No / The purpose of this article is to determine whether blur adaptation influences blur sensitivity and blur discrimination thresholds in young adult myopes and emmetropes. In addition, to determine whether there is a differential effect of blur adaptation on blur sensitivity and discrimination between refractive error groups. Proximal and distal blur sensitivity thresholds and blur discrimination thresholds were measured under cycloplegia with a Badal optometer in 24 young adult subjects (8 emmetropes [EMM], 8 early-onset myopes [EOM], and 8 late-onset myopes [LOM]). Adaptation to 1 D of myopic refractive blur was then undertaken for 30 minutes. Blur sensitivity and discrimination thresholds were then remeasured. After blur adaptation, blur sensitivity, and blur discrimination thresholds were found to be elevated. Blur adaptation had a significant effect on distal blur sensitivity threshold, with the largest effect being observed in the EOMs. Mean changes in distal blur sensitivity thresholds were EMMs +0.03 ± 0.14 D, EOMs +0.30 ± 0.21 D, and LOMs +0.08 ± 0.13 D. Adaptation to a degraded stimulus modifies the blur detection mechanisms of the visual system in young adults. Depth of focus is expanded by prolonged exposure to defocus. EOMs are more susceptible to this phenomenon than are LOMs and EMMs.

Yes / Blur is one of the most commonly reported visual symptoms of glaucoma, but it is not directly measured by current clinical tests. We aimed to investigate the effects of glaucoma on detection and discrimination of image blur. People with glaucoma, separated into two groups with (n=15) or without (n=17) central visual field defects measured by 10-2 perimetry, and an age-similar control group (n=18) participated. First, we measured contrast detection thresholds centrally using a 2-interval forced choice procedure. We then measured blur detection and discrimination thresholds for the same stimuli (reference blurs 0, 1 arcmin respectively) using a 2-alternative forced choice procedure under two contrast conditions; 4x individual detection threshold for the low contrast condition, 95% contrast for the high contrast condition. The stimulus was a horizontal edge bisecting a hard-edged circle of 4.5° diameter. Data were analysed by linear mixed modelling. Contrast detection thresholds for the glaucoma group with central visual field defects were raised by 0.014 ± 0.004 (mean ± SE, Michelson units) (p=0.002) and by 0.011 ± 0.004 (p=0.03) relative to control and glaucoma without central visual field defect groups respectively. Blur detection and discrimination thresholds were similar between groups, with small elevations in blur detection thresholds in the glaucoma groups not reaching statistical significance (detection p=0.29, discrimination p=0.91). The lower contrast level increased thresholds from the higher contrast level by 1.30 ± 0.10 arcmin (p<0.001) and 1.05 ± 0.096 arcmin (p<0.001) for blur detection and discrimination thresholds respectively. Early-moderate glaucoma resulted in only minimal elevations of blur detection thresholds that did not reach statistical significance in this study. Despite the prevalence of blur as a visual symptom of glaucoma, psychophysical measurements of blur detection or discrimination may not be good candidates for development as clinical tests for glaucoma / College of Optometrists PhD scholarship

Motion blur is one important method for increasing the visual quality of real-time applications. This is increasingly true in the area of interactive applications, where designers often seek to add graphical flair or realism to their programs. These applications often have animated characters with a polygonal mesh wrapped around an animated skeleton; and as the skeleton moves the mesh deforms with it. This thesis presents a method for adding a geometric motion blur to a deforming polygonal mesh. The scheme presented tracks an object's motion silhouette, and uses this to create a polygonal mesh. When this mesh is added to the scene, it gives the appearance of a motion blur on a single object or particular character. The method is generic enough to work on nearly any type of moving polygonal model. Examples are given that show how the method could be expanded and how changes could be made to improve its performance.

Motion blur is one important method for increasing the visual quality of real-time applications. This is increasingly true in the area of interactive applications, where designers often seek to add graphical flair or realism to their programs. These applications often have animated characters with a polygonal mesh wrapped around an animated skeleton; and as the skeleton moves the mesh deforms with it. This thesis presents a method for adding a geometric motion blur to a deforming polygonal mesh. The scheme presented tracks an object's motion silhouette, and uses this to create a polygonal mesh. When this mesh is added to the scene, it gives the appearance of a motion blur on a single object or particular character. The method is generic enough to work on nearly any type of moving polygonal model. Examples are given that show how the method could be expanded and how changes could be made to improve its performance.

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Retinal blur experienced by myopes during near work has been linked to myopia development and progression. Whether poor responses to blur signals are due to poor perceptual blur sensitivity (subjective depth of focus), poor neural accommodation responses (objective depth of focus) to blur or optical differences such as higher order aberrations making blur detection difficult is yet unclear. This study investigates whether myopes respond to blur differently compared to emmetropes and whether filtering spatial frequencies in reading text influence accommodation responses. Accommodative functions were investigated using spatial frequency filtered text targets of two different sizes (N10 and N20). Monocular objective depth of focus (DOF), accommodative microfluctuations, and dynamic accommodation were measured. Subjective DOF after cycloplegia was also recorded with the same targets. Higher order aberration measurements explored optical contributions to blur. Peripheral refraction and accommodative lag were also measured to consider how in combination they might increase peripheral retinal blur for near tasks. Results showed that myopes demonstrated larger subjective DOF. Subjective DOF was larger when viewing the peak text spatial frequency in both refractive error groups. The optimum focus was more myopic for text peak spatial frequencies. Levels of spherical aberration were correlated with the point of optimum focus. Objective DOF and accommodative microfluctuations were larger in myopes when viewing the peak text spatial frequencies. Dynamic accommodation showed that while myopes were not poorer at initiating accommodation responses they had longer positive response times. Accommodative lag, although not different in myopes, increases the peripheral hyperopic blur experienced for near tasks. Conclusion: Myopes were poorer at using retinal blur cues to refine accommodation responses especially when viewing peak text spatial frequencies. Larger positive response times, DOF and accommodative microfluctuations in myopes resulted in accommodative error and hyperopic blur for near tasks. Spherical aberration, previously thought to provide a myopigenic stimulus, was not different between refractive groups and is unlikely to be large enough to enhance DOF during naturalistic viewing. Blur adaptation studies might consider using peak text spatial frequencies as adaptation targets to reduce accommodation differences in myopes and emmetropes. Optical treatment strategies aimed at correcting peripheral refraction to control myopia should consider the combined effect of accommodative lag which increases levels of hyperopic peripheral blur experienced by myopes.

Master of Science / Department of Psychology / Lester C. Loschky / The effect of blur/clarity contrast on selective attention was investigated in terms of how unique blur and/or clarity guides attention. Visual blur has previously been suggested to be processed preattentively using a dual-task paradigm (Loschky et al., 2014). Experiments 1 and 2 used rotated L and T visual search tasks with blur/clarity contrast being manipulated such that it was non-predictive of the target’s location. Each experiment was preceded by a legibility control study such that blurred and clear letters had similar accuracy and reaction times. This allowed for the results to be interpreted as changes in attention rather than difficulty identifying the letters because they were blurry. Results suggest that when non-predictive of target location, unique blur plays a passive role in selective attention in which it is ignored, neither capturing nor repelling attention to its spatial location, whereas unique clarity captures attention. The findings provide insight to the role that blur/clarity contrast plays in guiding visual attention, which can be implemented in visual software to help guide selective attention to critical regions of interest displayed on a computer screen.

No / Falls in the elderly are a major cause of serious injury and mortality. Impaired and absent stereopsis may be a significant risk factor for falls or hip fracture, although data from epidemiological studies are not consistent. Previous laboratory based studies, however, do suggest that stereoacuity is an important factor in adaptive gait. The present study investigates how acute impairment of stereopsis, through monocular blur of differing levels, ranging from 0.50 diopter (D) to a monovision correction affected gait when negotiating a raised surface in elderly subjects. Eleven elderly subjects (73.3 3.6 years) walked up to and negotiated a raised surface under nine visual conditions, binocular vision, one eye occluded and 0.50 D, 1.00 D and monovision correction (mean 2.50 D 0.20 D) with blur and occlusion either over the dominant or non-dominant eye. Analysis focused on foot positioning and toe clearance parameters. There was no effect of ocular dominance on any parameters. Monocular blur impaired stereopsis (p 0.01), with more minor effects on high and low contrast acuity. Vertical and horizontal lead limb toe clearance both increased under all levels of monocular blur including the lowest level of 0.50 DBlur (p 0.03) and monovision correction led to toe clearance levels similar to that found with occlusion of one eye. Findings demonstrated that even small amounts of monocular blur can lead to a change in gait when negotiating a raised surface, suggesting acute monocular blur affected the ability to accurately judge the height of a step in the travel path. Further work is required to investigate if similar adaptations are used by patients with chronic monocular blur.

Yes / Purpose - Blur adaptation occurs when an observer is exposed to continuous defocus. However, it is unclear whether adaptation requires constant defocus, or whether the effect can still be achieved when the adaptation period is interrupted by short periods of clear vision. Methods - The study included 12 emmetropes and 12 myopes. All observers wore full refractive correction throughout the experiment. 1D and 3D of myopic defocus was introduced using spherical convex lenses. An automated system was used to place the blurring lens before the RE for varying periods of blurred and clear vision during adaptation. Participants watched a DVD at 3 m during each 15 min trial. Visual acuity was measured using Test Chart 2000 before and after adaptation. Results - Blur adaptation occurs to varying degrees depending on the periods of incremental blur exposure. Significant improvements in defocused visual acuity occur with continuous blur, equal blur and clear periods, as well as for longer blur periods. However, longer clear periods showed reduced adaptation and this trial is significantly different to the other three trials for both defocus levels (p < 0.001). No refractive group differences were observed for neither 1D nor 3D defocus (p = 0.58 and p = 0.19 respectively). Conclusions - Intervening periods of clear vision cause minimal disruption to improvements in defocused visual acuity after adaptation, indicating that blur adaptation is a robust phenomenon. However, when the exposure to clear vision exceeds the defocused periods, adaptation is inhibited. This gives insight into the effects of real-world tasks on adaptation to blur. / Ms Kiren A. Khan was supported by a School of Optometry and Vision Science PhD studentship.

abstract: The depth richness of a scene translates into a spatially variable defocus blur in the acquired image. Blurring can mislead computational image understanding; therefore, blur detection can be used for selective image enhancement of blurred regions and the application of image understanding algorithms to sharp regions. This work focuses on blur detection and its application to image enhancement. This work proposes a spatially-varying defocus blur detection based on the quotient of spectral bands; additionally, to avoid the use of computationally intensive algorithms for the segmentation of foreground and background regions, a global threshold defined using weak textured regions on the input image is proposed. Quantitative results expressed in the precision-recall space as well as qualitative results overperform current state-of-the-art algorithms while keeping the computational requirements at competitive levels. Imperfections in the curvature of lenses can lead to image radial distortion (IRD). Computer vision applications can be drastically affected by IRD. This work proposes a novel robust radial distortion correction algorithm based on alternate optimization using two cost functions tailored for the estimation of the center of distortion and radial distortion coefficients. Qualitative and quantitative results show the competitiveness of the proposed algorithm. Blur is one of the causes of visual discomfort in stereopsis. Sharpening applying traditional algorithms can produce an interdifference which causes eyestrain and visual fatigue for the viewer. A sharpness enhancement method for stereo images that incorporates binocular vision cues and depth information is presented. Perceptual evaluation and quantitative results based on the metric of interdifference deviation are reported; results of the proposed algorithm are competitive with state-of-the-art stereo algorithms. Digital images and videos are produced every day in astonishing amounts. Consequently, the market-driven demand for higher quality content is constantly increasing which leads to the need of image quality assessment (IQA) methods. A training-free, no-reference image sharpness assessment method based on the singular value decomposition of perceptually-weighted normalized-gradients of relevant pixels in the input image is proposed. Results over six subject-rated publicly available databases show competitive performance when compared with state-of-the-art algorithms. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2019