859 resultados para EYE


Relevância:

20.00% 20.00%

Publicador:

Resumo:

An optical coherence tomography (OCT) system to produce both longitudinal and transversal images of the in vivo human eye is presented. For the first time, OCT transversal images collected from the living eye at 50-µm depth steps show details unobtainable with the state-of-the-art scanning laser ophthalmoscope. Images of up to 3×3?mm are produced from the retina in less than a second. For images larger than 1.6×1.6?mm, a path modulation is introduced by the galvanometric scanning mirror and is used as an effective phase modulation method.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Visual mental imagery is a process that draws on different cognitive abilities and is affected by the contents of mental images. Several studies have demonstrated that different brain areas subtend the mental imagery of navigational and non-navigational contents. Here, we set out to determine whether there are distinct representations for navigational and geographical images. Specifically, we used a Spatial Compatibility Task (SCT) to assess the mental representation of a familiar navigational space (the campus), a familiar geographical space (the map of Italy) and familiar objects (the clock). Twenty-one participants judged whether the vertical or the horizontal arrangement of items was correct. We found that distinct representational strategies were preferred to solve different categories on the SCT, namely, the horizontal perspective for the campus and the vertical perspective for the clock and the map of Italy. Furthermore, we found significant effects due to individual differences in the vividness of mental images and in preferences for verbal versus visual strategies, which selectively affect the contents of mental images. Our results suggest that imagining a familiar navigational space is somewhat different from imagining a familiar geographical space. © 2014 Elsevier Ireland Ltd.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Along with other diseases that can affect binocular vision, reducing the visual quality of a subject, Congenital Nystagmus (CN) is of peculiar interest. CN is an ocular-motor disorder characterized by involuntary, conjugated ocular oscillations and, while identified more than forty years ago, its pathogenesis is still under investigation. This kind of nystagmus is termed congenital (or infantile) since it could be present at birth or it can arise in the first months of life. The majority of CN patients show a considerable decrease of their visual acuity: image fixation on the retina is disturbed by nystagmus continuous oscillations, mainly horizontal. However, the image of a given target can still be stable during short periods in which eye velocity slows down while the target image is placed onto the fovea (called foveation intervals). To quantify the extent of nystagmus, eye movement recordings are routinely employed, allowing physicians to extract and analyze nystagmus main features such as waveform shape, amplitude and frequency. Use of eye movement recording, opportunely processed, allows computing "estimated visual acuity" predictors, which are analytical functions that estimate expected visual acuity using signal features such as foveation time and foveation position variability. Hence, it is fundamental to develop robust and accurate methods to measure both those parameters in order to obtain reliable values from the predictors. In this chapter the current methods to record eye movements in subjects with congenital nystagmus will be discussed and the present techniques to accurately compute foveation time and eye position will be presented. This study aims to disclose new methodologies in congenital nystagmus eye movements analysis, in order to identify nystagmus cycles and to evaluate foveation time, reducing the influence of repositioning saccades and data noise on the critical parameters of the estimation functions. Use of those functions extends the information acquired with typical visual acuity measurement (e.g., Landolt C test) and could be a support for treatment planning or therapy monitoring. © 2010 by Nova Science Publishers, Inc. All rights reserved.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Congenital nystagmus is an ocular-motor disorder that develops in the first few months of life; its pathogenesis is still unknown. Patients affected by congenital nystagmus show continuous, involuntary, rhythmical oscillations of the eyes. Monitoring eye movements, nystagmus main features such as shape, amplitude and frequency, can be extracted and analysed. Previous studies highlighted, in some cases, a much slower and smaller oscillation, which appears added up to the ordinary nystagmus waveform. This sort of baseline oscillation, or slow nystagmus, hinder precise cycle-to-cycle image placement onto the fovea. Such variability of the position may reduce patient visual acuity. This study aims to analyse more extensively eye movements recording including the baseline oscillation and investigate possible relationships between these slow oscillations and nystagmus. Almost 100 eye movement recordings (either infrared-oculographic or electrooculographic), relative to different gaze positions, belonging to 32 congenital nystagmus patients were analysed. The baseline oscillation was assumed sinusoidal; its amplitude and frequency were computed and compared with those of the nystagmus by means of a linear regression analysis. The results showed that baseline oscillations were characterised by an average frequency of 0.36 Hz (SD 0.11 Hz) and an average amplitude of 2.1° (SD 1.6°). It also resulted in a considerable correlation (R2 scored 0.78) between nystagmus amplitude and baseline oscillation amplitude; the latter, on average, resulted to be about one-half of the correspondent nystagmus amplitude. © 2009 Elsevier Ltd. All rights reserved.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Here we report the assessment and treatment of a 6-year-old boy (L.G.) who was referred to us for congenital prosopagnosia (CP). We investigated his performance using a test battery and eye movement recordings pre- and post-training. L.G. showed deficits in recognising relatives and learning new faces, and misrecognition of unfamiliar people. Eye movement recordings showed that L.G. focused on the lower part of stimuli in naming tasks based on familiar or unfamiliar incomplete or complete faces. The training focused on improving his ability to explore internal features of faces, to discriminate specific facial features of familiar and unfamiliar faces, and to provide his family with strategies to use in the future. At the end of the training programme L.G. no longer failed to recognise close and distant relatives and classmates and did not falsely recognise unknown people.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The approach of all ophthalmologists, diabetologists and general practitioners seeing patients with diabetic retinopathy should be that good control of blood glucose, blood pressure and plasma lipids are all essential components of modern medical management. The more recent data on the use of fenofibrate in the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) and The Action to Control Cardiovascular Risk in Diabetes (ACCORD) Eye studies is reviewed. In FIELD, fenofibrate (200 mg/day) reduced the requirements for laser therapy and prevented disease progression in patients with pre-existing diabetic retinopathy. In ACCORD Eye, fenofibrate (160 mg daily) with simvastatin resulted in a 40% reduction in the odds of retinopathy progressing over 4 years, compared with simvastatin alone. This occurred with an increase in HDL-cholesterol and a decrease in the serum triglyceride level in the fenofibrate group, as compared with the placebo group, and was independent of glycaemic control. We believe fenofibrate is effective in preventing progression of established diabetic retinopathy in type 2 diabetes and should be considered for patients with pre-proliferative diabetic retinopathy and/or diabetic maculopathy, particularly in those with macular oedema requiring laser. © 2011 Macmillan Publishers Limited All rights reserved.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Aim: To assess whether the current starting age of 12 is suitable for diabetic retinopathy (DR) screening and whether diabetes duration should be taken into account when deciding at what age to start screening patients. Materials and methods: A retrospective analysis of 143 patients aged 12 years or younger who attended diabetic eye screening for the first time in the Birmingham, Solihull and Black Country Diabetic Eye Screening Programme was performed. Results: The mean age of the patients was 10.7 (7-12) years with 73 out of 143 aged below 12 years and 70 were 12 years of age. 98% had type 1 diabetes and mean diabetes duration was 5 (1 month-11 years) years. For those younger than 12 years, 7/73 (9.6%) had background DR (BDR), of these mean diabetes duration was 7 years (6-8). The youngest patient to present with DR was aged 8 years. In those aged 12 years, 5/70 (7.1%) had BDR; of these mean diabetes duration was 8 years (6-11). No patient developed DR before 6 years duration in either group. Conclusions: The results show that no patient younger than the age of 12 had sight-threatening DR (STDR), but BDR was identified. Based on the current mission statement of the Diabetic Eye Screening Programme to identify STDR, 12 years of age is confirmed as the right age to start screening, but if it is important to diabetic management to identify first development of DR, then screening should begin after 6 years of diabetes diagnosis.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This article provides an overview of the various eye-related causes of photophobia and the likely mechanisms responsible. Photophobia is an experience of discomfort affecting the eyes due to exposure to light. It has a variety of causes including the result of eye or brain disease, or it can be a side effect of various drugs or laser surgery. Photophobia can also be a symptom of a more serious disorder such as meningitis and therefore, requires appropriate investigation, diagnosis, and treatment. Trauma or disease affecting several structures of the eye are a common cause of photophobia and can be associated with: (1) the ocular adnexia, such as blepharitis and blepharospasm, (2) the cornea, including abrasion, ulcerative keratitis, and corneal dystrophy, (3) problems in eye development, such as aniridia, buphthalmos, coloboma, and aphakia, (4) various eye inflammations, including uveitis, and (5) retinal disorders, such as achromatopsia, retinal detachment, and retinal dystrophy. There may be two main explanations for eye-related photophobia: (1) direct stimulation of the trigeminal nerve due to damage, disease, or excessive light entering the eye and (2) overstimulation of the retina including a specific population of light-sensitive ganglion cells.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This study aimed to: i) determine if the attention bias towards angry faces reported in eating disorders generalises to a non-clinical sample varying in eating disorder-related symptoms; ii) examine if the bias occurs during initial orientation or later strategic processing; and iii) confirm previous findings of impaired facial emotion recognition in non-clinical disordered eating. Fifty-two females viewed a series of face-pairs (happy or angry paired with neutral) whilst their attentional deployment was continuously monitored using an eye-tracker. They subsequently identified the emotion portrayed in a separate series of faces. The highest (n=18) and lowest scorers (n=17) on the Eating Disorders Inventory (EDI) were compared on the attention and facial emotion recognition tasks. Those with relatively high scores exhibited impaired facial emotion recognition, confirming previous findings in similar non-clinical samples. They also displayed biased attention away from emotional faces during later strategic processing, which is consistent with previously observed impairments in clinical samples. These differences were related to drive-for-thinness. Although we found no evidence of a bias towards angry faces, it is plausible that the observed impairments in emotion recognition and avoidance of emotional faces could disrupt social functioning and act as a risk factor for the development of eating disorders.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The purpose of this inquiry was to investigate the impact of a large, urban school district's experience in implementing a mandated school improvement plan and to examine how that plan was perceived, interpreted, and executed by those charged with the task. The research addressed the following questions: First, by whom was the district implementation plan designed, and what factors were considered in its construction? Second, what impact did the district implementation plan have on those charged with its implementation? Third, what impact did the district plan have on the teaching and learning practices of a particular school? Fourth, what aspects of the implemention plan were perceived as most and least helpful by school personnel in achieving stated goals? Last, what were the intended and unintended consequences of an externally mandated and directed plan for improving student achievement? The implementation process was measured against Fullan's model as expounded upon in The Meaning of Educational Change (1982) and The New Meaning of Educational Change (1990). The Banya implementation model (1993), because it added a dimension not adequately addressed by Fullan, was also considered.^ A case study was used as the methodological framework of this qualitative study. Sources of data used in this inquiry included document analysis, participant observations in situ, follow-up interviews, the "long" interview, and triangulation. The study was conducted over a twelve-month period. Findings were obtained from the content analysis of interview transcripts of multiple participants. Results were described and interpreted using the Fullan and Banya models as the descriptive framework. A cross-case comparison of the multiple perspectives of the same phenomena by various participants was constructed.^ The study concluded that the school district's implementation plan to improve student achievement was closely aligned to Fullan's model, although not intentionally. The research also showed that where there was common understanding at all levels of the organization as to the expectations for teachers, level of support to be provided, and availability of resources, successful implementation occured. The areas where successful implementation did not occur were those where the complexity of the changes were underestimated and processes for dealing with unintended consequences were not considered or adequately addressed. The unique perspectives of the various participants, from the superintendent to the classroom teacher, are described. Finally, recommendations for enhancement of implementation are offered and possible topics for further research studies are postulated. ^

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This research pursued the conceptualization and real-time verification of a system that allows a computer user to control the cursor of a computer interface without using his/her hands. The target user groups for this system are individuals who are unable to use their hands due to spinal dysfunction or other afflictions, and individuals who must use their hands for higher priority tasks while still requiring interaction with a computer. ^ The system receives two forms of input from the user: Electromyogram (EMG) signals from muscles in the face and point-of-gaze coordinates produced by an Eye Gaze Tracking (EGT) system. In order to produce reliable cursor control from the two forms of user input, the development of this EMG/EGT system addressed three key requirements: an algorithm was created to accurately translate EMG signals due to facial movements into cursor actions, a separate algorithm was created that recognized an eye gaze fixation and provided an estimate of the associated eye gaze position, and an information fusion protocol was devised to efficiently integrate the outputs of these algorithms. ^ Experiments were conducted to compare the performance of EMG/EGT cursor control to EGT-only control and mouse control. These experiments took the form of two different types of point-and-click trials. The data produced by these experiments were evaluated using statistical analysis, Fitts' Law analysis and target re-entry (TRE) analysis. ^ The experimental results revealed that though EMG/EGT control was slower than EGT-only and mouse control, it provided effective hands-free control of the cursor without a spatial accuracy limitation, and it also facilitated a reliable click operation. This combination of qualities is not possessed by either EGT-only or mouse control, making EMG/EGT cursor control a unique and practical alternative for a user's cursor control needs. ^

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Effective interaction with personal computers is a basic requirement for many of the functions that are performed in our daily lives. With the rapid emergence of the Internet and the World Wide Web, computers have become one of the premier means of communication in our society. Unfortunately, these advances have not become equally accessible to physically handicapped individuals. In reality, a significant number of individuals with severe motor disabilities, due to a variety of causes such as Spinal Cord Injury (SCI), Amyothrophic Lateral Sclerosis (ALS), etc., may not be able to utilize the computer mouse as a vital input device for computer interaction. The purpose of this research was to further develop and improve an existing alternative input device for computer cursor control to be used by individuals with severe motor disabilities. This thesis describes the development and the underlying principle for a practical hands-off human-computer interface based on Electromyogram (EMG) signals and Eye Gaze Tracking (EGT) technology compatible with the Microsoft Windows operating system (OS). Results of the software developed in this thesis show a significant improvement in the performance and usability of the EMG/EGT cursor control HCI.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

LOVE COMES IN AT THE EYE relates the story of Marshall Craig, a Midwesterner transplanted to South Florida who turns 35 in the course of the book. Marshall is an assistant curator for a Miami art museum, a man who has been obsessed with--as he calls it--a greed for seeing from a young age. His fascination with the surface of appearance of things is exacerbated by his precocious studies in art and its histories. Marshall views himself as marked by his red hair and freckled skin, as someone whose chances of attracting a partner into a meaningful relationship have been diminished by his looks. He is colored by his image of himself as unattractive and most importantly, convinced that his romantic life would be more successful, more vibrant, if he'd been graced with the face and figure of, say, a Velazquez. When Marshall meets a Cuban-born man from Atlanta, he is transfixed by the conviction that this is the man the universe has selected for him. The thrust of the story goes beyond boy-meets/loses/gets-boy to an exploration of said boy coming to terms with his definition of self. In a pivotal span of six months, the book explores Marshall's obsessions with seeing and how they define his vision of reality, the emphasis placed on beauty in gay culture, the tentative beginnings of a relationship as it takes root and grows, and finally, the inexplicable, magical forces that direct our romantic destinies.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Traditional Optics has provided ways to compensate some common visual limitations (up to second order visual impairments) through spectacles or contact lenses. Recent developments in wavefront science make it possible to obtain an accurate model of the Point Spread Function (PSF) of the human eye. Through what is known as the "Wavefront Aberration Function" of the human eye, exact knowledge of the optical aberration of the human eye is possible, allowing a mathematical model of the PSF to be obtained. This model could be used to pre-compensate (inverse-filter) the images displayed on computer screens in order to counter the distortion in the user's eye. This project takes advantage of the fact that the wavefront aberration function, commonly expressed as a Zernike polynomial, can be generated from the ophthalmic prescription used to fit spectacles to a person. This allows the pre-compensation, or onscreen deblurring, to be done for various visual impairments, up to second order (commonly known as myopia, hyperopia, or astigmatism). The technique proposed towards that goal and results obtained using a lens, for which the PSF is known, that is introduced into the visual path of subjects without visual impairment will be presented. In addition to substituting the effect of spectacles or contact lenses in correcting the loworder visual limitations of the viewer, the significance of this approach is that it has the potential to address higher-order abnormalities in the eye, currently not correctable by simple means.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

La tesi tratta l'analisi della sicurezza delle piste ciclabili di Bologna, mediante tecnologie innovative quali Mobile Eye e Video V-Box. Si trattano due percorsi: "Sabotino" e "Sant'Orsola", comprendenti ciascuno due itinerari alternativi, uno ciclabile e uno no. In prima fase, si sono somministrati dei questionari di gradimento ad un campione composto da 50 utenti per percorso. I questionari sono composti da una parte generale e da una specifica dell'itinerario. Dall'analisi dei risultati delle interviste, eseguita esclusivamente per il percorso "Sabotino", è stato possibile evidenziare le criticità segnalate dai ciclisti. Sono state poi condotte, esclusivamente nel tratto Nord-Ovest della tangenziale delle biciclette, indagini sperimentali con Mobile Eye, con lo scopo di conoscere quali elementi stradali sono maggiormente guardati e considerati dall'utente e con Video V-Box, in grado di fornire posizione, velocità puntuale e accelerazione. A tali sperimentazioni hanno partecipato 17 utenti, ignari dello scopo del test. Ottenuti i dati, sono stati analizzati i risultati provenienti da V-Box quindi analizzate le velocità in prossimità delle intersezioni significative. Dal confronto dei risultati provenienti dai questionari e dai test sperimentali è stato possibili giundere a delle conclusioni.