) and percentage of active voxels in four regions (BA17, BA19, PG, and BA6). No significant differences occurred in left BA45 for either variable of interest. No significant differences were found for behavioural measures. In conclusion, our findings offer one of the first neurobiological descriptions of differences in IRF intensity and percentage of active voxels in visual and somatosensory cortex during a language experiment for a participant with MISViS in the absence of migraine compared to controls.
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Certain patterns can induce perceptual illusions/distortions and visual discomfort in most people, headaches in patients with migraine, and seizures in patients with photosensitive epilepsy. Visual stimuli are common triggers for migraine attacks, possibly because of a hyperexcitability of the visual cortex shown in patients with migraine. Precision ophthalmic tints (POTs) are claimed to reduce perceptual distortions and visual discomfort and to prevent migraine headaches in some patients. We report an fMRI visual cortical activation study designed to investigate neurological mechanisms for the beneficial effects of POTs in migraine. Eleven migraineurs and 11 age- and sex-matched non-headache controls participated in the study using non-stressful and stressful striped patterns viewed through gray, POT, and control coloured lenses. For all lenses, controls and migraineurs did not differ in their response to the non-stressful patterns. When the migraineurs wore gray lenses or control coloured lenses, the stressful pattern resulted in activation that was greater than in the controls. There was also an absence of the characteristic low-pass spatial frequency (SF) tuning in extrastriate visual areas. When POTs were worn, however, both cortical activation and SF tuning were normalized. Both when observing the stressful pattern and under more typical viewing conditions, the POTs reduced visual discomfort more than either of the other two lenses. The normalization of cortical activation and SF tuning in the migraineurs by POTs suggests a neurological basis for the therapeutic effect of these lenses in reducing visual cortical hyperactivation in migraine.
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Several behavioral studies have shown that developmental dyslexics do poorly in tests requiring rapid visual processing. In primates fast, low-contrast visual information is carried by the magnocellular subdivision of the visual pathway, and slow, high-contrast information is carried by the parvocellular division. In this study, we found that dyslexic subjects showed diminished visually evoked potentials to rapid, low-contrast stimuli but normal responses to slow or high-contrast stimuli. The abnormalities in the dyslexic subjects' evoked potentials were consistent with a defect in the magnocellular pathway at the level of visual area 1 or earlier. We then compared the lateral geniculate nuclei from five dyslexic brains to five control brains and found abnormalities in the magnocellular, but not the parvocellular, layers. Studies using auditory and somatosensory tests have shown that dyslexics do poorly in these modalities only when the tests require rapid discriminations. We therefore hypothesize that many cortical systems are similarly divided into a fast and a slow subdivision and that dyslexia specifically affects the fast subdivisions.
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Developmental dyslexics often complain that small letters appear to blur and move around when they are trying to read. Anatomical, electrophysiological, psychophysical and brain-imaging studies have all contributed to elucidating the functional organization of these and other visual confusions. They emerge not from damage to a single visual relay but from abnormalities of the magnocellular component of the visual system, which is specialized for processing fast temporal information. The m-stream culminates in the posterior parietal cortex, which plays an important role in guiding visual attention. The evidence is consistent with an increasingly sophisticated account of dyslexia that does not single out either phonological, or visual or motor deficits. Rather, temporal processing in all three systems seems to be impaired. Dyslexics may be unable to process fast incoming sensory information adequately in any domain.
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This investigation examines the question of whether decreasing wavelength of light and/or reducing luminance benefits oculomotor efficiency in normal and reading disabled (RD) children. Two groups of children were identified as normal or disabled readers using standardized reading tests. After suitable practice, eye movements were objectively measured with the Visagraph II as each of the subjects silently read a series of three different selections at their independent reading level with clear (control), gray, and blue filters. Four variables were measured for each subject. Data were analyzed using a repeated measure ANOVA and post hoc tests. The standardized reading tests significantly differentiated average from poor readers using grade scores and percentiles. Initially, with clear filters, eye movement scores of normal readers were superior to disabled readers for fixations regressions, and rate of reading. Among the RDs--but not the normals--the three variables improved with the blue filter when compared with the clear filter, number of fixations and regressions were significantly lower, and rate was significantly higher. Gray filters yielded no significant changes. Improvement with the blue filters normalized the three variables in that there were no significant differences between normal and disabled readers. This investigation confirms a link between wavelength of light and eye movement efficiency in reading. Blue filters resulted in a significant improvement in the number of fixations and regressions and rate of reading in RD children. The outcome broadens the concept of transient system deficit established in previous research to include the effect on oculomotor efficiency. The educational implications of this study are of special interest to optometrists.
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Low literacy is termed 'developmental dyslexia' when reading is significantly behind that expected from the intelligence quotient (IQ) in the presence of other symptoms--incoordination, left-right confusions, poor sequencing--that characterize it as a neurological syndrome. 5-10% of children, particularly boys, are found to be dyslexic. Reading requires the acquisition of good orthographic skills for recognising the visual form of words which allows one to access their meaning directly. It also requires the development of good phonological skills for sounding out unfamiliar words using knowledge of letter sound conversion rules. In the dyslexic brain, temporoparietal language areas on the two sides are symmetrical without the normal left-sided advantage. Also brain 'warts' (ectopias) are found, particularly clustered round the left temporoparietal language areas. The visual magnocellular system is responsible for timing visual events when reading. It therefore signals any visual motion that occurs if unintended movements lead to images moving off the fovea ('retinal slip'). These signals are then used to bring the eyes back on target. Thus, sensitivity to visual motion seems to help determine how well orthographic skill can develop in both good and bad readers. In dyslexics, the development of the visual magnocellular system is impaired: development of the magnocellular layers of the dyslexic lateral geniculate nucleus (LGN) is abnormal; their motion sensitivity is reduced; many dyslexics show unsteady binocular fixation; hence poor visual localization, particularly on the left side (left neglect). Dyslexics' binocular instability and visual perceptual instability, therefore, can cause the letters they are trying to read to appear to move around and cross over each other. Hence, blanking one eye (monocular occlusion) can improve reading. Thus, good magnocellular function is essential for high motion sensitivity and stable binocular fixation, hence proper development of orthographic skills. Many dyslexics also have auditory/phonological problems. Distinguishing letter sounds depends on picking up the changes in sound frequency and amplitude that characterize them. Thus, high frequency (FM) and amplitude modulation (AM) sensitivity helps the development of good phonological skill, and low sensitivity impedes the acquisition of these skills. Thus dyslexics' sensitivity to FM and AM is significantly lower than that of good readers and this explains their problems with phonology. The cerebellum is the head ganglion of magnocellular systems; it contributes to binocular fixation and to inner speech for sounding out words, and it is clearly defective in dyslexics. Thus, there is evidence that most reading problems have a fundamental sensorimotor cause. But why do magnocellular systems fail to develop properly? There is a clear genetic basis for impaired development of magnocells throughout the brain. The best understood linkage is to the region of the Major Histocompatibility Complex (MHC) Class 1 on the short arm of chromosome 6 which helps to control the production of antibodies. The development of magnocells may be impaired by autoantibodies affecting the developing brain. Magnocells also need high amounts of polyunsaturated fatty acids to preserve the membrane flexibility that permits the rapid conformational changes of channel proteins which underlie their transient sensitivity. But the genes that underlie magnocellular weakness would not be so common unless there were compensating advantages to dyslexia. In developmental dyslexics there may be heightened development of parvocellular systems that underlie their holistic, artistic, 'seeing the whole picture' and entrepreneurial talents.
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In two studies, the first in a school in Peterborough and the second in a school in Norwich, more than 233 children aged 8-12 years received either an orthoptic examination, or an optometric examination, together with an examination using coloured overlays and a test of reading fluency. In both studies more than one-third of the children reported visual symptoms. More than one-third of the children chose to use an overlay, and they read more quickly with it than without. The colour of the overlay chosen was weakly related to the binocular amplitude of accommodation: overlays reflecting greater energy at long wavelengths were chosen more frequently by children with a higher amplitude of accommodation. Although the visual symptoms were strongly related to the use of an overlay, in neither study was the benefit from an overlay strongly related to the orthoptic or optometric findings. Nevertheless, children who used an overlay had slightly, but significantly, reduced mean binocular amplitude of accommodation and fusional reserves. On average, children with 'sensory' or 'motor' instability of the nonius strips of the Mallett unit read more slowly than others, as did those with poor stereopsis. However, 60% of those demonstrating sustained overlay use gave a normal response on the Mallett aligning prism test, compared with 80% of those who did not use an overlay for a sustained period. Another indicator of decompensated heterophoria, Sheard's criterion, did not differentiate subjects who used overlays from those who did not. Although binocular and accommodative anomalies do not appear to be the underlying mechanism for the benefit from coloured filters in most cases, there may be some individuals who respond to coloured filters and in whom these ocular motor factors require treatment. Children with visually precipitated symptoms and/or reading difficulties need both a careful evaluation of their accommodative and binocular status, and an investigation of the effect of coloured filters.
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The magnocellular system plays an important role in visual motion processing, controlling vergence eye movements, and in reading. Yellow filters may boost magnocellular activity by eliminating inhibitory blue input to this pathway. It was found that wearing yellow filters increased motion sensitivity, convergence, and accommodation in many children with reading difficulties, both immediately and after three months using the filters. Motion sensitivity was not increased using control neutral density filters. Moreover, reading-impaired children showed significant gains in reading ability after three months wearing the filters compared with those who had used a placebo. It was concluded that yellow filters can improve magnocellular function permanently. Hence, they should be considered as an alternative to corrective lenses, prisms, or exercises for treating poor convergence and accommodation, and also as an aid for children with reading problems.
Article
Some individuals with dyslexia demonstrate deficits in reading, visual attention, and visual processing which can be attributed to a functional failure of the magnocells in the visual system or in the dorsal visual pathway. The study examines the role of magno/dorsal function in dyslexic adults compared with normal, illiterate, and semi‐literate readers. Coherent motion and coherent form were used in Experiment 1, and the frequency doubling illusion and static‐gratings were used in Experiment 2. If a magno/dorsal deficit is demonstrated for dyslexic readers but not illiterate, semi‐literate, and normal reading adults, then the deficit cannot be attributed to reading experience. Illiterate adults performed the same as normal and semi‐literate readers in coherent motion and frequency doubling tasks, and all three groups performed better than the dyslexic readers. There was no difference between any of the groups in the coherent form or static grating tasks. Together, these studies show that illiterate and semi‐literate adults do not demonstrate a magno/dorsal deficit that is a characteristic of some sufferers of dyslexia. Therefore, magno/dorsal deficits in dyslexia are unlikely to be a consequence of failing to learn to read but rather provides evidence to suggest a causal role for reduced visual magno/dorsal processing.
Article
Some people doubt that the concept of developmental dyslexia (DD) is useful at all because the phonological weaknesses seen in DD cannot be distinguished from those found in every person with poor reading skills, whatever their cause. Here I argue that true DD is characterized by poor temporal processing, hence impaired visual and auditory sequencing, that is caused by impaired development of transient/magnocellular (M-) systems throughout the brain. These deficits can be measured to distinguish the causes of the phonological weaknesses in DD from those causing similar deficits in other types of poor reading; Importantly this knowledge can be exploited to develop effective improvements in treatment. The evidence for impaired visual magnocellular function in many, if not all, people with dyslexia is now overwhelming; it is supported not only by psychophysical tests of M- function, but also by electrophysiological, eye movement, attentional, imaging, interventional and genetic findings. Analogously, auditory temporal processing is mediated by auditory transient, "magnocellular', processing systems, and evidence is accumulating persuasively that this system is also impaired in dyslexics. I briefly introduce the idea that 'motor magnocellular systems' may also be impaired in dyslexia, then consider genetic, immunological and nutritional factors that interact to cause the impaired magnocellular phenotype. I then discuss why the dyslexic phenotype is so common by speculating about what strengths it might confer that would maintain the responsible genes in the human genome.
Article
Claims that coloured filters aid reading date back 200 years and remain controversial. Some claims, for example, that more than 10% of the general population and 50% of people with dyslexia would benefit from coloured filters lack sound evidence and face validity. Publications with such claims typically cite research using methods that have not been described in the scientific literature and lack a sound aetiological framework. Notwithstanding these criticisms, some researchers have used more rigorous selection criteria and methods of prescribing coloured filters that were developed at a UK Medical Research Council unit and which have been fully described in the scientific literature. We review this research and disconfirm many of the more extreme claims surrounding this topic. This literature indicates that a minority subset of dyslexics (circa 20%) may have a condition described as visual stress which most likely results from a hyperexcitability of the visual cortex. Visual stress is characterised by symptoms of visual perceptual distortions, headaches, and eyestrain when viewing repetitive patterns, including lines of text. This review indicates that visual stress is distinct from, although sometimes co-occurs with, dyslexia. Individually prescribed coloured filters have been shown to improve reading performance in people with visual stress, but are unlikely to influence the phonological and memory deficits associated with dyslexia and therefore are not a treatment for dyslexia. This review concludes that larger and rigorous randomised controlled trials of interventions for visual stress are required. Improvements in the diagnosis of the condition are also a priority.
Article
Photophobia, an abnormal intolerance to light, is associated with a number of ophthalmic and neurologic conditions. In the presence of normal neurologic and ophthalmologic examinations, the most common conditions associated with photophobia are migraine, blepharospasm, and traumatic brain injury. Recent evidence indicates that the intrinsically photosensitive retinal ganglion cells play a key role in the pathophysiology of photophobia. Although pharmacologic manipulation of intrinsically photosensitive retinal ganglion cells and the neural pathways that mediate photophobia may be possible in the future, current therapies are directed at the underlying cause of the photophobia and optical modulation of these cells and pathways.
Article
A number of studies have shown that students experiencing specific reading disabilities have processing deficits related to their visual system. The transient system, which is responsible for motion detection and transient‐on‐sustained inhibition, is sluggish. This research project manipulated colour and contrast for a rate of reading task and showed that students with a transient processing problem process information differently whether they are normal or disabled readers. Short wavelengths (blue) and low contrast have been shown to balance the relative processing of the transient and sustained systems on visual, perceptual and some reading tasks. This study adds support for the use of these techniques to enable students with transient processing problems to increase their rate of reading.
Article
Meares-Irlen Syndrome (MIS) is characterised by symptoms of visual stress and visual perceptual distortions that are alleviated by using individually prescribed coloured filters. Coloured overlays (sheets of transparent plastic that are placed upon the page) are used to screen for the condition. MIS is diagnosed on the basis of either the sustained voluntary use of an overlay or an immediate improvement (typically of more than 5%) on the Wilkins Rate of Reading Test (WRRT). Various studies are reviewed suggesting a prevalence of 20–34% using these criteria. Stricter criteria give a lower prevalence: for example, 5% of the population read more than 25% faster with an overlay. It has been alleged that MIS is more common in dyslexia, but this has not been systematically investigated. We compared a group of 32 dyslexic with 32 control children aged 7–12 years, matched for age, gender and socio-economic background. Participants were tested with Intuitive Overlays, and those demonstrating a preference had their rate of reading tested using the WRRT with and without their preferred overlay. Both groups read faster with the overlay, and more so in the dyslexic group. ANOVA revealed no significant effect of group, but a significant improvement in WRRT with overlay (p=0.009) and a significant interaction between group and overlay (p=0.031). We found a similar prevalence of MIS in the general population to that in previous studies and a prevalence in the dyslexic group that was a little higher (odds ratio for >5% criterion: 2.6, 95% confidence limit 0.9–7.3). The difference in prevalence in the two groups did not reach statistical significance. We conclude that MIS is prevalent in the general population and possibly a little more common in dyslexia. Children with dyslexia seem to benefit more from coloured overlays than non-dyslexic children. MIS and dyslexia are separate entities and are detected and treated in different ways. If a child has both problems then they are likely to be markedly disadvantaged and they should receive prompt treatments appropriate to the two conditions. It is recommended that education professionals as well as eye-care professionals are alert to the symptoms of MIS and that children are screened for this condition, as well as for other visual anomalies.
Article
Photophobia is an abnormal sensitivity to light experienced by migraineurs during attacks. The pathophysiology of photophobia is poorly understood. Nevertheless, 2 facts appear to have a link with photophobia: visual cortex hyperexcitability on the one hand and interactions between visual pathway and trigeminal nociception on the other. We used H(2)(15)O PET to study photophobia induced by continuous luminous stimulation covering the whole visual field in 8 migraineurs during spontaneous migraine attacks, after headache relief by sumatriptan and during attack-free interval. The intensity of the luminous stimulation provoking photophobia with subsequent headache enhancement was specifically determined for each patient. We found that low luminous stimulation (median of 240 Cd/m(2)) activated the visual cortex during migraine attacks and after headache relief but not during the attack-free interval. The visual cortex activation was statistically stronger during migraine headache than after pain relief. These findings suggest that ictal photophobia is linked with a visual cortex hyperexcitability. The mechanism of this cortical hyperexcitability could not be explained only by trigeminal nociception because it persisted after headache relief. We hypothesize that modulation of cortical excitability during migraine attack could be under brainstem nuclei control.
Article
The magnitudes of metacontrast masking and of stroboscopic motion were investigated as a function of the color of isoluminant backgrounds on which the stimuli consisting of rectangular-shaped luminance decrements appeared. White, green, and red backgrounds were employed. Background isoluminance was obtained by minimal flicker settings with heterochromatic flicker of uniform fields. Both metacontrast and stroboscopic motion were decreased when red as compared to white or green backgrounds were used. Within the context of current sustained-transient channel approaches to visual masking and motion, these results indicate that the activity of transient channels is attenuated by red relative to white or green backgrounds. Moreover, these psychophysical findings may correspond to the suppressive effects of diffuse red light on neural activity in the transient M pathway of monkey.
Article
Many reports suggest that the majority of dyslexic children have a measurable disorder of the fast processing pathway of the visual system. This pathway is believed to extend from the retina to the occipital and parietal areas of the brain, and is referred to as the magnocellular (M) or transient pathway. Evidence in support of the magnocellular deficit theory comes from several sources, but is not totally consistent. Histological studies have revealed shrinkage and disorganisation of M cells in the lateral geniculate nucleus of dyslexic subjects. Psychophysical investigations of visual persistence, contrast sensitivity to moving sine wave gratings and flicker sensitivity, report atypical results in dyslexic children, reflecting an apparent deficiency in the transient system, although not all psychophysical studies have demonstrated such a deficiency. Visual evoked potential responses to a wide range of stimuli have been reported to be deficient in dyslexic subjects, but again there are dissenting papers. These reports have been subject to critical review and analysis, new techniques specifically to stimulate the magnocellular pathway are described, and the relevance of this research to tinted lens therapies and clinical reading problems is discussed.
Article
The contribution of M(y)-cell activity within a framework of a magnocellular-deficit theory of dyslexia is currently unknown. Twenty-one dyslexic readers and 19 control readers were compared on their threshold detection for the frequency doubling illusion - an index of M(y)-cell activity, coherent motion, and a visual acuity task. The dyslexic group performed more poorly on detection of the frequency doubling illusion and coherent motion compared to the control group, but both groups performed comparably on the visual acuity task. The results from this study indicate that if a magno deficit exists in dyslexia, it may originate at a retinal level at least partly mediated by M(y)-cell abnormalities.
Article
A review of the neurophysiological literature suggests that the magnocellular pathway has adequate spatial-frequency and contrast sensitivity to perceive text under normal contrast conditions (>10%) and also is suppressed by red light. Results from three experiments involving color and reading show that red light impairs reading performance under normal luminance contrast conditions. However in a fourth experiment, isoluminant color text, designed to selectively activate the parvocellular pathway, is easier to read under red light. These discrepant results suggest that the magnocellular pathway is the dominant visual pathway for text perception. Implications for reading models and developmental dyslexia are discussed.
Article
Reading is more difficult than speaking because an arbitrary set of visual symbols must be rapidly identified, ordered and translated into the sounds they represent. Many poor readers have particular problems with the rapid visual processing required for these tasks because they have a mild impairment of the visual magnocellular system. This deficit has been demonstrated using neuropathological, evoked potential, functional magnetic resonance imaging and psychophysical techniques. The sensitivity of the M-system in both good and bad readers correlates with their orthographic abilities, suggesting that the M-system plays an important part in their development. This role is probably to mediate steady direction of visual attention and eye fixations on words. Thus many children with reading difficulties have unsteady eye control and this causes the letters they are trying to read to appear to move around, so that they cannot tell what order they are meant to be in. Therefore, boosting M-performance using yellow filters, or training eye fixation, can improve reading performance very significantly. Several genetic linkage studies have associated reading difficulties with the MHC control region on the short arm of chromosome 6. This system has recently been shown to help regulate the differentiation of M-cells. This association could also explain the high incidence of autoimmune conditions in poor readers. Other chromosomal sites are associated with the metabolism of polyunsaturated fatty acids (PUFAs) as found in fish oils, and this could explain why PUFA supplements can improve reading.
Aprendizagem e Leitura -Síndrome de Irlen
  • M R Guimarães
  • I R Guimarães
Guimarães, M. R., & Guimarães, I. R. Aprendizagem e Leitura -Síndrome de Irlen. In O. Z. M. de Assis. (Org.). Neurociências e Educação. (vol. 1, p. 175-186). Campinas, SP: Book Editora.
Selective spectral filters in the treatment of visually induced headaches and migraines: a clinical study of 93 patients
  • M R Guimarães
  • J R Guimarães
  • R Q Guimarães
  • M R V Nogueira
  • M R Botelho
  • M E A Guimarães
Guimarães, M. R., Guimarães, J. R., Guimarães, R. Q., Nogueira, M. R. V., Botelho, M. R., & Guimarães, M. E. A. (2010). Selective spectral filters in the treatment of visually induced headaches and migraines: a clinical study of 93 patients. Headache Medicine, 1(2), 72.