Purpose: There is little agreement on the age at which visual acuity (VA) and contrast sensitivity (CS) become adult-like. The ultimate purpose of this thesis was to determine whether VA and CS are adult-like at the age of 6-8 or 9-12 years by using both objective and subjective methods in the same individuals. The objective method (sweep visually evoked potentials [sVEP]) has many parameters that may affect the measurement of VA or CS and previously these had not been studied systematically, especially in children. Therefore, a second purpose was to study the effects of these parameters on VA and contrast thresholds and to determine the parameters that give the most repeatable measurements and the greatest number of viable readings in children, to be compared to previous data obtained in adults. Methods: The effect of five criteria (C0-C4) for choosing the endpoint for the regression line fitting and three luminance levels (25, 50, and 100 cd/m2) on the sVEP VA and contrast thresholds (at 1 and 8 cpd) was investigated in six 6-8 year old children. Additionally, the effect of these parameters on the number of viable readings obtained from five active electrodes was investigated. C0 was derived from the sVEP software (PowerDiva), C1 used the best fit by eye to determine the range over which the regression line was fitted, C2 used the data point between signal peak and the last data point with an SNR ≥ 1, C3 was similar to C2 but was defined so that the threshold should be within the sweep range, and C4 was similar to C2 except that the SNR should not fall below one at any point within the range used for the regression line fitting. The effects of two electrode placements, three temporal frequencies (6, 7.5, and 10 Hz), sweep direction (low to high and high to low), presence or absence of a fixation target, three stimulus areas (6, 4, and 2° for VA and 15, 10, and 6° for contrast thresholds) and three sweep durations (10, 15, and 20 sec) on VA and contrast thresholds (at 1, 4, or 8 cpd) measured with sVEP were also investigated in six 6-8 year-old children and six adults with normal vision. Additionally, the effect of these parameters on the number of viable readings obtained from five active electrodes was investigated. The sVEP parameters that were found to give the best threshold measurements were employed in a cross sectional study of the development of VA and CS. In this study the objective sVEP technique and two psychophysical techniques were used. The psychophysical techniques were comprised of a two-alternative forced choice (2AFC) staircase for measuring VA and contrast thresholds and signal detection theory (SDT) for measuring contrast threshold. Crowded and uncrowded logMAR VA were also measured with a Bailey-Lovie logMAR chart. The study included three age groups (6-8, 9-12 year olds and adults). The criterion employed by each age group as indicated by the SDT was compared. Results: There was a significant effect of the criterion for choosing the endpoint for the regression line fitting (p < 0.05) on all the measures and a significant effect of luminance (p = 0.036) on contrast threshold at 1 cpd. Criterion C2 (in which the range for the regression line fit was defined to include all the data between the signal peak and the last data point [furthest from the peak] with an SNR ≥ 1) consistently gave more viable readings and better thresholds (i.e. higher VA and lower contrast thresholds) than the other criteria. Also C2 was the best criterion in terms of repeatability in children, and repeatability and validity in adults (Yadav et al., 2009). The luminance of 25 cd/m2 gave higher contrast thresholds than 50 or 100 cd/m2. There was a significant effect of temporal frequency on the number of viable readings for VA (p < 0.0001) and for contrast thresholds (p = 0.0001), with more viable readings at 7.5 Hz than at either 6 or 10 Hz. The adults gave more readings with the fixation target than without it (p = 0.04) for contrast threshold at 1 cpd. The smallest stimulus area used gave rise to fewer viable readings in both adults and children (p = 0.022 for VA and 0.0001 for contrast threshold). The other parameters (electrode placement, sweep direction and sweep duration) did not result in significant differences. There was a significant effect of age on crowded (p = 0.0001) and uncrowded (p < 0.0001) VA. The 6-8 year olds gave poorer VA than the 9-12 year olds or adults for both crowded and uncrowded VA. For the grating VA (sVEP and 2AFC staircase) there was a significant effect of age (p = 0.002). The 6-8 year olds had poorer VA than the 9-12 year olds or adults. For contrast threshold at 1 cpd, a significant effect of age was found for the 2AFC (p = 0.008) and SDT (p = 0.0003). The 6-8 year olds gave poorer contrast thresholds than adults with each procedure. For contrast thresholds at 8 cpd, there was a significant effect of age with the 2AFC staircase (p = 0.036). The 6-8 year olds gave poorer contrast thresholds than the 9-12 year olds. For SDT, there was a significant effect of age on criterion (p < 0.05), with adults being more likely to say “no” in the yes-no SDT procedure than both the 6-8 year olds and the 9-12 year olds for contrast threshold at 1 cpd. Adults were also more likely to say “no” than the 9-12 year olds for contrast thresholds at 8 cpd. Conclusions: This thesis has shown that VA and CS are not adult-like until the age of 9-12 years by these measures and that children do show differences in criterion compared to adults in psychophysical testing. This difference in criterion indicates the use of SDT or force-choice procedures to avoid this problem in any psychophysical developmental study. It has also shown that criterion for choosing the endpoint for the regression line fitting in the sVEP technique has the greatest effect on VA and contrast thresholds measurements and viable readings, while the other sVEP parameters have little effect on the thresholds.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 56-62). Also available via the Internet.

Thesis (Ph.D.) - University of Queensland, 2006. / Includes bibliography.

O estudo da acuidade Vernier (VRN) revela a capacidade do sistema visual humano em detectar deslocamentos espaciais de poucos arcos de segundos, menores que a distância entre dois cones foveais adjacentes. Tal fato desperta interesse teórico sobre o tema, além de futuras aplicações na área clínica. A acuidade VRN pode ser medida tanto psicofisicamente quanto eletrofisiologicamente. Para a detecção de quebras de colinearidade (acuidade VRN), alguns autores hipotetizam que as células ganglionares (CGs) M da retina provêem sinal adequado da retina ao córtex, e dão suporte ao desempenho psicofísico da tarefa VRN. Em condições de estímulos semelhantes, as células ganglionares magnocelulares (M) em primatas parecem ter precisão espacial com razão sinal-ruído mais alta do que as células parvocelulares (P) . A dependência ao contraste (C) das células M na precisão espacial, frequência espacial, frequência temporal e velocidade do estímulo é mais similar ao desempenho psicofísico em humanos do que comparados aos dados das células P (Rüttiger et al., 2002; Sun et al., 2004). Nós utilizamos o Potencial Provocado Cortical Visual de Varredura (sVEP) para avaliar esta hipótese no nível de processamento intermediário entre as respostas de célula única na retina e a detecção psicofísica. Nós medimos os limiares corticais VRN em função do contraste (14 participantes, média de 28,21 ± 2,8) e lacunas (9 participantes, média de 29,7 ± 5,9). As quebras verticais VRN na colinearidade foram introduzidas em uma grade de onda quadrada horizontal. O estímulo VRN alternou entre um estado alinhado (grades sem quebras) e desalinhado (grades com quebras) a 6 Hz. Durante cada uma das 10 tentativas, o deslocamento aumentou em passos logarítmicos iguais de 0,5 a 7,5. O limiar VRN foi definido no momento do deslocamento em que a extrapolação linear da média vetorial das respostas em 1F atinge zero uV. Os contrastes testados foram: 4, 8, 16, 32, 64, 80%. Os resultados mostram que (1) aos limiares VRN em Log, medidos com sVEP, com o C em Log, diminuíram de forma linear (com uma inclinação de -0,5), similiares às células ganglionares M mas não P (Sun et al., 2004) e próximo às medidas psicofísicas (Sun et al., 2004; Wehrhahn e Westheimer, 1990); (2) Para C 16% obtivemos limiares de hiperacuidade (menor que 1 arcmin). Em altos contrastes a média do limiar foi de 0,37(erro padrão de 0,06 unidades logarítmicas); (3) Os limiares para o 2F tiveram uma dependência para o contraste diferente, com poucos efeitos para contraste abaixo de 16%. (4) As inclinações das linhas de extrapolação dos sVEP para o 1F1 foram 2 a 3 vezes maiores que as inclinações para 2F; (5) No protocolo controle, deslocamentos bidirecionais e simétricos geraram somente respostas no 2F. Os resultados 3 a 5 implicam que os componentes 1F e 2F derivam de neurônios distintos e fundamentam que respostas no 2F refletem respostas de movimento cortical simétrico. A dependência dos limiares de contraste do sVEP VRN (1F) é similiar aos estudos prévios psicofísicos (Sun et al., 2004; Wehrhahn e Westheimer, 1990), e repete a dependência ao contraste das células M (Sun et al., 2004). Estes resultados fundamentam a hipótese que o córtex extrai informações da posição relativa com precisão de hiperacuidade dos sinais advindos das células M / The human visual system is able to detect spatial displacements of a few arcsec, much smaller than the distance between two adjacent foveal cones. Hyperacuity tasks such as Vernier (VRN) have both theoretical importance as well as clinical application. VRN can be measured psychophysically and with sVEP. Some authors hypothesize that M ganglion cells provide the retinal signal to cortex adequate to support Vernier performance. Under stimulus conditions analogous to detection of Vernier offsets, primate magnocellular (M) ganglion cells appear to have more precise spatial localization (with higher Signal to Noise Ratio) than parvocellular (P) cells, and the dependence of M cell spatial precision on contrast (C), spatial frequency, temporal frequency and stimulus velocity is more similar to human psychophysical performance than comparable data from P cells (Ruttiger et al, 2002; Sun et al., 2003, 2004) (Rüttiger et al., 2002; Sun et al., 2004). We measured the C-dependence of cortical VRN thresholds (thd) using the Sweep VEP (sVEP) to help evaluate this hypothesis at a processing level intermediate between single-cell retinal responses and psychophysical detection. We measured Vernier thds using sVEP as function of constrast (12 young adults, age means 28.21 yrs ± 2.8) and Gaps (9 participants, 29.7 ± 5.9) with normal vision. Vertical VRN breaks in colinearity were introduced to a horizontal squarewave grating. The VRN stimulus alternated between aligned (grating w/o breaks) and misaligned (w/breaks) states at 6 (or 10) Hz. During each of ten, 10-s trials, displacement (D) was increased in equal logarithmic steps from 0.5 to 7.5. Vernier thd was defined as the D at which the rising slope of the vector averaged 1F response extrapolated to zero V. The Cs tested were: 4, 8, 16, 32, 64, 80%. We Found: (1) Log Vernier thd measuered with sVEP decreased linearly with log C similar to M- (but not P-) ganglion cells (Sun et al., 2004) with a slope of -0.5, close to that measured psychophysically (Rüttiger et al., 2002; Sun et al., 2004); (2) For C 16% , thds were true hyperacuities (less than 1). At high C, mean thd was 0.37(S.E = 0.06 log units); (3) Thds for 2F had a different C dependence, with little effect of C below 16 %. Thds for 2F were < 1F thds below 16 % C, but were 1F thds beyond 16 %; (4) The slopes of the sVEP extrapolation lines for 1F were 2-3 times > 2F slopes; (5) In a control protocol, symmetric, bidirectional displacements only generated 2F responses. Results 3-5 imply that the 1F and 2F components derive from distinct neurons, and support the notion that 2F responses reflect symmetric cortical motion responses. The C-dependence of sVEP Vernier (1F) thresholds is similar to prior psychophysics (Sun et al., 2004; Wehrhahn e Westheimer, 1990), and recapitulates Mcell C-dependence (Sun et al., 2004). This results support the hypothesis that cortex extracts relative position information with hyperacuity precision preferentially from M cell signals

SALES, R. Achados da acuidade visual estática e dinâmica em pacientes com disfunção vestibular. 106f. Tese (Doutorado) da Faculdade de Medicina de Ribeirão Preto-USP. Ribeirão Preto-SP, 2013. Para a obtenção da visão nítida é necessário que a imagem permaneça estável na retina, mesmo com a movimentação cefálica. As pessoas que sofrem de labirintopatias são mais sensíveis a efeitos visuais, podendo apresentar os sintomas de tontura, enjoo e oscilopsia durante a movimentação cefálica. Esse fato ocorre devido ao conflito sensorial entre o sistema vestibular e visual. O presente estudo objetivou verificar a variação da acuidade visual estática e dinâmica em pacientes com disfunção vestibular. Foram selecionados pacientes de ambos os sexos, com idade entre 14 e 88 anos de idade submetidos ao exame de vetoeletronistagmografia entre os anos de 2009 e 2011. Esses pacientes também foram submetidos ao exame de acuidade visual estática e dinâmica. Na acuidade visual dinâmica, foram pré-determinadas frequências de 0.5, 1.0, 1.5 e 2.0 Hertz para a movimentação cefálica. Os resultados mostraram maior decréscimo da acuidade visual estática e dinâmica entre os pacientes com labirintopatias bilaterais se comparadas com as unilaterais e o grupo controle. Além disso, o aumento da frequência produziu decréscimo da acuidade visual em todos os grupos e a posição da movimentação cefálica na vertical mostrou maior sensibilidade se comparada à horizontal. Pôde-se concluir que os pacientes com labirintopatias apresentaram decréscimo da acuidade visual estática e dinâmica, principalmente nas frequências mais altas e com a movimentação cefálica na posição vertical, sendo esses exames importantes para auxiliar no diagnóstico e monitoramento das labirintopatias. Palavras-chave: Acuidade visual; Sistema vestibular / For obtaining an accurate image is necessary that remains stable on the retina, even with head movement. People suffering from labyrinthopathy are more sensitive to visual effects, and may have symptoms of dizziness, nausea and oscillopsia during head movement. This fact occurs because the sensory conflict between visual and vestibular system. The present study aimed to determine the variation of static and dynamic visual acuity in patients with vestibular dysfunction. Selected patients were of both gender, aged between 14 and 88 years old who underwent examination vetoeletronistagmografia between the years 2009 and 2011 at the home Institution. The patients were subjected to tests of visual acuity static and dynamic. In dynamic visual acuity, were predetermined frequencies of 0.5, 1.0, 1.5 and 2.0 Hz for the patient\'s head movement. The results showed a greater decrease in static and dynamic visual acuity among patients with bilateral labyrinthopathy compared with the unilateral and control groups. In addition, the frequency increase produced decreased visual acuity in all groups and the position of head movement in the vertical showed a higher sensitivity compared to the horizontal. It was concluded that patients with labyrinthopathy showed a decrease of static and dynamic visual acuity, especially at higher frequencies and with head movement in a vertical position, and these important tests to assist in diagnosis and monitoring of the labyrinthopathy. Keywords: Visual acuity; Vestibular system

Orientador: Carlos Eduardo Leite Arieta / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-23T07:26:52Z (GMT). No. of bitstreams: 1 Bisneto_OtavioSiqueira_D.pdf: 1957765 bytes, checksum: 2b131f1ff863d58643b8b214c93cb0cf (MD5) Previous issue date: 2013 / Resumo: Objetivo: avaliar os resultados clínicos e possíveis complicações do implante da lente intraocular (LIO) Sulcoflex® Multifocal. Material e Método: realizou-se estudo tipo série de casos de indivíduos submetidos ao implante bilateral da LIO Sulcoflex® Multifocal no Hospital de Olhos do Paraná (Curitiba - Brasil). Foram incluídos indivíduos previamente operados de catarata, submetidos ao implante bilateral da LIO Sulcoflex® Multifocal, no período de julho de 2010 a janeiro de 2012, sendo os principais critérios de inclusão presença de LIO monofocal não acomodativa implantada no saco capsular de ambos os olhos e acuidade visual corrigida ou não de 20/25 ou melhor em ambos os olhos e os principais critérios de exclusão presença de doença ocular associada e refração cilíndrica maior que 0,75 D negativa ou esférica maior que 3 D positivas ou negativas. Foram estudadas as seguintes variáveis: acuidade visual para longe e para perto com e sem correção óptica; grau de refração esféro-cilíndrica; pressão intraocular; contagem de células endoteliais; aberrações ópticas de alta ordem; sensibilidade ao contraste e complicações intra e pós-operatórias. Todas as cirurgias foram realizadas pelo mesmo cirurgião, sob anestesia tópica, com implante da LIO por incisão de 2,75mm, objetivando se a emetropia. Resultados: foram avaliados 16 olhos de 8 indivíduos. A idade média foi de 63.87±7,1 anos variando de 55 a 79 anos. O tempo médio de seguimento foi de 11,37 +- 1,4 meses variando de 10 a 14 meses. Houve piora de 1 linha da acuidade visual para longe sem correção óptica em 7 olhos (43,7%), e melhora da acuidade visual de perto com todos os olhos apresentando J2 ou melhor sem correção óptica. Conclusão: após o implante da LIO Sulcoflex® Multifocal houve melhora da acuidade visual de perto sem correção óptica, e diminuição da acuidade visual de longe com e sem correção óptica, e da sensibilidade ao contraste em 2 das 5 frequências espaciais estudadas. A abertura invertida (face anterior voltada posteriormente) de uma lente no momento do implante ocasionou perda significativa de células endoteliais neste olho / Abstract: Purpose: to evaluate the clinical results and possible complications of the Sulcoflex® Multifocal intraocular lens implantation. Methods: It was conducted a case series study of patients undergoing IOL Sulcoflex® Multifocal bilateral implantation at Paraná Eye Hospital (Curitiba - Brazil). It were included patients previously operated for cataract, underwent bilateral implantation of IOL Sulcoflex® Multifocal, from July 2010 to January 2012, being the main inclusion criteria, presence of monofocal no accommodative IOL implanted in capsular bag in both eyes and best corrected or not visual acuity 20/25 or better in both eyes; the main exclusion criterias were presence of eye disease, cylindrical refraction greater than -0.75 diopters or greater than 3 positive or negative spherical diopters. It were studied the following variables: visual acuity for near and distance vision with and without optical correction; degree of sphero-cylindrical refraction, intraocular pressure, endothelial cell count, high-order aberrations, contrast sensitivity and intra and postoperative complications. All surgeries were performed by the same surgeon, under topical anesthesia with IOL implant incision by 2.75 mm, with the target of emmetropia. Results: It was evaluated 16 eyes of 8 persons. The mean age was 63,87 +- 7,1 years, ranging from 55 to 79 years. The mean follow up was 11,37 +- 1,4 months, ranging from 10 to 14 months. It was observed decreased of 1 line in distance visual acuity without correction in 7 eyes (43,7%), and improvement of near visual acuity, with all eyes J2 or better without correction. Conclusion: after Sulcoflex® Multifocal IOL implantation, the near vision without correction was improved, the far vision with and without correction was decreased, and contrast sensitivity was decreased in 2 of 5 spatial frequencies studieds. The reverse opening (anterior facing back) of one IOL at the time of implantation caused a significant loss of endothelial cells in this eye / Doutorado / Oftalmologia / Doutor em Ciências Médicas

Orientador: Maria Elisabete Rodrigues Freire Gaparetto / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-22T00:37:44Z (GMT). No. of bitstreams: 1 Nilsen_MayaraLarissa_M.pdf: 13542367 bytes, checksum: 2c541a68bc9e258aec285432b8188965 (MD5) Previous issue date: 2012 / Resumo: Dentre as ações necessárias de promoção de saúde, destaca-se a promoção da saúde ocular, pois, segundo a Organização Mundial de Saúde, aproximadamente 70% dos casos de cegueira mundial poderiam ser evitados se fossem realizadas ações de promoção da saúde por meio de técnicas simples como a aplicação de testes para avaliar a acuidade visual. Considerando tais afirmações este estudo teve como objetivos: 1) Acompanhar a inserção do enfermeiro das Estratégias de Saúde da Família na avaliação da acuidade visual de crianças matriculadas na 1a série do ensino fundamental do município de Limeira; 2) Avaliar a acuidade visual dessas crianças. Método: Realizou-se estudo analítico com crianças da 1a serie do ensino fundamental de 05 escolas do município de Limeira/SP com a participação dos enfermeiros que atuam nas Estratégias de Saúde da Família. As variáveis investigadas foram: sexo, idade, identificação da escola, avaliação da acuidade visual, uso de lentes corretivas, valores da acuidade visual e os sintomas apresentados durante a avaliação. Os instrumentos utilizados foram à tabela de Snellen e um questionário que foi aplicado às crianças por meio de entrevista. Resultados: A amostra foi composta por 143 crianças, sendo 55,9% do sexo feminino e 44,1% do sexo masculino com idade média de 5,95 anos. A média geral da acuidade visual foi de 0,857 para o olho direito; 0,846 para o olho esquerdo e 0,913 em ambos os olhos. Dessas crianças 2,1% já utilizavam correção e 17,5% apresentaram sintomas indicativos de dificuldade visual durante a realização do teste, com a prevalência do sinal de franzir de testa em 11,9% das crianças. Os resultados evidenciaram que em 7,0% das crianças houve diferença de acuidade visual entre o olho direito e o olho esquerdo. Foi verificada significância entre a acuidade visual e a presença de sintomas de dificuldade visual, com valor de p?0,05 que foi correlacionado por meio do teste de Mann-Whitney U. Foram encaminhadas 38 (26,6%) crianças ao oftalmologista. Conclusão: Considerando a interferência dos problemas visuais na aprendizagem, foi realizada a promoção da saúde ocular na escola e verificou-se que após a capacitação, o enfermeiro do programa de saúde da família pode contribuir na detecção precoce de problemas visuais, contribuindo para a diminuição de repetência e da evasão escolar / Abstract: Among the actions needed to promote health, there is the promotion of eye health because, according to the World Health Organization, approximately 70% of cases of blindness worldwide could be prevented if they were carried out actions to promote health through techniques simple as the application of tests to assess visual acuity. Considering such statements this study aimed to: 1) Monitor the insertion of nurses Strategies of Family Health in visual acuity of children enrolled in the first grade of the city of Limeira, 2) evaluate the visual acuity of these children. Method: We performed analytical study with children of primary school first series of 05 schools in the city of Limeira / SP with the participation of nurses working in Family Health Strategies. The variables were: gender, age, school ID, visual acuity, corrective lenses, values of visual acuity and symptoms during the evaluation. The instruments used were the Snellen chart and a questionnaire that was administered to children through interviews. Results: The sample consisted of 143 children, with 55.9% female and 44.1% male with an average age of 5.95 years. The average visual acuity was 0.857 for the right eye; 0.846 to 0.913 and left eye to both eyes. 2.1% of these children were using correction and 17.5% had symptoms indicative of visual difficulty during the test, with the prevalence signal frown in 11.9% of children. The results showed that 7.0% of children were no difference in visual acuity between the right eye and the left eye. Significance was found between visual acuity and symptoms of visual impairment, with p ? 0.05 which was correlated by means of the Mann-Whitney U test Were referred 38 (26.6%) children the ophthalmologist. Conclusion: Considering the interference of visual problems in learning, was held to promote eye health in school and it was found that after the training, the nurse of the family health program can help in early detection of visual problems, contributing to the decrease Repetition and dropout / Mestrado / Interdisciplinaridade e Reabilitação / Mestra em Saúde, Interdisciplinaridade e Reabilitação

D.Phil. / Visual acuity and refractive state probably are the two most basic or fundamental quantities that concern optometry, ophthalmology and vision science. Both of these variables are complicated and their mathematical and statistical use in research and other activities has been poorly understood. During particularly the last decade, modern statistical multivariate methods have become available to optometry and ophthalmology and this has assisted with the understanding of concepts such as refractive state (and its underlying nature, namely, dioptric power). It is now possible to transform measurements of refractive state from the conventional notation that is commonly used in the fields of optometry and ophthalmology to an orthodox mathematical form that can be understood by scientists and mathematicians. With this matrix form of refractive state it then is possible to use appropriate methods of linear algebra and multivariate statistics. Other theoretical approaches and analytical procedures or methods also have become accessible or have been developed recently as a consequence of this significant shift in thought as regards the fundamental nature of dioptric power. On the other hand, the scientific understanding of visual acuity (that is, the measurement of the resolving ability of the eye) perhaps has been somewhat neglected. Certainly there has been an abundance of research involving visual acuity and there also has been discussion concerning some of the difficulties that become apparent when measuring or attempting to interpret results from studies involving visual acuity. Visual acuity, unlike refractive state, can be represented by means of a single number and thus univariate, rather than multivariate, statistical methods are appropriate. And, of course, univariate statistics is less complicated than the multivariate form. But there are various difficulties with the understanding and researching of visual acuity. Some of these difficulties are relatively simple and thus can be solved more easily. For example, visual acuity measurements can be obtained from charts designed according to a logarithmic scale, or measurements from other charts can be transformed to a logarithmic scale. And thereby the ordinal nature of the basic or more common visual acuity scale is avoided and certain statistical methods become available that otherwise would not be possible. But more fundamentally visual acuity probably cannot truly be considered without the subject from which the measurement is obtained and, more particularly, the refractive state of the eye concerned. So the visual acuity and refractive state of an eye, perhaps, should be more appropriately regarded as a unitary concept that ideally should not be separated into two distinct parts. Thus to truly understand the relationship between visual acuity and refractive state we need to understand the 4-dimensional (mathematical) nature of the particular relationship involved. It follows then that the relationship between visual acuity and refractive state is a multivariate problem and that multivariate methods are best suited to its consideration. If we then begin to take into account other variables such as age or the ocular health, or say, iris aperture diameter of the eye then the complicated multivariate nature of the situation becomes even more obvious. In this dissertation an attempt is made to consider the possibilities of a modern multivariate approach to studies involving visual acuity, refractive state and other variables. The methodology used in this dissertation differs from those used in previous studies involving visual acuity and refractive state and other related variables. For example, here Jackson crossed cylinders are used extensively to produce dioptric blur or defocus in experimental subjects (positive and negative spheres also are used to a more limited extent). In previous published studies spherical or, less commonly, cylindrical lenses were used instead. Another difference between this dissertation and previous research studies is that the visual stimulus that the subjects observed, generally but not always, was a meridionally-independent or non-directional letter 0. The reasons for this choice is explained in the dissertation but in other research an enormous variety of visual stimuli have been used depending upon the interests of the researchers. But even more essentially this dissertation differs significantly from that of previous studies in terms of the manner in which the various experimental and other results (for instance, that from earlier researchers such as HB Peters) are presented. Entirely new, and largely unpublished, methods are used in many parts of this dissertation that probably represent a paradigmatic transition in understanding of visual acuity and its relation to refractive state. New terms such as decompensation and accompensation surfaces of constant visual acuity and antistigmatic ellipses are defined herein. (Briefly, one imagines starting from a state of compensation (of the refractive state of, say, an eye viewing a stimulus).

Dynamic Visual Acuity (DVA) in the visual periphery has not been extensively studied. DVA is a measure of an observer's ability to resolve critical details in a target when there is relative motion between the target and the observer. This dissertation examined static and dynamic acuity in the 25-55 deg region of retinal eccentricity under a variety of conditions. Functionally, this region of the visual field is just beyond the "blind spot," but not yet in the "far" visual periphery of 60-90 deg of eccentricity. Traditionally, DVA research has been confined to the assessment of DVA for the foveal (or "central") visual system. However, the peripheral (or "ambient") visual system provides very important information content for the visual and neuro-vestibular systems. This peripheral visual information content is also used to create a sense of ego motion (termed "vection"), and for alerting the visual system to targets entering or leaving the field of view. Past findings involving visual acuity in the peripheral retina have demonstrated that peripheral acuity performance has components related to the notion of "attention" as well. This is particularly true if the peripheral vision research results are to be applied to visually and attentionally complex and/or dynamic real-world environments. In this experiment, the 25-55 deg eccentric region of the retina was tested for DVA in 50 observers. This study used a mixed four-factor research design with Eccentricity (25, 35, 45, 50, 55 deg) as a between-subjects factor. Tracking Difficulty (monitor only, easiest, moderate, most difficult tracking levels), Landolt C Target Velocities (0.0, 4.88, 14.62, and 24.40 deg/s), and Target Direction ("F/R:" fixed or random direction of target appearance) were used as within-subjects factors. A computer presented the Landolt C ring targets under the stated conditions in a random fashion. Acuity was determined for each trial by a modified descending method-of-limits approach with the Landolt C ring target gap widths utilized as the determinant for the acuity measure. The Tracking Task was designated as the primary task, with the secondary task being to indirectly observe the orientation (up, down, right, left) of the Landolt C rings being presented under the various conditions of Target Velocity and Target Direction in the retinal periphery. The resulting Analysis of Variance (ANOVA) revealed significant differences (p < 0.05) for each of the main effects of Eccentricity, Tracking Task Difficulty, Velocity, and Target Direction (F/R). Only two of the two-way interactions were found to be significant (p < 0.05)-- those of Tracking Difficulty x Target Velocity and Target Velocity x Target Direction interactions. The results are discussed in terms of the psychophysical, attention, and "tunnel vision" like models of peripheral visual performance, along with other related human factors literature in the domain of "situation awareness" that are relevant to this general problem area. The results of a separate follow-on mini-study are discussed using a Two-way Contingency Table analysis across all of the treatment conditions when verbal intrusion was embedded in the previously described experimental conditions. This mini-study revealed a significant association (p < 0.05) with not seeing the peripheral targets as accurately when intrusion was present, versus when there was no verbal intrusion. This effect was more pronounced at the highest velocities (14.62 and 24.40 deg/s) as compared with the slower ones (0 and 4.88 deg/s) in terms of the strength of the association, as assessed by a Kappa test statistic. Taken all together, and with consideration given to the relatable scientific literature, these results indicate that the more "busy" a person is with cognitive, visual, or motor-skills tasks, the more likely an individual will show degradation in static or dynamic peripheral visual acuity tasks. Peripheral vision often serves as a "warning" or "status" sensory modality for what is occurring in the local task environment, separate from the foveal visual system. Future research is suggested given the sensitivity of the peripheral visual system to these factors, particularly with regard to how factors involving the notion of attention may affect such "peripheral visual awareness" issues. These issues in turn may play an important role from a human factors and safety perspective in a variety of person-rated vehicular domains. Specific areas that are highlighted for future research in the domain of attention and "peripheral visual awareness" include the low-altitude high-performance flying realm, the flying environment more generally, and in other dynamic multi-task vehicular environments such as that encountered while simultaneously driving and using a car cellular phone. / Ph. D.

No description available.