To see the other types of publications on this topic, follow the link: Low vision.
Dissertations / Theses on the topic 'Low vision'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Low vision.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Rahimi, Ali 1976. "Bug vision : experiments in low resolution vision." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/62362.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2001.<br>Includes bibliographical references (p. 71-73).<br>Tracking multiple people using cameras is similar to the well-studied problem of tracking multiple radar or sonar echoes. This thesis shows that current camera-based tracking algorithms convert each image in a video sequence to a list of targets through a segmentation step, and pass this target set to a traditional multiple-point-target tracking algorithm. Various tracking vision-based strategies as well as point tracking strategies are discussed. Bayesian solutions to the point-tracking problem are well understood, because the generative models need describe the dynamics of simple point objects. In addition, the radar tracking problem assumes that measurements are noise corrupted positions, which makes it easy to cast the tracking problem in a Bayesian framework. Unlike radar, cameras report observations as images. Though point object dynamics can still be used to describe the hidden state of targets, the observation model is an image formation process. As such, the typical solution to tracking in the camera-based tracking community is to reduce each image to a point set, where each point corresponds to a potential target. However, this step introduces uncertainty that is usually not modeled. This thesis proposes a Bayesian person-tracking algorithm which models the entire process of tracking, from the dynamics of the targets to the formation of easy to compute image transforms. An approximate Bayesian tracking algorithm based on Variational Bayes is developed. All the benefits of a Bayesian framework including modeling of the certainty of the recovered results and model selection are taken advantage of. The resulting person tracking algorithm can operate on extremely poor quality imagery. In addition, the tracker can compute the number of targets in the scene automatically as a side effect of its Bayesian formulation.<br>by Ali Rahimi.<br>S.M.
2
Gustafsson, Jörgen. "Optics for low vision enabling /." Lund: Certec, Dept. of Design Sciences, Univ, 2004. http://www.certec.lth.se/dok/optikforsynsvaga/.
Full text
3
Roelofs, Antonius Arnoldus Jozef. "Image enhancement for low vision /." Online version, 1997. http://bibpurl.oclc.org/web/25504.
Full text
4
Bäckman, Örjan. "Re-establishing reading skills of elderly low vision patients : studies on Swedish low vision clinic clients /." Stockholm, 2000. http://diss.kib.ki.se/2000/91-628-4577-2/.
Full text
5
Chiang, Peggy Pei-Chia. "The global mapping of low vision services." Connect to thesis, 2009. http://repository.unimelb.edu.au/10187/7119.
Full textAbstract:
Low vision impacts on Quality of Life (QoL). Thus, low vision services are essential to enhance the QoL of people with functional low vision. However, of the estimated 70 out of the 124 million people with low vision who require services, approximately 5-10% has access to services. The demands for low vision services will continue to grow due to the emerging global trends in ageing populations and changes in the epidemiology of vision impairment. While critical data and information are available for other forms of vision impairment, there is a paucity of information on the distribution, needs, and priorities for improving low vision service delivery at the national, regional, and global levels.<br>This thesis addressed the problem by first developing and distributing a survey to Vision 2020 contacts, government, and non government organisations in 195 countries during 2006-2008 to assess the current situation of low vision services globally. The survey was first pilot tested leading to improvements in the length, layout, and content of its form. Specifically, the survey topics included: epidemiology, policies, human resources, service provision, barriers, equipment, and monitoring and evaluation.<br>The Classification Analysis and Regression Tree (CART), logistic regression methodology and grounded theory analysis were used to present the findings and identify the critical success factors of low vision service coverage. The qualitative component consisted of case studies in three countries (India, Ghana, and Cameroon) during November 2007 and 2008. A total of 101 interviews were carried out. The case studies provided an overview and historical perspective of services, effectiveness, cost, efficiency, acceptability, access, equity, sustainability, and ideal situations as recommended by interviewees. Qualitative findings from the case studies were produced with the assistance of the NVivo software.<br>The primary results are that the majority (80%) of countries have poor (≤10%) coverage. Key issues pertinent to the current situation of service coverage are: human resources (number and combination of disciplines), funding (sustainability and arrangements), type of services provided (comprehensive and multidisciplinary) and its locations (NGOs or government facilities), and the sociodemographic and economic barriers (costs, awareness, and rural areas) to accessing services.<br>The critical success factors found in this research are represented by the ‘FRAME’: Funding (sustainable source, public and private mix), Rehabilitation workers (e.g., adequate numbers of multidisciplinary personnel), Access to low vision devices, Multidisciplinary services; and External contextual influences in which low vision services operate in. The case studies identified seven major themes that further build on the FRAME: sustainability, governance, advocacy, human resources, access, awareness, and service delivery.<br>The conclusion of the thesis is that a global picture of the current situation of low vision services was acquired and it is now known which countries have poor (≤10%) and better (>10%) coverage. It also found the critical success factors that will assist the WHO Low Vision Working Group and Vision 2020 to improve the current models of service delivery, future planning, training curriculum development, and priorities setting. Specifically, these need to be achieved through three areas of action: human resources development, sustainability, and advocacy.
6
Wright, Anne R. (Anne Renée). "A low-cost color vision tracking system." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10896.
Full text
7
Wallis, S. A. "Low level feature detection in human vision." Thesis, Aston University, 2009. http://publications.aston.ac.uk/15404/.
Full textAbstract:
Influential models of edge detection have generally supposed that an edge is detected at peaks in the 1st derivative of the luminance profile, or at zero-crossings in the 2nd derivative. However, when presented with blurred triangle-wave images, observers consistently marked edges not at these locations, but at peaks in the 3rd derivative. This new phenomenon, termed ‘Mach edges’ persisted when a luminance ramp was added to the blurred triangle-wave. Modelling of these Mach edge detection data required the addition of a physiologically plausible filter, prior to the 3rd derivative computation. A viable alternative model was examined, on the basis of data obtained with short-duration, high spatial-frequency stimuli. Detection and feature-making methods were used to examine the perception of Mach bands in an image set that spanned a range of Mach band detectabilities. A scale-space model that computed edge and bar features in parallel provided a better fit to the data than 4 competing models that combined information across scale in a different manner, or computed edge or bar features at a single scale. The perception of luminance bars was examined in 2 experiments. Data for one image-set suggested a simple rule for perception of a small Gaussian bar on a larger inverted Gaussian bar background. In previous research, discriminability (d’) has typically been reported to be a power function of contrast, where the exponent (p) is 2 to 3. However, using bar, grating, and Gaussian edge stimuli, with several methodologies, values of p were obtained that ranged from 1 to 1.7 across 6 experiments. This novel finding was explained by appealing to low stimulus uncertainty, or a near-linear transducer.
8
Lovie-Kitchin, Jan E. "Reading performance of adults with low vision." Thesis, Queensland University of Technology, 1996. https://eprints.qut.edu.au/36724/1/36724_Digitised%20Thesis.pdf.
Full textAbstract:
Many factors, related to the reading task, the low vision device and the patient, affect the reading performance and eventual reading rehabilitation of a patient with low vision. Reading performance can be defined in terms of near visual acuity and reading rate - both need to be adequate for reading to be functionally useful. Near visual acuity can be simply and accurately measured with standardised test charts, but the patient's potential reading rate cannot be so easily determined. In this study, reading performance of adults with low vision was examined, firstly with respect to current clinical practice by a survey of low vision clinic records and interviews with patients, and secondly, in an experimental investigation. Data on the ophthalmic characteristics of an adult low vision population were collected retrospectively from the records of a low vision clinic, with emphasis on the powers and types of near low vision devices prescribed and the patients' performances, frequency of use and satisfaction with these devices. Subjects with age related macular degeneration (ARMD) who had previously attended the low vision clinic were interviewed, to investigate their use of near optical low vision devices. In the experimental investigation, the visual functions of subjects with normal and low vision were assessed and reading rate for scrolled printed text was measured at different character sizes and with different window sizes (number of characters in the reading field).
The results confirmed that many patient variables significantly affect reading performance. However, the experimental study showed for the first time, that a high proportion of the variance in maximum reading rate for a group of subjects with normal and low vision can be predicted from standard clinically-applicable measures of visual performance. This has not previously been possible because of the use of limited sets of clinical measures. Stepwise multiple regression analysis indicated that for low vision subjects, near word visual acuity, age and right visual field size (degrees) were the strongest predictors of maximum reading rate, accounting for 80% of the variance. This study used a one-line, forced scrolled method to measure maximum oral reading rates, so further research is needed to confirm these findings for everyday reading. The experimental results found that for most patients to read at maximum or near maximum reading rate, character size needs to be 2112 times threshold print size (0.4 log acuity reserve). However, for the first time, it was clearly identified that there is an interaction between required acuity reserve and window size. Maximum reading rate can be achieved with low acuity reserve and large window sizes or high acuity reserve and small window sizes, but the latter is easier to obtain with stand or hand-held magnifiers. Thus, higher magnifications should be prescribed than those calculated from simple geometric principles. This study showed that reading performance of adults will be equivalent when magnification is supplied by either large print or optical magnifiers, provided optimum acuity reserve is provided.
While the survey of patient records and the interviews of ARMD subjects indicated that patients continue to use near low vision devices, satisfaction rates decrease over time. This may be due to progressive vision loss together with poor reading illuminances, but the factors determining satisfaction with near low vision devices were unable to be identified by this study. Low vision patients are more likely to be assisted with reading by the prescription of a near low vision device if they are referred to low vision services earlier in the course of their ocular disease, when visual acuity is relatively good. Individual program plans should be used by vision rehabilitation services to assist patients to set specific, realistic goals. The interviews with the ARMD subjects indicated the need for more follow-up care for some patients - those whose vision loss progresses and/or whose functional needs change. This, together with earlier referral of patients, has repercussions for the cost-effectiveness of low vision service delivery.
Recommendations are given on the methods of measuring visual acuity, letter contrast sensitivity and central visual fields and the use of the results for reading rehabilitation. Based on the assessment of these visual functions, predictions about the usefulness of a low vision patient's potential reading rate after prescription of, and training with, a near low vision device can be made. Further research is planned to improve reading and visual field assessment methods and to establish vision requirements for everyday reading of stationary text, which will improve the selection of appropriate reading rehabilitation programs for adults with low vision.
9
Merron, Jason S. A. "Extracting low-level image cues." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390483.
Full text
10
Johansson, Björn. "Low Level Operations and Learning in Computer Vision." Doctoral thesis, Linköpings universitet, Bildbehandling, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-24005.
Full textAbstract:
This thesis presents some concepts and methods for low level computer vision and learning, with object recognition as the primary application. An efficient method for detection of local rotational symmetries in images is presented. Rotational symmetries include circle patterns, star patterns, and certain high curvature patterns. The method for detection of these patterns is based on local moments computed on a local orientation description in double angle representation, which makes the detection invariant to the sign of the local direction vectors. Some methods are also suggested to increase the selectivity of the detection method. The symmetries can serve as feature descriptors and interest points for use in hierarchical matching structures for object recognition and related problems. A view-based method for 3D object recognition and estimation of object pose from a single image is also presented. The method is based on simple feature vector matching and clustering. Local orientation regions computed at interest points are used as features for matching. The regions are computed such that they are invariant to translation, rotation, and locally invariant to scale. Each match casts a vote on a certain object pose, rotation, scale, and position, and a joint estimate is found by a clustering procedure. The method is demonstrated on a number of real images and the region features are compared with the SIFT descriptor, which is another standard region feature for the same application. Finally, a new associative network is presented which applies the channel representation for both input and output data. This representation is sparse and monopolar, and is a simple yet powerful representation of scalars and vectors. It is especially suited for representation of several values simultaneously, a property that is inherited by the network and something which is useful in many computer vision problems. The chosen representation enables us to use a simple linear model for non-linear mappings. The linear model parameters are found by solving a least squares problem with a non-negative constraint, which gives a sparse regularized solution.
11
Forssʹen, Per-Erik. "Low and medium level vision using channel representations /." Linköping : Univ, 2004. http://www.bibl.liu.se/liupubl/disp/disp2004/tek858s.pdf.
Full text
12
Johansson, Björn. "Low level operations and learning in computer vision /." Linköping : Univ, 2004. http://www.bibl.liu.se/liupubl/disp/disp2004/tek912s.pdf.
Full text
13
Lim, Choon Kee. "Hypercube machine implementation of low-level vision algorithms." Ohio : Ohio University, 1989. http://www.ohiolink.edu/etd/view.cgi?ohiou1182864143.
Full text
14
McKinney, William Sigsbee. "A low cost vision system for landmark tracking." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/15943.
Full text
15
Daubney, Ben. "Using low-level motion for high-level vision." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508101.
Full text
16
Gavin, Andrew S. (Andrew Scott). "Low computation vision-based navigation for mobile robots." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/38006.
Full text
17
Forssén, Per-Erik. "Low and Medium Level Vision Using Channel Representations." Doctoral thesis, Linköpings universitet, Bildbehandling, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-24002.
Full textAbstract:
This thesis introduces and explores a new type of representation for low and medium level vision operations called channel representation. The channel representation is a more general way to represent information than e.g. as numerical values, since it allows incorporation of uncertainty, and simultaneous representation of several hypotheses. More importantly it also allows the representation of “no information” when no statement can be given. A channel representation of a scalar value is a vector of channel values, which are generated by passing the original scalar value through a set of kernel functions. The resultant representation is sparse and monopolar. The word sparse signifies that information is not necessarily present in all channels. On the contrary, most channel values will be zero. The word monopolar signifies that all channel values have the same sign, e.g. they are either positive or zero. A zero channel value denotes “no information”, and for non-zero values, the magnitude signifies the relevance. In the thesis, a framework for channel encoding and local decoding of scalar values is presented. Averaging in the channel representation is identified as a regularised sampling of a probability density function. A subsequent decoding is thus a mode estimation technique.' The mode estimation property of channel averaging is exploited in the channel smoothing technique for image noise removal. We introduce an improvement to channel smoothing, called alpha synthesis, which deals with the problem of jagged edges present in the original method. Channel smoothing with alpha synthesis is compared to mean-shift filtering, bilateral filtering, median filtering, and normalized averaging with favourable results. A fast and robust blob-feature extraction method for vector fields is developed. The method is also extended to cluster constant slopes instead of constant regions. The method is intended for view-based object recognition and wide baseline matching. It is demonstrated on a wide baseline matching problem. A sparse scale-space representation of lines and edges is implemented and described. The representation keeps line and edge statements separate, and ensures that they are localised by inhibition from coarser scales. The result is however still locally continuous, in contrast to non-max-suppression approaches, which introduce a binary threshold. The channel representation is well suited to learning, which is demonstrated by applying it in an associative network. An analysis of representational properties of associative networks using the channel representation is made. Finally, a reactive system design using the channel representation is proposed. The system is similar in idea to recursive Bayesian techniques using particle filters, but the present formulation allows learning using the associative networks.
18
Lim, Choon Kee. "Hypercube machine implementation of low-level vision algorithms." Ohio University / OhioLINK, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1182864143.
Full text
19
Sanata, Kelsey Ann. "Driving Exposure in Bioptic Drivers with Low Vision." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555451819437703.
Full text
20
Nadadur, Desikachari. "Noise covariance estimation in low-level computer vision /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/5988.
Full text
21
Cottini, Nicola. "Ultra-Low-Power Vision Systems for Wireless Applications." Doctoral thesis, Università degli studi di Trento, 2012. https://hdl.handle.net/11572/367662.
Full textAbstract:
Custom CMOS vision sensors could offer large opportunities for ultra-low power applications, introducing novel visual computation paradigms, aimed at closing the large gap between vision technology and energy-autonomous sensory systems. Energy-aware vision could offer new opportunities to all those applications, such as security, safety, environmental monitoring and many others, where communication infrastructures and power supply are not available or too expensive to be provided.
This thesis aims at demonstrating this concept, exploiting the potential of an energy-aware vision sensor, developed at FBK, that extracts the spatial contrast and delivers compressed data. As a case study, a custom stereo-vision algorithm has been developed, taking advantage of the sensor characteristics, targeted to a lower complexity and reduced memory with respect to a standard stereo-vision processing. Under specific conditions, the proposed approach has proven to be very promising, although much work has still to be done both at sensor and at processing levels.The last part of this thesis is focused on the improvement of the custom sensor. A novel vision sensor architecture has been developed, which is based on a proprietary algorithm, developed by a partner of FBK and targeted to surveillance applications. The algorithm is based on adaptive temporal contrast extraction and is very suitable to be implemented at chip level. Although the output of the algorithm has strong similarities with the spatial contrast vision sensor, it relies on temporal contrast rather than spatial one, which is much more robust for event detection applications. A first prototype of ultra-low power adaptive temporal contrast vision sensor has been developed and tested.
22
Cottini, Nicola. "Ultra-Low-Power Vision Systems for Wireless Applications." Doctoral thesis, University of Trento, 2012. http://eprints-phd.biblio.unitn.it/778/1/PhDThesisCottini.pdf.
Full textAbstract:
Custom CMOS vision sensors could offer large opportunities for ultra-low power applications, introducing novel visual computation paradigms, aimed at closing the large gap between vision technology and energy-autonomous sensory systems. Energy-aware vision could offer new opportunities to all those applications, such as security, safety, environmental monitoring and many others, where communication infrastructures and power supply are not available or too expensive to be provided.
This thesis aims at demonstrating this concept, exploiting the potential of an energy-aware vision sensor, developed at FBK, that extracts the spatial contrast and delivers compressed data. As a case study, a custom stereo-vision algorithm has been developed, taking advantage of the sensor characteristics, targeted to a lower complexity and reduced memory with respect to a standard stereo-vision processing. Under specific conditions, the proposed approach has proven to be very promising, although much work has still to be done both at sensor and at processing levels.The last part of this thesis is focused on the improvement of the custom sensor. A novel vision sensor architecture has been developed, which is based on a proprietary algorithm, developed by a partner of FBK and targeted to surveillance applications. The algorithm is based on adaptive temporal contrast extraction and is very suitable to be implemented at chip level. Although the output of the algorithm has strong similarities with the spatial contrast vision sensor, it relies on temporal contrast rather than spatial one, which is much more robust for event detection applications. A first prototype of ultra-low power adaptive temporal contrast vision sensor has been developed and tested.
23
Hopkins, Gregory Robert II. "Contrast sensitivity and vision-related quality of life assessment in the pediatric low vision population." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397751785.
Full text
24
Lindqvist, Susanne. "Vision and brain in adolescents with low birth weight." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for laboratoriemedisin, barne- og kvinnesykdommer, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-6612.
Full textAbstract:
Premature birth and pregnancy to term, but with intrauterine growth restriction (often manifesting as birth small for gestational age, SGA, at term), both represent suboptimal environments for the developing infant brain and eyes. Very low birth weight (VLBW, The aims of this study, which is part of large interdisciplinary follow up study also including cognitive, psychiatric, paediatric and motor evaluation, as well as cerebral MRI, was threefold: to examine differences in visual functions between adolescents with VLBW, or SGA at term, compared to an age matched control group to explore how detected impairments affect other functions (e.g. motor ability) to search for a cerebral correlate to the impaired visual functions, by using magnetic resonance diffusion tensor imaging (DTI). The study shows that the VLBW group was more likely to have poor visual acuity, reduced contrast sensitivity, poor convergence, strabismus, nystagmus, anisometropia, a need for new glasses and to have started with glasses earlier than the control group. The SGA group had a slight increase in hypermetropia, but did otherwise not differ from the control group. However, none of the participants were blind or had visual acuity Both the SGA and the VLBW group had increased risk for motor problems, but these were affected by visual ability only in the VLBW group. Risk for motor problems were reduced by 25 % by controlling for poor visual acuity, but group still remained a significant factor. Visual impairments may cause motor problems, but it is also possible that cerebral damage may be the cause of simultaneous visual and motor problems. Finally, using DTI, a positive correlation between visual acuity and the microstructure of white matter (reflecting axonal “healthiness”) was demonstrated in the splenium part of the corpus callosum. This part of the brain is responsible for the transhemispherical relay of visual data, and is particularly prone to injury in prematurity. However, it has not been regarded as an important factor for visual acuity in prematurity before. Premature infants are greatly at risk for perinatal cerebral injury, due to an extreme vulnerability of several cerebral systems at a crucial time, when development is particularly fast and comprehensive. This is combined with very poor ability to maintain homeostasis, causing them to suffer infections, hypoxia, unstable blood pressure, undernourishment, among others, all pathological conditions which affect the developing brain negatively. This study confirms that adolescents with VLBW have an increased risk of visual problems. Cerebral injury probably plays a major part in causing them.<br>Syn og hjerne hos ungdommer med lav fødselsvekt. Forhold i svangerskapet og rundt fødselen har betydning for hvor godt vi fungerer på en rekke områder senere i livet. Dette gjelder ikke minst synet. For å kartlegge hvordan det går med synet til barn som fødes meget for tidlig (de som veier under 1500 g ved fødsel) og barn som fødes til termin med lavere fødselsvekt enn det forventede på grunn av dårlig ernæring i svangerskapet, har vi undersøkt synet til 14-åringer i disse to gruppene. Ungdommer i samme alder født til termin med normal fødselsvekt utgjorde kontrollgruppe. Deltagerne i studien ble undersøkt av øyelege og fysioterapeut, og hjernens anatomi ble undersøkt med MR. Studien viser at det synsmessig kan gjøre stor forskjell mellom å veie mindre enn 1500 g ved fødselen og å være født til termin med normal fødselsvekt. I gruppen med for tidlig fødte ungdommer hadde nesten hver tredje dårligere syn enn det normale for alderen sammenlignet med bare 4 % i kontrollgruppen. Blant de premature var det flere som hadde nedsatt evne til å skjelne små forskjeller i kontrast, og det var også vanligere med skjeling og dårlig samsyn. Det var ikke større forekomst av nærsynthet eller langsynthet blant de premature. Derimot var det noe vanligere å trenge nye briller i prematurgruppen (53 %) enn i kontrollgruppen (34 %). Et oppløftende funn var at ingen av ungdommene var blind eller synshemmet etter Verdens Helseorganisasjons kriterier. Tenåringer i gruppen født til termin med lavere fødselsvekt enn det normale hadde ikke øket risiko for synsproblemer. Både de premature og ungdommene født til termin med lav fødselsvekt hadde økt forekomst av motoriske vansker. Da vi sammenlignet syn og motoriske evner, fant vi en sammenheng i prematurgruppen, men ikke i gruppen født til termin med lav fødselsvekt. Mange av disse problemene med syn og motorikk kan bero på skader i hjernen på grunn av den for tidlige fødselen. Vi sammenlignet hjernens anatomi med synsdata og fant at det i prematurgruppen var en sammenheng mellom syn og anatomisk struktur av den midtre hjernebjelken (”corpus callosum”) som knyter sammen de to hjernehalvdelene. Hjernebjelken er et område som er spesielt utsatt for skade hos premature, men det har tidligere ikke vært vist så tydelig at skade i dette området har betydning for synet. Dessuten fant vi en sammenheng mellom skade på andre deler av hjernens synsbaner og syn i prematurgruppen
25
Lu, Xiaoye. "Low-level computer vision applications to surveillance and robotics /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2007. http://uclibs.org/PID/11984.
Full text
26
Ryan, Barbara. "Evaluation of low vision services in the United Kingdom." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54233/.
Full textAbstract:
<bold>Chapter 6</bold> outlines an initial analysis of a database that was set up to enable clinical audit of the WLVS. The characteristics of those who used the service for the first time and how this changed as the service developed were investigated.
27
Lambert, Ben. "Integration of high and low-resolution aircraft vision systems." Thesis, University of Liverpool, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437517.
Full text
28
Njeru, Steve Murimi Mathenge. "Contrast Sensitivity and Visual Acuity in Low-Vision Students." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586966057072378.
Full text
29
Zuniga, Oscar A. "Low level and intermediate level vision in aerial images." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/54478.
Full textAbstract:
Low-level and intermediate-level computer vision tasks are regarded as transformations from lower to higher-level representations of the image information. An edge-based representation that makes explicit linear features and their spatial relationships is developed. Examples are presented in the scene domain of aerial images of urban scenes containing man-made structures.
The techniques used are based on a common structural and statistical model of the image data. This model assumes that the image data is adequately represented locally by a bivariate cubic polynomial plus additive independent Gaussian noise. This model, although simple, is shown to be useful for the design of effective computer vision solving tasks.
Four low-level computer vision modules are developed. First, a gradient operator which reduces sharply the gradient direction estimate bias that plagues current operators while also reducing sensitivity to noise. Secondly, a Bayes decision procedure for automatic gradient threshold selection that produces results which are superior to those obtained by the best subjective threshold. Thirdly, the new gradient operator and automatic gradient threshold selection are used in Haralick's directional zero-crossing edge operator resulting in improved performance. Finally, a graytone corner detector with significantly better probability of correct corner assignment than other corner detectors available in the literature.
Intermediate-level modules are developed for the construction of a number of intermediate level units from linear features. Among these is a linear segment extraction method that uses both, zero-crossing positional and angular information together with their distributional characteristics to accomplish optimal linear segment fitting. Methods for hypothesizing comers and relations of parallelism and collinearity among pairs of linear segments are developed. These relations are used to build higher-level groupings of linear segments that are likely to correspond to cultural objects.<br>Ph. D.
30
Gothwal, Vijaya K. "Development and validation of a questionnaire for assessment of functional vision performance in low vision children." Thesis, Queensland University of Technology, 2001. https://eprints.qut.edu.au/36770/1/36770_Digitised%20Thesis.pdf.
Full textAbstract:
BACKGROUND: The goal was to develop a reliable and valid questionnaire (the L V Prasad-Functional Vision Questionnaire, LVP-FVQ) to assess self-reported functional vision problems in day-day activities of school-going visually impaired children.
METHODS: Visually related activities of school-going children thought to be affected by any ocular disorder resulting in visual impairment were considered for the LVP-FVQ. A draft L VP-FVQ was developed from pilot work using focus group discussions and trials on a sample of 32 visually impaired children. The 20-item LVP-FVQ developed consisted of 19 items in 4 domains that related to day-day activities of school-going children. In addition, there was one question that asked children to rate their vision with respect to that of normally sighted friends. The 4 domains of the L VP-FVQ included: distance vision, near vision, colour vision and visual field. The 20-item L VP-FVQ was administered verbally to seventy-eight visually impaired Indian children aged 8-18 years with varying levels of vision loss from a range of ocular disorders. A subject's assessment of his/her ability to perform each task was scored on a 5-point Likert scale. Reliability testing included test-retest reliability (intraclass coefficient) and internal consistency reliability (Cronbach's alpha). Construct validation included consideration of the content validity, comparison with WHO categories of vision loss, and concurrent validity wherein the domain scores were compared with the clinical measures of vision. The last question that asked children to rate their vision with respect to that of normally sighted friends was also validated.
RESULTS: The 20-item LVP-FVQ was reduced to 14 items through item reduction. The last item was retained in the 14-item LVP-FVQ. The LVP-FVQ was easy to administer because it had a short test time and scoring was straightforward.
The test-retest reliability varied from 0.76 to 0.92 and internal consistency reliability varied from 0.29 to 0.76 for the 4 domains. However, internal consistency for all the 13 items of LVP-FVQ was high (0.84). A factor analysis with orthogonal varimax rotation of 13 items gave 4 factors: (i) visually demanding high contrast tasks, (ii) moderately visually difficult low contrast tasks, (iii) self-care and (iv) play activities, explaining the underlying dimensions to 66.2 percent. Of these, the first factor alone explained 35.1 percent of the variance in the LVP-FVQ score. The mean total LVP-FVQ scores were not significantly different for subjects with moderate low vision (visual acuity <6118-6/60 in the better eye) compared to those with severe vision loss ( <6/60-light perception), indicating that subjects in both these groups reported similar degrees of difficulty with their overall functional vision. However, multiple regression analysis revealed the best predictors of high contrast distance and near visual acuities were the responses to two items relating to copying from the blackboard and reading at arm's length.
CONCLUSIONS: The LVP-FVQ showed promising results as a reliable, valid and easily administered questionnaire to assess problems with functional vision in visually impaired children. Further refinement of the L VP-FVQ with additional items relevant to children with specific ocular disorders may increase its usefulness.
31
Bozeman, Laura Ann. "The fidelity of low vision simulator systems in clinical and functional settings /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
Full text
32
Amberson, Joshua James. "Staring Into the Sun: Essays on Vision and Blindness." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4457.
Full textAbstract:
This collection of essays is both a personal chronicle of vision loss and an investigation into the human eye. Delving into the history of corrective lenses, eye contact, crying, ocularcentrism, the typewriter, Mr. Magoo, and off-label drug use, these essays examine the wide variety of ways we relate to eyeballs, vision, and blindness.
33
Pihl, Johan. "An accessible grocery store for low vision customers : Human-centered design of a universal shopping solution, with a focus on people with low vision." Thesis, Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-69592.
Full textAbstract:
Around one percent of the Swedish population is defined as visually impaired and ten percent of them are classified as blind (Funka, n.d.; SRF, 2017a). A study shows that the prevalence of nearsightedness will increase to around half the population in the world in 2050 (Holden et. al., 2016). This suggests an increased need for solutions that work for people with reduced vision, not only for visually impaired but for a large group of the population. The aim of the project is to conceptualize a technological mainstream solution that supports people when shopping for groceries. The focus is on making this solution accessible for people with low vision. The project was planned based on the human-centered design process described by IDEO.org (2015), with an overall process divided into three phases: inspiration, ideation, and implementation. In the first phase, inspiration, a literature review was done, different field studies and other research methods were carried out. The outcome of the phase was three personas, two scenarios, and a design specification. During the second phase, ideation, the project scope was narrowed down – focusing on physical grocery stores (excluding online stores) and on conceptualizing a smartphone application. An ideation workshop was conducted, followed by concept creation, paper prototyping, scenario writing, user evaluations and a final concept selection. In the last phase, implementation, follow up feedback sessions were held and a simulation test of the final concept was held. Visualizations and presentation of the final concept were done. A list of summarized design principles was created, as support for further work on designing the application for low vision users. The final concept is based on a smartphone application that supports the customer through shopping list management, aisle navigation, item selection and item scanning, for a seamless customer experience for both people with full and low vision. The technology that will be utilized is Pricer AB's electronic shelf labels (ESL) with item positioning, customer navigation, and individual flashing light, combined with the grocery store online database with item descriptions and images. Here follows an example of how the interaction could look like for someone with low vision: He always prepares his shopping list before heading to the store, this way he knows the shopping will be easier for him. In the store, he gets all items on the list presented in the correct order of the store, in that way he knows what to search for. When looking for soy sauce from his shopping list he has trouble remembering where the section is, so he checks it up with the navigation. He realizes that it was just around the corner of where he just passed by. Once at the section he is presented with a list of different soy sauces in the application, matching his location, previous purchases and the soy sauce on his shopping list. He can now select the one that he prefers, and a picture of it appears on the screen, simultaneously a flashing green light appears by the item on the shelf, and he can easily and independently find the way right up to the soy sauce he wants.<br>Ungefär en procent av Sveriges befolkning är synskadade, och tio procent av dem är så pass gravt synskadade att de kan definieras som blinda (Funka, n.d.; SRF, 2017a). Enligt en studie förväntas närsynthet världen över att öka, och under 2050 vara uppe i hälften av jordens befolkning (Holden et. al., 2016). Detta tyder på ett ökat behov av lösningar som fungerar för personer med nedsatt syn, inte bara för synskadade utan för en stor del av befolkningen. Målet med projektet är att undersöka nuläget och behoven för synsvaga personer när de handlar mat, för att sedan kunna utveckla universell teknisk lösning som ska fungera som ett stöd när man handlar mat. Projektet planerades utifrån en människocentrerad designprocess beskriven av IDEO.org (2015), som är indelad i tre faser: inspiration, idégenereringen och genomförande. I den första fasen, inspiration, gjordes en litteraturstudie, flera fältstudier genomfördes, samt andra research metoder. Resultatet här var tre personas, två scenarion och en designspecifikation. Under den andra fasen, idégenereringen, ställdes nya avgränsningar upp för projektet – fokuset riktades nu mot den fysiska butiker (avgränsning från e-handeln) och att målet skulle vara att ta fram en smartphone-applikation. En idéworkshop genomfördes, konceptgenerering, skapande av pappersprototyper, scenarion, utvärdering med användare och ett slutligt konceptval. I sista fasen, genomförande, följdes det slutliga konceptet upp med tidigare deltagare och det slutliga konceptet testades i en simulerad studie. Visualisering och presentation av slutkonceptet gjordes. Designprinciper för utveckling av applikationer för synsvaga sammanfattades, för att fungera som stöd för vidare arbete med utveckling av konceptet. Slutkonceptet bygger på en smartphone-applikation som ska fungera som stöd för kunden, från skapandet av inköpslista, navigering i butiken, val och identifiering av varor och slutligen att scanna varan. I sin helhet skapar detta en komplett lösning i mataffären för både seende och synsvaga kunder. Tekniken som ska utnyttjas för konceptet är Pricer AB's elektroniska hyllkantsetikett-system (ESL-system) med positionering, kundnavigering samt en lysdiod på varje enskild etikett, i kombination med butikens online-databas med produktbeskrivningar och bilder på varorna. Här kommer en beskrivning av hur interaktionen med systemet kan gå till för någon som är synsvag: Han förbereder alltid sin inköpslista innan han går till affärer, eftersom han vet att det underlättar för honom. Väl i butiken får han varorna från inköpslistan presenterade i den ordningen de kommer, vilket förenklar letandeprocessen. När han letar efter sojasås som han har på listan har han svårt att komma ihåg var i butiken han hittar den, så han kollar upp det med navigeringsfunktionen. Han inser då att han missade den just bakom hörnet som han gick förbi. Väl framme vid sektionen får han en lista med olika sojasåser presenterade i applikationen, de baseras på hans position i butiken, tidigare köp och vad han har på inköpslistan. Han kan nu välja den han gillar och får då en bild på varan på sin skärm, samtidigt som en grön lampa blinkar precis där varan är placerad på hyllan. Han kan nu enkelt och självständigt plocka varan han vill ha från hyllan.
34
Early, Frances. "Low level visual processing in ageing and dementia." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238159.
Full text
35
Taylor, Cynthia Lorene Newby Marilyn Provart Rennels Max R. "A visual processing art program for low vision older adults." Normal, Ill. Illinois State University, 1989. http://wwwlib.umi.com/cr/ilstu/fullcit?p8918627.
Full textAbstract:
Thesis (Ed. D.)--Illinois State University, 1989.<br>Title from title page screen, viewed October 13, 2005. Dissertation Committee: Marilyn Newby, Max R. Rennels (co-chairs), Evelyn Rex, Robert Stefl. Includes bibliographical references (leaves 68-72) and abstract. Also available in print.
36
Murali, Vidya N. "Autonomous navigation and mapping using monocular low-resolution grayscale vision." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1219852130/.
Full text
37
Jessa, Zahra. "Improving the detection of correctable low vision in older people." Thesis, City University London, 2009. http://openaccess.city.ac.uk/12443/.
Full textAbstract:
In the UK, 20-50% of older people have undetected reduced vision and in most of these cases the poor vision can be readily corrected by new spectacles and/or cataract surgery. It is often assumed that older people with vision loss will have regular eye examinations so that these problems can be detected, but for many older people this assumption is wrong. One approach to improving the take-up of eyecare services is to carry out vision screening of older people in the community to raise awareness of the need for professional eyecare. The present study aimed to investigate which tests would be most appropriate to screen for correctable visual loss in the older population and to incorporate these tests in a screening tool that would be effective yet simple to administer. The present research sought to investigate whether computerised techniques would be an effective method to screen vision in older people. In Study 1, a computerised vision screener was used to test 180 older people in South London. All participants also received a full, ‘gold standard’, eye examination. Significant cataract was present in 32%, correctable refractive error in 39%, and overall 58% had at least one of these forms of correctable visual problems. The computerised vision screener was able to detect these conditions in about 80% of cases. In Study 2, 200 participants were screened using a revised version of the computerised vision screener. A new flipchart vision screener including the main tests from the computer vision screener was also investigated. 31% of participants in Study 2 had significant cataracts, 30% had correctable refractive errors, and 51% had at least one of these conditions. The computer screener and flipchart tool were both good at detecting significant cataract and refractive errors. About 80% of cases of visual loss due to these problems or due to AMD could be detected with either of the screening tools. Using a pragmatic operational criterion, the screening tools detect about 94% of cases who might be considered by an optometrist to be in need of an eye examination (either overdue or reduced visual acuity). Glaucoma is a difficult disease to diagnose and it was found, as expected, that neither screening instrument was very good at detecting glaucoma. The results showed that the best single test to use for screening of visual loss is HCVA which provides both a high sensitivity (77%) and specificity (73%). Greater sensitivity (80%) is achieved when high contract acuity, low contrast acuity and near acuity are used in combination. Greater specificity (77%) can be achieved by using low contrast acuity alone. It is concluded that vision screening does not replace the need for professional eyecare, but acts as a tool to better inform the public of the need for regular eyecare.
38
Kaufmann, Jan [Verfasser]. "VEP-basierte objektive Visusbestimmung im Low-Vision-Bereich / Jan Kaufmann." Magdeburg : Universitätsbibliothek, 2016. http://d-nb.info/1105554724/34.
Full text
39
Wiecek, E. K. "Quantifying functional impairment and metamorphopsia in a low vision population." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1460419/.
Full textAbstract:
Visual perception is required to interact with our environment on a daily basis. Pathological vision loss can disrupt perception and cause systematic functional changes. Quantifying these changes is essential to monitor deficits associated with visual disease, but measurement is complicated by retinotopic impairment, an overlap of symptoms, and influence from higher visual processes. Visual search provides a way to examine visual functioning in a ubiquitous task that involves an interplay between high-resolution central vision and low-resolution peripheral vision. We examined visual search performance in 12 participants with peripheral visual field loss (PVFL) and eight participants with central visual field loss (CVFL). Visual search behavior in PVFL participants was significantly different from age-matched controls with no field loss; yet oculomotor parameters were not significantly different. This suggests that PVFL impairs eye movement strategies, but not dynamics of oculomotor control. CVFL participants completed a visual search task with a set of image modifications designed to improve common perceptual deficits of CVFL patients. There was no significant benefit of image modification on performance, but a multivariate model accurately predicted performance on the basis of age, acuity and extent of field loss. Attempts to improve search may be more successful if they are tailored to the individual’s deficits. Metamorphopsia (visual distortion) often precedes visual field loss, may be caused by retinal layer displacement, and can be used to study the progression of retinal disease. A retrospective study of more than 7,000 Amsler grids showed systematic variations in the spatial pattern of distortion across different etiologies and concluded that metamorphopsia is a prevalent symptom that varies across disease type. However, a study of patient reported outcomes determined that metamorphopsia is under-reported in retinal disease patients, which may impact self-referral and clinical management. We also developed novel psychophysical methods to quantify metamorphopsia, yet found that measures across methods were uncorrelated. This suggests that metamorphopsia is not simply a consequence of pathological retinal displacement, but involves higher visual processes. Finally, we considered how metamorphopsia interacts with visual acuity and found a nonlinear relationship between the spatial properties of distortion and performance on a letter recognition task.
40
Volonakis, Timothy Nik. "Using low-level vision principles towards a surrogate human observer." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.705478.
Full text
41
Pemula, Latha. "Low-shot Visual Recognition." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/73321.
Full textAbstract:
Many real world datasets are characterized by having a long tailed distribution, with several samples for some classes and only a few samples for other classes. While many Deep Learning based solutions exist for object recognition when hundreds of samples are available, there are not many solutions for the case when there are only a few samples available per class. Recognition in the regime where the number of training samples available for each class are low, ranging from 1 to couple of tens of examples is called Lowshot Recognition. In this work, we attempt to solve this problem. Our framework is similar to [1]. We use a related dataset with sufficient number (a couple of hundred) of samples per class to learn representations using a Convolutional Neural Network (CNN). This CNN is used to extract features of the lowshot samples and learn a classifier . During representation learning, we enforce the learnt representations to obey certain property by using a custom loss function. We believe that when the lowshot sample obey this property the classification step becomes easier. We show that the proposed solution performs better than the softmax classifier by a good margin.<br>Master of Science
42
Alnestig, Henrik. "On the Feasibility of Low Cost Computer Vision : Building and Testing SimpleEye." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-29363.
Full textAbstract:
This thesis explores a novel approach to the computer vision eld in the form of lowcost computer vision intended for industrial use. The system proposed in this thesis, calledSimpleEye, is implemented and tested against an existing system. Dierent approachesto object detection and data extraction from a scene, as well as common applications ofcomputer vision in the industry, are examined. Three algorithms are implemented, aimedat dierent industrial applications. These are two types of object recognition, using CannyEdge detection and connected-component labeling, as well as barcode scanning. The tests,each targeting one of the implemented approaches, show promising results for low costcomputer vision. While the system is expectedly lacking in speed, it has no diculties inachieving good result in applications which are not highly time critical. SimpleEye yieldedaccuracy and precision comparable to commercial systems, with parts costing approximately100 USD. The tests show that the system is able to function in several computer visionapplications used today, including visual servoing, blob detection, blob tracking, and barcodescanning.
43
Cheong, Allen Ming Yan. "Reading performance with stand magnifiers in age-related macular degeration." Thesis, Queensland University of Technology, 2003. https://eprints.qut.edu.au/15870/1/Allen_Cheong_Thesis.pdf.
Full textAbstract:
This research was designed to address important issues for the effective prescription of, and training in the use of, magnifiers for reading patients with visual impairment. The emphasis was on the development of simple methods of assessment and training that could be easily implemented, at no great cost, by low vision practitioners in clinical practice. To ensure that the results would be widely applicable, the research focused on subjects with age-related macular degeneration (AMD) using stand magnifiers (being the most common cause of low vision and the most commonly prescribed magnifiers respectively). From this research, modifications to the current methods of reading rehabilitation are suggested to more effectively improve low vision reading for the millions of people with low vision around the world. The magnification and reading performance achieved with the magnifier determined by the fixed acuity reserve method was as valid as that achieved with the magnifier determined by the individual acuity reserve method. The fixed acuity reserve is a simpler method to calculate the required magnification, as it requires only near visual acuity and the patient's goal reading task. This method was primarily used to select the appropriate illuminated stand magnifiers for the subjects participating in the subsequent studies and is recommended for use as the starting point in clinical low vision practice.
The main study of this thesis was a longitudinal investigation of the benefit of large print reading practice on reading performance with stand magnifiers. Instead of the intensive training programs on magnifier use which have been suggested by previous studies, this study aimed to investigate the effect of simple large print reading practice, under either full or restricted field of view (the latter simulated by a practice stand), on reading rate with stand magnifiers for subjects with AMD. The experimental hypothesis was that reading practice prior to the prescription of stand magnifiers would improve reading performance with the stand magnifiers for subjects with AMD. As previous studies have shown, reading rate reduced when a stand magnifier was first introduced. One week of reading practice on large print, with or without a reduced field of view, gave an improvement in reading rate with the stand magnifier for passages of text (such that the reading rates with and without magnifiers were not significantly different). There was a suggestion that this practice may give a more rapid improvement in reading rate than that achieved by the control subjects who did not do any large print reading practice, but this did not reach statistical significance. Even very brief reading with the stand magnifiers by the control subjects gave some improvement in reading rate. Therefore, home or in-office reading practice on large print or with magnifiers is recommended for patients with AMD before magnifiers are prescribed.
Subjects who had neither reading practice nor exposure to the magnifier prior to its prescription required two weeks practice using their stand magnifiers to achieve their maximum reading rate. This suggests that home practice in using stand magnifiers is beneficial and a follow up visit is recommended two weeks after the provision of a magnifier to assess any change in reading rate. If no improvement in the magnifier reading rate is found or the rate is less than the reading rate on large print without a magnifier, further investigations of the patients' vision and/or their magnifier manipulation strategy are necessary.
In the last study, a simple method aimed at alleviating difficulties with magnifier manipulation and navigation, the attachment of a line guide to the base of the stand magnifier, was investigated using both objective methods (recording magnifier movements and reading rate measures) and subjective methods (simple questionnaire). Although there was no improvement in the objective measures of reading or navigation performance with the line guide, more than half of the subjects with low vision preferred to have the line guide on their stand magnifiers. This suggests that the objective measures might not be sensitive enough to predict the subjective response, or that other factors that were not measured in this study influenced subjects' preferences in selecting the line guide (e.g., psychological support provided by the line guide in reading orientation). Clinically, the subjective response of patients to the use of low vision aids as well as their motivation are important criteria for success in low vision rehabilitation. There was a tendency for less experienced users to prefer the line guide to assist their use of the stand magnifier for reading. Therefore, a line guide could be offered as a preliminary training aid when stand magnifiers are first prescribed for AMD patients. Possible improvements to the design of the line guide were identified. Further research is required to assess the benefits of this or similar devices for new magnifier users and to understand the difficulties that people with visual impairment have with page navigation in order to determine improved methods of training navigation strategies.
The unique contribution of this study to the field of low vision rehabilitation is that the benefit of short-term reading practice, on large print or with magnifiers, as simple, cheap methods of enhancing reading performance with stand magnifiers was demonstrated. The results of this study have led to the development of recommendations for assessing and training AMD patients who are prescribed stand magnifiers.
44
Cheong, Allen Ming Yan. "Reading performance with stand magnifiers in age-related macular degeration." Queensland University of Technology, 2003. http://eprints.qut.edu.au/15870/.
Full textAbstract:
This research was designed to address important issues for the effective prescription of, and training in the use of, magnifiers for reading patients with visual impairment. The emphasis was on the development of simple methods of assessment and training that could be easily implemented, at no great cost, by low vision practitioners in clinical practice. To ensure that the results would be widely applicable, the research focused on subjects with age-related macular degeneration (AMD) using stand magnifiers (being the most common cause of low vision and the most commonly prescribed magnifiers respectively). From this research, modifications to the current methods of reading rehabilitation are suggested to more effectively improve low vision reading for the millions of people with low vision around the world. The magnification and reading performance achieved with the magnifier determined by the fixed acuity reserve method was as valid as that achieved with the magnifier determined by the individual acuity reserve method. The fixed acuity reserve is a simpler method to calculate the required magnification, as it requires only near visual acuity and the patient's goal reading task. This method was primarily used to select the appropriate illuminated stand magnifiers for the subjects participating in the subsequent studies and is recommended for use as the starting point in clinical low vision practice.
The main study of this thesis was a longitudinal investigation of the benefit of large print reading practice on reading performance with stand magnifiers. Instead of the intensive training programs on magnifier use which have been suggested by previous studies, this study aimed to investigate the effect of simple large print reading practice, under either full or restricted field of view (the latter simulated by a practice stand), on reading rate with stand magnifiers for subjects with AMD. The experimental hypothesis was that reading practice prior to the prescription of stand magnifiers would improve reading performance with the stand magnifiers for subjects with AMD. As previous studies have shown, reading rate reduced when a stand magnifier was first introduced. One week of reading practice on large print, with or without a reduced field of view, gave an improvement in reading rate with the stand magnifier for passages of text (such that the reading rates with and without magnifiers were not significantly different). There was a suggestion that this practice may give a more rapid improvement in reading rate than that achieved by the control subjects who did not do any large print reading practice, but this did not reach statistical significance. Even very brief reading with the stand magnifiers by the control subjects gave some improvement in reading rate. Therefore, home or in-office reading practice on large print or with magnifiers is recommended for patients with AMD before magnifiers are prescribed.
Subjects who had neither reading practice nor exposure to the magnifier prior to its prescription required two weeks practice using their stand magnifiers to achieve their maximum reading rate. This suggests that home practice in using stand magnifiers is beneficial and a follow up visit is recommended two weeks after the provision of a magnifier to assess any change in reading rate. If no improvement in the magnifier reading rate is found or the rate is less than the reading rate on large print without a magnifier, further investigations of the patients' vision and/or their magnifier manipulation strategy are necessary.
In the last study, a simple method aimed at alleviating difficulties with magnifier manipulation and navigation, the attachment of a line guide to the base of the stand magnifier, was investigated using both objective methods (recording magnifier movements and reading rate measures) and subjective methods (simple questionnaire). Although there was no improvement in the objective measures of reading or navigation performance with the line guide, more than half of the subjects with low vision preferred to have the line guide on their stand magnifiers. This suggests that the objective measures might not be sensitive enough to predict the subjective response, or that other factors that were not measured in this study influenced subjects' preferences in selecting the line guide (e.g., psychological support provided by the line guide in reading orientation). Clinically, the subjective response of patients to the use of low vision aids as well as their motivation are important criteria for success in low vision rehabilitation. There was a tendency for less experienced users to prefer the line guide to assist their use of the stand magnifier for reading. Therefore, a line guide could be offered as a preliminary training aid when stand magnifiers are first prescribed for AMD patients. Possible improvements to the design of the line guide were identified. Further research is required to assess the benefits of this or similar devices for new magnifier users and to understand the difficulties that people with visual impairment have with page navigation in order to determine improved methods of training navigation strategies.
The unique contribution of this study to the field of low vision rehabilitation is that the benefit of short-term reading practice, on large print or with magnifiers, as simple, cheap methods of enhancing reading performance with stand magnifiers was demonstrated. The results of this study have led to the development of recommendations for assessing and training AMD patients who are prescribed stand magnifiers.
45
Senlet, Turgay. "Vision Based Obstacle Detection And Avoidance Using Low Level Image Features." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607229/index.pdf.
Full textAbstract:
This study proposes a new method for obstacle detection and avoidance using low-level MPEG-7 visual descriptors. The method includes training a neural network with a subset of MPEG-7 visual descriptors extracted from outdoor scenes. The trained neural network is then used to estimate the obstacle presence in real outdoor videos and to perform obstacle avoidance. In our proposed method, obstacle avoidance solely depends on the estimated obstacle
presence data.
In this study, backpropagation algorithm on multi-layer perceptron neural network is utilized as a feature learning method. MPEG-7 visual descriptors are used to describe basic features of the given scene image and by further processing these features, input data for the neural network is obtained.
The learning/training phase is carried out on specially constructed synthetic video sequence with known obstacles. Validation and tests of the algorithms are performed on actual outdoor videos. Tests on indoor videos are also performed to evaluate the performance of the proposed algorithms in indoor scenes.
Throughout the study, OdBot 2 robot platform, which has been developed by the author, is used as reference platform.
For final testing of the obstacle detection and avoidance algorithms, simulation environment is used.
From the simulation results and tests performed on video sequences, it can be concluded that the proposed obstacle detection and avoidance methods are robust against visual changes in the environment that are common to most of the outdoor videos. Findings concerning the used methods are presented and discussed as an outcome of this study.
46
Andersson, Mats T. "Controllable Multi-dimensional Filters and Models in Low-Level Computer Vision." Doctoral thesis, Linköpings universitet, Bildbehandling, 1992. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-54340.
Full textAbstract:
This thesis concerns robust estimation of low-level features for use in computer vision systems. The presentation consists of two parts. The first part deals with controllable filters and models. A basis filter set is introduced which supports a computationally efficient synthesis of filters in arbitrary orientations. In contrast to many earlier methods, this approach allows the use of more complex models at an early stage of the processing. A new algorithm for robust estimation of orientation is presented. The algorithm is based on synthesized quadrature responses and supports the simultaneous representation and individual averaging of multiple events. These models are then extended to include estimation and representation of more complex image primitives such as as line ends, T-junctions, crossing lines and curvature. The proposed models are based on symmetry properties in the Fourier domain as well as in the spatial plane and the feature extraction is performed by applying the original basis filters directly on the grey-level image. The basis filters and interpolation scheme are finally generalized to allow synthesis of 3-D filters. The performance of the proposed models and algorithms is demonstrated using test images of both synthetic and real world data. The second part of the thesis concerns an image feature representation adapted for a robust analogue implementation. A possible use for this approach is in analogue VLSI or corresponding analogue hardware adapted for neural networks. The methods are based on projections of quadrature filter responses and mutual inhibition of magnitude signals.
47
Assal, Mohamed Helmy Anwar Mohamed. "A study of low level vision algorithms in bar code recognition." Thesis, University of Kent, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328035.
Full text
48
Everingham, Mark Richard. "Methods and metrics for image classification with application to low vision." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394067.
Full text
49
Spaeth, Mark Christian 1974. "A low-cost hybrid vision system for intelligent cruise control applications." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/16728.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.<br>Includes bibliographical references (p. 95-96).<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>In recent years, automobiles have become increasingly computerized and varying degrees of intelligent control has been integrated into automotive systems. A natural extension of this trend is full intelligent and autonomous control of vehicle by onboard computer systems. This thesis presents the design, development, and construction of a low-cost, low-power vision system suitable for on-board automated vehicle systems such as intelligent cruise control. The apparatus leverages vision algorithms, simplified by a prescribed camera geometry, to compute depth maps in real-time, given the input from three imagers mounted on the vehicle. The early vision algorithms are implemented using Dr. David Martin's ADAP mixed signal array processor. The back-end algorithms are mplemented in software on PC for simplicity, but could easily be implemented in hardware in a later design. The final apparatus was able to compute depth maps at a rate of 24 frames per second, limited only by the interrupt latency of the PC executing the algorithms.<br>by Mark Christian Spaeth.<br>S.M.
50
Gibson, David Peter. "The application of computer vision to very low bit-rate communications." Thesis, University of Bristol, 2000. http://hdl.handle.net/1983/eed65e91-0b05-4130-8c92-6cdf34b66150.
Full text