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IMAGE ENHANCEMENT FOR IMPAIRED VISION: THE CHALLENGE OF EVALUATION
"... With the aging of the population, the prevalence of eye diseases and thus of vision impairment is increasing. The TV watching habits of people with vision impairments are comparable to normally sighted people, 1 however their vision loss prevents them from fully benefiting from this medium. For over ..."
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With the aging of the population, the prevalence of eye diseases and thus of vision impairment is increasing. The TV watching habits of people with vision impairments are comparable to normally sighted people, 1 however their vision loss prevents them from fully benefiting from this medium. For over 20 years we have been developing video image-enhancement techniques designed to assist people with visual impairments, particularly those due to central retinal vision loss. A major difficulty in this endeavor is the lack of evaluation techniques to assess and compare the effectiveness of various enhancement methods. This paper reviews our approaches to image enhancement and the results we have obtained, with special emphasis on the difficulties encountered in the evaluation of the benefits of enhancement and the solutions we have developed to date.
Statistical analysis of subjective preferences for video enhancement
- in Human Vision and Electronic Imaging XV 7527, 75270E
, 2010
"... ABSTRACT Traditional Thurstone scaling (1927) constructs a perceptual scale from pairwise comparisons without providing statistical inferences. We show that subjective preferences for moving video using pairwise comparisons can be analyzed to construct a perceptual scale and provide the statistical ..."
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ABSTRACT Traditional Thurstone scaling (1927) constructs a perceptual scale from pairwise comparisons without providing statistical inferences. We show that subjective preferences for moving video using pairwise comparisons can be analyzed to construct a perceptual scale and provide the statistical significance of preference differences. Two statistical methods (binary logistic regression and linear regression) are described. Data sets from two studies are used to demonstrate the perceptual scale construction from the traditional Thurstone method and from the described statistical methods. Both the studies showed videos on two side-by-side TVs. Four enhancement levels (Off, Low, Medium and High) were applied to the videos using a commercial device. Subjects made pairwise comparisons to indicate their preference of one video over another. The perceptual scales constructed from the three methods were comparable, except when there were cells missing from the preference matrix. Binary logistic regression easily permitted modeling of additional factors, such as side bias. Video quality can be systematically assessed using pairwise comparisons and statistical methods that permits construction of a perceptual scale and provide statistical significance for the compared levels.
8.2 / P.Satgunam 8.2: Factors Affecting Image Quality Preferences
"... Image quality plays a key role in consumer purchasing decisions. In this study we manipulated image quality of videos using a consumer product that enhances digital video images in real time. Videos were presented on two HDTVs, enhanced by varying amounts and subjects made pairwise comparisons. Our ..."
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Image quality plays a key role in consumer purchasing decisions. In this study we manipulated image quality of videos using a consumer product that enhances digital video images in real time. Videos were presented on two HDTVs, enhanced by varying amounts and subjects made pairwise comparisons. Our results showed two distinct preference groups (“Sharp ” and “Smooth”) in our study subjects. Preferences for enhancement depended on the video content, particularly the presence or absence of a human face. 1.
Ophthalmic & Physiological Optics ISSN 0275-5408 Television, computer and portable display device use by people with central vision impairment
, 2011
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Copyright © 2012 American Academy of Optometry ORIGINAL ARTICLE Torsional Anomalous Retinal Correspondence Effectively Expands the Visual Field
"... Purpose. Exotropia in congenital homonymous hemianopia has been reported to provide field expansion that is more useful when accompanied with harmonious anomalous retinal correspondence (HARC). Torsional strabismus with HARC provides a similar functional advantage. In a subject with hemianopia demon ..."
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Purpose. Exotropia in congenital homonymous hemianopia has been reported to provide field expansion that is more useful when accompanied with harmonious anomalous retinal correspondence (HARC). Torsional strabismus with HARC provides a similar functional advantage. In a subject with hemianopia demonstrating a field expansion consistent with torsion, we documented torsional strabismus and torsional HARC. Methods. Monocular visual fields under binocular fixation conditions were plotted using a custom dichoptic visual field perimeter. The dichoptic visual field was also modified to measure perceived visual directions under dissociated and associated conditions across the central 50 ° diameter field. The field expansion and retinal correspondence of a subject with torsional strabismus (along with exotropia and right hypertropia) with congenital homonymous hemianopia was compared with that of another exotropic subject with acquired homonymous hemianopia without torsion and to a control subject with minimal phoria. Torsional rotations of the eyes were calculated from fundus photographs and perimetry. Results. Torsional anomalous retinal correspondence documented in the subject with congenital homonymous hemianopia provided a functional binocular field expansion up to 18°. Normal retinal correspondence was mapped for the full 50 ° visual field in the control subject and for the seeing field of the acquired homonymous hemianopia subject, limiting the functional field expansion benefit.
OPTOMETRY AND VISION SCIENCE Copyright © 2012 American Academy of Optometry ORIGINAL ARTICLE Volume Perimetry: Measurement in Depth of
"... Purpose. Volume scotomas are three-dimensional regions of space that are not visible to the observer. Volume perimetry maps volume scotomas. Volume scotomas predicted from combining monocular visual fields assume known fixation locus (mainly foveal). However, fixation loci are not always known, espe ..."
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Purpose. Volume scotomas are three-dimensional regions of space that are not visible to the observer. Volume perimetry maps volume scotomas. Volume scotomas predicted from combining monocular visual fields assume known fixation locus (mainly foveal). However, fixation loci are not always known, especially with central field loss (CFL). Here we demonstrate methods for measuring and calculating volume scotomas and discuss their practical implications. Methods. Three patients (bitemporal hemianopia, binasal scotoma, and CFL) were evaluated. Slices through the volume scotomas were measured at three distances: at the plane of fixation, at a plane anterior to fixation (representing anterior volume perimetry), and at a plane posterior to fixation (representing posterior volume perimetry). For anterior volume perimetry, patients fixated on a screen 100 cm away through a beamsplitter that reflected the perimetric stimulus (at 50 cm). For posterior volume perimetry, patients fixated on a near target (50 cm), while perimetric stimuli were presented on a screen 150 cm beyond fixation. At the plane of fixation, monocular visual fields under binocular viewing conditions were measured using a computerized dichoptic perimeter. Results. Posterior and anterior volume scotomas were documented in patients with bitemporal hemianopia and binasal scotomas, respectively. The CFL patient demonstrated both anterior and posterior volume scotomas. Scotoma magnitude was considered to determine its effect on visual function.
