Neste trabalho foi desenvolvido um novo instrumento para monitoramento computadorizado da curvatura da região central anterior da córnea humana durante cirurgias refrativas. Através da projeção de um disco de Plácido na córnea, imagens dos reflexos são digitalizadas e processadas. Algoritmos baseados em técnicas de visão computacional e óptica geométrica determinam a curvatura da região central (-7 mm em diâmetro), com alta precisão e desempenho. Mapas coloridos com códigos de cor em dioptrias (proporcionais ao inverso do raio de curvatura) são gerados para auxiliar o oftalmologista durante a cirurgia. / In this work we have developed a new instrument for computerized monitoring of corneal central curvature during surgery. By projecting Placido Rings on the cornea, images of the reflections are digitized and processed. Algorithms based on computational vision and optical geometry determine the central curvature (-7 mm in diameter), with high performance and precision. Color coded maps in diopters (proportional to the inverse of the radius of curvature) are generated to aid the ophthalmologist during surgery.

by Hiu-ming Li. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 81-88). / SUMMARY --- p.1 / Chapter CHAPTER 1. --- INTRODUCTION --- p.3 / Chapter CHAPTER 2. --- LITERATURE REVIEW --- p.7 / Chapter 2.1. --- Retinal pigment epithelium --- p.7 / Chapter 2.1.1. --- Embryology / Chapter 2.1.2. --- Anatomy and histology / Chapter 2.1.3. --- Growth and aging / Chapter 2.1.4. --- Macular region / Chapter 2.2. --- The photoreceptor outer segment --- p.12 / Chapter 2.3. --- Lipofuscin --- p.13 / Chapter 2.4. --- Lipofuscin in retinal pigment epithelium and retinal photoreceptor disc shedding --- p.14 / Chapter 2.5. --- Possible mechanism for lipofuscin formation in the RPE --- p.22 / Chapter 2.6. --- Age-related lipofuscin accumulation in the RPE --- p.22 / Chapter 2.7. --- Racial difference of RPE lipofuscin concentration --- p.25 / Chapter 2.8. --- RPE lipofuscin and age-related macular degeneration --- p.26 / Chapter CHAPTER 3. --- MATERIALS AND METHODS --- p.28 / Chapter 3.1. --- Histologic Specimens --- p.28 / Chapter 3.2. --- Measuring equipment --- p.28 / Chapter 3.3. --- Software of measurements --- p.31 / Chapter 3.4. --- Light source and filters --- p.31 / Chapter 3.5. --- Control --- p.31 / Chapter 3.6. --- Measurement of autofluorescent Intensity --- p.32 / Chapter 3.7. --- Bleaching (oxidation) of melanin --- p.39 / Chapter CHAPTER 4. --- RESULTS --- p.42 / Chapter 4.1. --- Bleaching test --- p.42 / Chapter 4.2. --- RPE autofluorescence observation in different age --- p.43 / Chapter 4.3. --- RPE autofluorescence observation within individual eyes --- p.45 / Chapter 4.4. --- Topographic distribution of lipofuscin --- p.49 / Chapter 4.5. --- Lipofuscin content at the Foveola --- p.50 / Chapter 4.6. --- The relationship of age and lipofuscin content in total RPE --- p.51 / Chapter 4.7. --- The relationship of age and lipofuscin content in the macular RPE --- p.57 / Chapter 4.8. --- Relationship of age and lipofuscin content in the posterior pole of RPE --- p.59 / Chapter 4.9. --- Relationship of age and lipofuscin content in the temporal RPE --- p.61 / Chapter 4.10. --- Relationship of age and lipofuscin content in the nasal RPE --- p.63 / Chapter 4.11. --- Age related topographic changes --- p.65 / Chapter 4.12. --- The relationship of age and lipofuscin content in the RPE of male --- p.66 / Chapter 4.13. --- The relationship of age and lipofuscin content in the RPE of female --- p.68 / Chapter 4.14. --- Relationship of lipofuscin content in different sex --- p.70 / Chapter CHAPTER 5. --- DISCUSSION --- p.71 / Chapter 5.1. --- Evaluation of method --- p.71 / Chapter 5.2. --- RPE lipofuscin content in different age --- p.71 / Chapter 5.3. --- Topographic distribution of lipofuscin --- p.74 / Chapter 5.4. --- Lipofuscin and age-related macular degeneration in Chinese --- p.78 / REFERENCES --- p.81

Zhang Lin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 68-86). / Abstracts in English and Chinese. / ACKNOWLEDGEMENTS --- p.i / TABLE OF CONTENTS --- p.ii / ABBREVIATIONS --- p.v / LIST OF TABLES --- p.vi / LIST OF FIGURES --- p.vii / Chapter 1. --- ABSTRACT (ENGLISH/CHINESE) --- p.1 / Chapter 2. --- INTRODUCTION --- p.6 / Chapter 3. --- LITERATURE REVIEW --- p.9 / Chapter 3.1. --- MYOPIA IN HUMAN --- p.9 / Chapter 3.1.1. --- Different types of myopia --- p.9 / Chapter 3.1.2. --- The pathologic change of myopia --- p.10 / Chapter 3.1.3. --- The prevalence of myopia --- p.13 / Chapter 3.1.4. --- Hereditary influence in human myopia --- p.13 / Chapter 3.1.5. --- Environmental influence in human myopia --- p.15 / Chapter 3.1.6. --- Nutrition in human myopia --- p.16 / Chapter 3.1.7. --- Pharmacological agents used to prevent progression of myopia --- p.16 / Chapter 3.1.8. --- Contact lens in the prevention of progression human myopia --- p.17 / Chapter 3.2. --- ANIMAL MODELS OF EXPERIMENTAL MYOPIA --- p.19 / Chapter 3.2.1. --- Experimental myopia in monkeys --- p.19 / Chapter 3.2.2. --- Experimental myopia in three shrew --- p.21 / Chapter 3.2.3. --- Experimental myopia in marmosets and guinea pigs --- p.23 / Chapter 3.2.4. --- Experimental myopia in chicks --- p.24 / Chapter 3.2.5. --- Summary --- p.26 / Chapter 3.3. --- PHARMACOLOGICAL STUDIES --- p.27 / Chapter 4. --- OBJECTIVES --- p.32 / Chapter 5. --- materials and methods --- p.34 / Chapter 5.1. --- ANIMALS AND INDUCTION OF FORM DEPRIVATION MYOPIA --- p.34 / Chapter 5.2. --- EYE GROWTH AND MYOPIC STUDY --- p.35 / Chapter 5.2.1. --- Refractive measurements --- p.35 / Chapter 5.2.2. --- Ultrasonographic measurements of eye size in vivo --- p.35 / Chapter 5.2.3. --- Measurements with calipers on enucleated eyes --- p.36 / Chapter 5.2.4. --- Weight of eye globes --- p.36 / Chapter 5.3. --- RETINAL CHANGE --- p.36 / Chapter 5.3.1. --- Light microscopy --- p.36 / Chapter 5.3.2. --- Calretinin immuno-reactivity study of the myopic retina --- p.37 / Chapter 5.4. --- DETECTION OF APOPTOTIC CELL DEATH --- p.38 / Chapter 5.4.1. --- TUNEL --- p.38 / Chapter 5.5. --- EFFECT OF RETINAL TOXINS ON MYOPIC EYES --- p.39 / Chapter 5.5.1. --- Intravitreal injection of iodoacetic acid (IAA) --- p.39 / Chapter 5.5.2. --- Intravitreal injection of glutamic acid --- p.40 / Chapter 5.5.3. --- "Intravitreal injection of 5,7-dihydrowytryptamine (5,7-DHT)" --- p.40 / Chapter 5.6. --- EFFECT OF LIGHTING ON MYOPIC EYES --- p.41 / Chapter 6. --- RESULTS --- p.42 / Chapter 6.1. --- REFRACTIVE STATES --- p.42 / Chapter 6.2. --- EYE SIZE MEASUREMENTS --- p.42 / Chapter 6.2.1. --- Ultrasonographic measurements in vivo --- p.42 / Chapter 6.2.2. --- Caliper measurements of chick eyes ex vivo --- p.43 / Chapter 6.3. --- WEIGHT OF EYE GLOBES --- p.45 / Chapter 6.4. --- RETINAL CHANGE --- p.45 / Chapter 6.4.1. --- Morphological features --- p.45 / Chapter 6.4.2. --- Morphometry of calretinin immuno-positive cells --- p.46 / Chapter 6.5. --- EFFECT OF RETINAL TOXINS ON MYOPIC EYE --- p.46 / Chapter 6.5.1. --- Intravitreal injection of iodoacetic acid (IAA) --- p.46 / Chapter 6.5.1.1. --- Eye growth measurements --- p.47 / Chapter 6.5.1.2. --- Retinal histological features --- p.47 / Chapter 6.5.2. --- Intravitreal injection of glutamic acid --- p.48 / Chapter 6.5.2.1. --- Eye growth measurements --- p.48 / Chapter 6.5.2.2. --- Retinal histological features --- p.49 / Chapter 6.5.3. --- "Intravitreal injection of 5,7,-dihydrowytryptamine (5,7-DHT)" --- p.50 / Chapter 6.5.3.1. --- Eye growth measurements --- p.50 / Chapter 6.5.3.2. --- Retinal histological features --- p.50 / Chapter 6.6. --- EFFECT OF LIGHTING ON MYOPIC EYES --- p.51 / Chapter 6.6.1. --- Eye growth measurements --- p.51 / Chapter 6.6.2. --- Retinal histological features --- p.51 / Chapter 7. --- DISCUSSION --- p.53 / Chapter 7.1. --- REFRACTIVE STATES --- p.55 / Chapter 7.2. --- CHANGE IN EYE SIZE --- p.56 / Chapter 7.2.1. --- The rate of eye growth --- p.56 / Chapter 7.2.2. --- Ultrasonographic measurements --- p.57 / Chapter 7.2.3. --- Axial length change with caliper measurements --- p.58 / Chapter 7.3. --- MORPHOLOGY AND MORPHOMETRY OF MYOPIC RETINA --- p.58 / Chapter 7.4. --- EFFECT OF RETINAL TOXINS ON MYOPIC EYES --- p.60 / Chapter 7.4.1. --- Intravitreal injection of iodoacetic acid --- p.60 / Chapter 7.4.2. --- Intravitreal injection of glutamic acid --- p.61 / Chapter 7.4.3. --- "Intravitreal injection of 5,7-DHT" --- p.63 / Chapter 7.5. --- EFFECT OF LIGHTING ON MYOPIC EYES --- p.64 / Chapter 8. --- CONCLUSION --- p.66 / BIBLIOGRAPHY --- p.68

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS. / Vita. / Bibliography: leaves 233-238. / by Byron Kurt Lightenberg. / Sc.D.

The monkey lateral intraparietal area (LIP) is involved in visual attention and eye movements. It has traditionally been studied using extracellular recording, where often a single neuron is recorded at a time. Thus we have a wealth of correlational knowledge of what LIP neurons do, but not how or why, i.e. we do not know the circuit mechanisms and functions of the observed LIP activity. In this thesis, we have aimed to uncover the circuit mechanisms underlying LIP activity by building tightly constrained computational models. In Part 1, we found that during two versions of a delayed-saccade task, beneath similar population average firing patterns across time lie radically different network dynamics. When neurons are not influenced by stimuli outside their receptive fields (RFs), dynamics of the high-dimensional LIP network lie predominantly in one multi-neuronal dimension, as predicted by an earlier model. However, when activity is suppressed by stimuli outside the RF, LIP dynamics markedly deviate from a single dimension. The conflicting results can be reconciled if two LIP local networks, each dominated by a single multi-neuronal activity pattern, are suppressively coupled to each other. These results demonstrate the low dimensionality of LIP local dynamics and suggest active involvement of LIP recurrent circuitry in surround suppression and, more generally, in processing attentional and movement priority and in related cognitive functions. In Part 2, we examine the mechanisms of learning in LIP. When monkeys learn to group visual stimuli into arbitrary categories, LIP neurons become category-selective. Surprisingly, the representations of learned categories are overwhelmingly biased: while different categories are behaviorally equivalent, nearly all LIP neurons in a given animal prefer the same category. We propose that Hebbian plasticity, at the synapses to LIP from prefrontal cortex and from lower sensory areas, could lead to the development of biased representations. In our model, LIP category selectivity arises due to competition between inputs encoding different categories, and bias develops due to excitatory lateral interactions among LIP neurons. This model reproduces the different levels of category selectivity and bias observed in multiple experiments. Our results suggest that the connectivity of LIP allows it to learn the behavioral importance of stimuli in order to guide attention.

Multiple elements of the retail environment can have an impact on a consumer's behaviour and purchase decisions. Much of the influence that the environment has on behaviour often goes unnoticed, as it affects internal processes that happen below the level of conscious awareness. This research aims to explore and quantify the effect a retail environment has on consumers' affective (emotional) and cognitive responses towards products. Priming is the influence of external stimuli on one's behaviour or response towards target stimuli. This research designed an experiment to prime participants with a particular coloured stimulus (pink, blue, or red) in order to measure the influence of this prime on the participants' purchase decisions. The participants entered a real-world simulated retail shop, and within a guided format they shopped through the available dresses, eventually picking out their three ranked favourites. The participants' physiological responses were measured using an eye-tracker and a portable Electroencephalogram (EEG) recording unit. The eye-tracking data were analysed using the Gaze Cascade Theory, testing for an increase in gaze bias towards preferred and primed products. The EEG data provided information about the participants' brain activity, and were analysed in accordance with Davidson's model of emotion, indicating an approach or withdrawal tendency towards different products. The results showed that with both eye-tracking and EEG it is possible to measure a difference between the participants' cognitive and affective responses towards the products that they preferred and chose as their favourites, compared with the products they did not choose. The EEG data provided evidence of a difference in neural responses between the prime matching coloured products and the non-prime matching products. However, the eye-tracking responses did not demonstrate a significant difference in eye-movements between the primed and not primed products. Technical innovation was required to allow the recording of EEG data in the semi-controlled shop environment, to allow data free of motion artefacts to be analysed. These results demonstrate the ability to measure consumers' physiological, neural, and subconscious responses in a real-world retail environment, whilst allowing the participants to move freely and unhindered. A novel methodology for analysing motion artefact free EEG data is presented. The results demonstrate a significant difference in emotional responses, as detected by EEG, in preference towards the prime coloured products, suggesting that priming has an influence in decision making in fashion retail environments.

The primary aim of this thesis was to identify the mechanism under-pinning the word-predictability effect, while a secondary aim was to investigate whether words are processed in serial or parallel. In five experiments, adults’ eye-movements were monitored as they read sentences for comprehension on a computer screen. In Experiments 1 and 2, a critical target-word that was either of high- or low-frequency and either predictable or unpredictable was embedded in experimental sentences. The nature of the preview of the target word was manipulated such that it was either identical to the target or was misspelled (the misspelling was more severe in Experiment 2). Predictability effects were apparent in the identical preview condition in both experiments, whilst they were only apparent in the misspelled condition of Experiment 1. This outcome is compatible with early Guessing Game type models of reading which propose that readers predictions about up-coming words using contextual parafoveal information. When taken together, the results of Experiments 1 and 2 also suggested that frequency and predictability exert additive effects on fixation durations.In Experiment 3, four levels of word-predictability were employed. The function relating word-predictability and word-processing time was strictly monotonic: word-processing time decreased as predictability increased. This outcome was consistent with a word-prediction account of predictability in which there is no penalty for incorrect guessing. Experiment 3 also showed that processing time on the pre-target word increased as the predictability of the up-coming increased. This outcome replicated an effect obtained by Kliegl, Nuthmann and Engbert (2006) who claim that it arises as a result of memory retrieval processes cued by prior sentence context Experiment 4 replicated the manipulation in Experiment 3 but included additional condition in which the preview of the target word was masked while in parafoveal vision, using a pixel scrambling technique. The target-predictability effect was again a graded one, and did not depend upon the availability of initial information, providing evidence against the word-prediction theory. Additionally, there was no pre-target predictability effect in the unmasked condition. There was a pre-target effect in an direction in the masked condition, although this appeared to be a consequence of the mask. Experiment 5 replicated Experiment 4, but replaced the masked condition with a non-predictable but semantically related word, and the results showed no pre-target effects at all. It was concluded that inverted pre-predictability effects are more likely to be related to higher-level sentential processing.

The research reported in the present explored the interaction between perception and action, focusing on how this might occur under memory conditions. This was done in line with the proposals of grounded cognition and situated action, in which action and perception are tightly linked, and able to influence one another in order to aid the performance of a task. Following this idea of a bi-directional loop between the two processes, studies were conducted which focused on each side of this relationship, in conditions where memory would be necessary. The first experiments investigated how the perception of objects and the memory of those perceived objects could influence the production of actions. Later studies examined how the preparation and performance of actions could affect the perception of a scene, and subsequent recall of the objects presented. Throughout these studies, object properties (e.g., shape, colour, position) were used as a means to either manipulate or measure the effect of the tasks. The findings of the studies suggested that weighting an off-line memory representation by means of the task setting was possible, but that this was not an automatic occurrence. Based on the results obtained, it seemed that there were conditions which would affect whether memories could be tailored to the current demands of the tasks, and that these conditions were linked to the realism of the situation. Factors such as the task complexity, the potential for object interaction and the immersive environment were all suggested as possible contributors to the construction and use of weighted representations. Overall, the studies conducted suggest that memory can play a role in guiding action, as on-line perception does, so long as the situation makes it clear that this is necessary. If such weightings are useful, then the memory will be constructed accordingly. However, if the situation is such that there is no clear task, then the memory representations will remain unaffected and unprepared for one specific action, or not be used to aid action. Memory can be seen as serving action, but our memory systems are flexible, allowing us to cope with the demands and restrictions of particular situations.

We live in a rich visual world that we experience as a seamless and detailed stream of continuous information. However, we can only attend to and remember a small portion of our visual environment. The visual system is tasked with stitching together snapshots of the world through near constant eye movements, with around three saccades per second. The situation is further complicated with the visual system being contralaterally organized. Each eye movement can bring items in our environment into a different visual hemifield. Despite the many challenges and limitations of attention and the visual system, how does the brain stitch together our experience of our visual environment? One potential mechanism that could contribute to our conscious perception of a continuous visual experience could be visual working memory (VWM) working to maintain representations of items across saccades. Electrophysiological activity using event-related potentials has revealed the contralateral delay activity (CDA), which is a sustained negativity contralateral to the side of the visual field where subjects are attending. However, how does this work if we are constantly moving our eyes? How do we form a stable representation of items across eye movements? Does the representation transfer over to the other side of the brain, constantly shuffling the items between the hemispheres? Or does it stay in the hemisphere contralateral to the visual field where the items were located when we originally created the representation? The consequences of eye movements need to be examined at multiple levels and time points throughout the process. The goal of my doctoral dissertation is to investigate VWM representations throughout the dynamic peri-saccadic window. In Experiment 1, I will first compare VWM representations across shifts of attention and eye position. With the focus on the effect of maintaining attention on items across eye movements, Experiment 2 will also explore eye movements both towards and away from attended visual hemifields. Finally, Experiment 3 is designed to substantiate our use of the CDA as a tool for examining VWM representations across eye movements by confirming that the CDA is indeed established in retinotopic coordinates.

Heritable retinal degenerations dramatically affect individuals across the lifespan. Heritable degenerations with onset in childhood or young adulthood, such as the ABCA4- associated maculopathies, generally obey Mendelian segregation and are attributable to mutations within a single gene. Retinal degenerations with onset in late adulthood, such as age-related macular degeneration, are usually influenced by a complex constellation of genetic and environmental factors. This thesis applies several complementary, high-throughput genotyping platforms to identify relationships between specific heritable retinal phenotypes and genetic variation. This findings of this thesis will aid in the development of guidelines for inclusion in retinal gene therapy trials and help physicians refine their prognoses based on genetic information.